Memory - RAM and Cache
The Midnight Question Archive
see the new: Motherboard, CPU and RAM Troubleshooting Flowchart
and Start Your Own PC Business
Copyright 2008 by Morris Rosenthal
Memory - RAM and CacheThe Midnight Question Archive see the new: Motherboard, CPU and RAM Troubleshooting Flowchart and Start Your Own PC Business Copyright 2008 by Morris Rosenthal |
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Troubleshooting your Laptop or PC
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See the new Troubleshooting your laptop or PC (May 2008)3/11/99(Q) I have bought 2 different sets of 4 SIMMs 8meg each neither have worked. First set was 2X32 60ns EDO ram, installed all 4 of the new 8meg SIMMs, system will not boot, no beep, no nothing. Finally got some documentation for the system, claims can use anything up to a 32meg SIMM, 70ns, page mode type. So get second set of SIMMS supposed to be page mode, again put al of the new mem in and system will just give long beep, pause, long beep, continuously. Is there a way to tell if memory is FPM or EDO? First set is marked EDO, second set is not. Victor (A) Well, 8MB SIMMs were always the most problematic, especially the single sided ones, but longtime readers of this page already know that. The main reason for this post is BIG NEWS (at least to me). IC Master now has their whole database online, with free registration to get in and use it immediately. This means you can now identify just about every chip and module you come across, and as those of us who've done any reverse engineering know, this book is the ultimate resource. www.icmaster.com Find out if that RAM is really FPM, EDO, SDRAM, etc... Morris 2/21/99(Q) It really started to take hold after I installed Win 98.... I would get invalid page faluts, blue screen of death thingys ect. because the case of the machine was for a P60...I figured that my full decked out system was asking too much power from the 145 watt power supply, I upgraded to a new case and power supply. After the new power supply the errors I get come much less frequently, but when I run games, and during cerain parts of windows, I either lock up, or get illigal operation things. I've noticed that it only really happens when I run games and things that require large amounts of system resources. Furthermore, I just got the game half life, and should be able to play it (with my system) at at least 640x800, but it's somtimes is too choppy. Also randomly durring the game the entire system locks up. Nat (A) Try running with just 1 32MB DIMM, and then just the other. Win98 stresses the system RAM more than any previous version, just like 95 had a way of picking on overheating CPUs. Really sounds like an unhappy RAM problem. (Nat reports RAM is it). Morris 11/13/98(Q) Does anybody want a 4MB SIMM (72pin) of Fast Page RAM? Hate to throw it out, but what do you do with something like this? As usual, if there are multiple respondents, it goes to the person with the best use. I'll pay the postage, just send your snail mail address. On the same subject, I get a lot of mail these days from folks trying to ugrade system memory and having trouble getting SDRAM of different vendors to work together, EDO RAM of different SIMM sizes to count properly, and problems mixing any of the above with each other or FPM. The memory game has gotten much more complicated than it used to be, with some system requiring EPROM SDRAM (LX chipsets), some 3.3V, some 5V (or 5V tolerant), some PC-100 rated, whether 10nS or 8nS, and on and on. The truth is, I don't know any good way of gauranteeing that your upgrade memory will play nicely with your old memory. The best approach, in case of doubt, is to start out by buying new the amount of memory you need (hopefully on a single DIMM), and if you can't use the old memory, give it to somebody who can. Believe me, you'll recover the value of the 8MB or 16MB you were hoping to save on shipping costs or gas. Now 32MB, that's another story. Morris (A) I too have 1 lonely 4 meg simm that came out of my son's 486. Can't do much with 1 but I am trying to rebuild a stripped down 486 tower that was given to me and the extra simm would at least get me one step closer. Allan 10/2/98(Q) I recently purchased a AMD K2-333 with 64MB RAM, as a single SDRAM DIMM. I had a couple 32MB SDRAM DIMMs around which I added. When the system booted, it only reported 32MB total! I removed a 32MB DIMM, it still said 32MB total. I took the 64MB DIMM out and reseated it, now I couldn't even get video. The DIMMs sat in kind of funny, after pushing part way, I had to manually lift the levers and then they'd kind of clunk into place. Do you think the RAM or the motherboard is ruined? Ken (A) It's probably OK. I'd take a breather from working on it, start fresh tommorow. Somehow, the industry has slipped back into some basic components like RAM becoming less and less compatible, to the point where you're safest buying whatever you think you might need with the motherboard and CPU. It is pretty cheap. All DIMM sockets I've worked with are designed so that the levers, which you open before inserting the DIMM, lock into place by themselves as the DIMM is seated properly. This can take a more than reasonable amount of force. If you're moving the levers manually, the DIMMs may be going in cocked, or not reaching the contacts fully. In case you might have damaged a socket, try your 64MB DIMM in another socket, the newer motherboards rarely require a particular bank to be populated first. (The next day, Ken reports he has his 64MB back and is standing pat). Morris 9/16/98(Q) (Repost from 7/31/98 with new info from reader) I just ordered a new Pentium grade motherboard. It is supposed to have two 2 DIMM slots and two SIMMs. I am using two16MB EDO SIMMs which the board will support. My question is what will happen if I also install two16 MB DIMMS along side with the much faster 10ns speed? Does one slow down the other, or as a 'rumor' I heard the faster ram will somehow damage the SIMMs (don't put much stock in rumors). Are their any performance characteristics to consider or is this all a case of "it depends what the motherboard book says"... Kevin (A) Everything depends on the motherboard. You certainly can never mix types, speeds, even brands, within a bank, but since two SIMMs or 1 DIMM makes a bank on Pentium class systems, that's not a worry for you. Motherboard support comes down to such specifics as "If Bank 3 (SIMM sockets 1 and 2) uses 2-sided SIMMs, Bank 2 (DIMM Socket 2) must be empty." That's an example from a specific motherboard, not a general case, but you get the picture. The best thing to do, if you want 64MB of fast SDRAM, is to by one 64MB DIMM (or two 32MB DIMMs) for around $60 and remove the EDO memory. By the way, the 10nS quoted for theSDRAM vs. the 70nS for EDO is comparing apples and oranges. The 10nS pertains to sequential access pipelining setup time, the random access is about the same as the EDO. Morris (A) The problem with using EDO or FPM along with SDRAM is that EDO/FPM is a 5 Volt chip, the SDRAM is Almost always 3.3V (many macs excluded), AND that the memory bus is often shared. So, the 5V output from the EDO/FPM is showing up on the 3.3V output of the SDRAM. Strangely enough, this works for a while, but uually leads to increasing memory errors after a couple of months. Then, death by parity error! Some SDRAM chips are 5V tolerant, a couple are listed below.
Paul 9/3/98(Q) I have added memory to a 386SX computer as per your instructions on page 111 of "The Hand-Me-Down PC". However, when I restarted the computer and check the Device Manager Properties, it still states 4MB of RAM. There is no indication that the additional RAM was added. Am I missing something in the installation? Bill (A) It depends on what memory was already installed, whether or not the motherboard can deal with the new memory (9 chip, 3-chip, parity), and whether or not the un-used SIMM slots ever worked. Try sticking a couple 4MB SIMMs in Bank 0 and see what happens. Also, Device Manager is a Win 95/98 feature, and I don't recall 386SX's being Win95 compatible. Morris 8/24/98(Q) - Not really a question, but good stuff (MR) I'd like to pass on a quirky and interesting experience I had with my FIC-PA2007 motherboard. The PA-2007 is a popular Socket 7 motherboard with Award Bios and 1 meg of onboard cache. It has 4 SIMM slots and 2 DIMM slots. I got it in my craw to upgrade from EDO RAM simms to SDRAM dimms. I go out to a reputable local computer store and buy 64 Meg of Toshiba brand 168 pin SDRAM. I go home and remove the SIMM's and put in the Toshiba SDRAM. It starts booting up "quirky." One out of three times....the POST sequence freezes at the hard drive detection phase and says: Hard Drive failed error message!!! This was in January and I had a fairly new Quantuum 6.4 gig Ultra DMA drive. I tried tweaking every possible BIOS setting and combination. I even tried FDISKING and reformatting. (DUH). I finally tried the obvious...the put the EDO SIMMS back and took out the SDRAM. La-di-dah! No problem whatsoever. I took the Toshiba RAM back and they gave me no hassles but had questioning looks as "Toshiba has been VERY good for us qualitywise." And I'm sure it is. Two weeks later...I was surfing around on the net...and I believe it was at MicroXpress's homepage that I stumbled upon a Tech Support sheet on RAM. It said that the early Award BIOS versions of the FIC-PA2007 were fussy about SDRAM and to use non-segmented RAM. I called up the Crucial Tecnology (RAM retail sales division) ofMicron and the guy there hunted around in thier Oracle database for a while and recommended an SDRAM module with SPD (Serial Prescence Detect) EPROM on it. I get it in the mail. Voila! No hassles. Up in 4 minutes flat. Later I read on another homepage something that implied that the VIA chipsets do better wtih Crucial, Samsung or Hyundai RAM. It also said that the situation with SDRAM (compatibily problems) is getting so fussy that the motherboard manufacturers are going to have to bite the bullet and start recommending ** specific ** brands of RAM. By the way I have two AMD-K6 233's in FIC boards. They run very fast and reliably and I have had no hassles other than this little skirmish. Ben (T) Thank you Ben for this well documented account. I've suspected as much, but I haven't put the time into it that you have. Actually, I ran into problems with SDRAM in a K6-233 I built for my new book. I was able to install Win98, but it would give all sorts of flakey errors after the fact. I guessed RAM, stuck in some old FPM 32MB SIMMs, and it worked fine. The funny thing, is I couldn't see a enough difference in performance to get excited about, so I left it in. Morris 8/19/98(Q) I have a Matsonic MS-5010 (Running the 82437VX Chipset) it has 4 72pin slots, and 2 DIMM slots. I am guessing that the 32MB DIMM I have in the system now is not SDRAM. The documentation for the board tells me that it does support SDRAM, and there is an entry on the BIOS report at boot that says: SDRAM Rows: None. Recently, Best Buy put their 64MB SDRAM modules on sale for $70 so I picked some up, however when I installed it in my system, it only counted to 49MB. I then removed my 32MB DIMM from the first slot, and tried to install the memory there, still counted as a 16MB module. Well the tech at Best Buy tried 64MB SDRAM DIMMs, 32MB SDRAM DIMMs, and he tried multiples of both PNY and their "Bulk" memory. None of it counted past 16MB, except the module I started with. I called the vendor, and they told me that the board does not support EPROM Memory, all I can think of is that this is some type of newfangled memory thing, or the tech support guy was full of hot air. He also said that .... And I quote, "EPROM stands for error correction something or other." Last time I checked it was an Erasable PROM. I would really like to increase my memory to at least 64MB and 96 would be great! Eric (A) The tech might have meant ECC (Error Correction Code), which is a big step up from parity for catching and correcting errors. Or, he might have meant EPROM equipped modules, which are required by LX chipset and some other systems. This EPROM, really an EEPROM (Electrically Eraseable PROM) stores a desciption of the DIMM timing/speed, capacity and voltage. One thing you can try is getting some cheap 72pin SIMMs. Another is to try EDO DIMMs, maybe the larger SDRAM modules were never tested on the board and just won't work. Since you have the latest BIOS loaded on your motherboard, you don't have too many other options. Morris 8/13/98(Q) I'm using Microsoft Windows 98, with 48 MB RAM and the cpu clock 166 MMX. Yesterday, when I'm doing some work, it become 'hang' and cannot proceed anymore. It cannot be reboot by ctrl + alt + del, so I turn it off for a while and switch back. When the windows is coming, it say that the extended memory driver not installed and also about VFAT problems. I'm try to start the system again, but the same problem is happend. Lastly, I have to format my hard disk, but when I'm finished install back my Windows 98, it must be restart for the hardware initilization. The same problems happend again. "VFAT Device Initialization Failed. A device or resource required by VFAT is not present or is unavailable. VFAT cannot continue loading. System halted." Mohd (A) Actually, it has the sound of a RAM problem to it. VFAT runs a couple of different cache stacks in system memory to speed up 32bit disk access. Since you have 48MB, you have enough memory to try removing some. If it's 3 16MB DIMMs, take out the DIMM in Bank 0 and move the other two down. You might also try restoring Setup defaults, in case the memory timing was set to fast. Otherwise, I might suspect a virus. Morris 8/5/98(Q) One fateful day, my P200 MMX with 32 MB RAM decided not to boot at all, and displayed the following symtpoms: No POST beeps at all, Blank screen (I havn't got a dual colour LED, so it's always green). There are two hard drives. If I plug in a hard drive (primary or secondary), it will do nothing at all. If I remove the IDE cable, but leave the power connected, the drive spins. This happens with both drives. I have 4 8Mb SIMMS, I have tried one pair, then the other, but no difference. I bought a brand new motherboard, upgrading from a VX to a TX chipset, but this did not solve the problem. The new motherboard has on board graphics and on board sound, which eliminates my cards, so I know it can't be these. I would suspect the power supply but the processor fan spins and the hard drive spins with no IDE connected as above. David (A) Would almost have been easier to troubleshoot with old motherboard, you still may want to. In a "no video" case, the first step is always to simplify the system to the bare essentials, and get video back. This means removing all adapters (except the video card), disconnecting all drives, and leaving one bank of memory (Bank 0). If you get no video, at this point, the prime suspect is usually the RAM or the video card. Since we don't know if your new motherboar is good, it doesn't eliminate anything. Bad RAM will often produce beep codes, so the first option is another video card, or try yours in another PC. Next, try RAM from another PC (your new motherboard could have smoked your RAM). Try your monitor on another PC. At this point you're down to powers supply (the drives working doesn't mean the motherboard power is OK), CPU (rare, as you guessed), or the motherboard (also pretty rare). There aren't any shortcuts. Morris 7/31/98(Q) I just ordered a new Pentium grade motherboard. It is supposed to have two 2 DIMM slots and two SIMMs. I am using two16MB EDO SIMMs which the board will support. My question is what will happen if I also install two16 MB DIMMS along side with the much faster 10ns speed? Does one slow down the other, or as a 'rumor' I heard the faster ram will somehow damage the SIMMs (don't put much stock in rumors). Are their any performance characteristics to consider or is this all a case of "it depends what the motherboard book says"... Kevin (A) Everything depends on the motherboard. You certainly can never mix types, speeds, even brands, within a bank, but since two SIMMs or 1 DIMM makes a bank on Pentium class systems, that's not a worry for you. Motherboard support comes down to such specifics as "If Bank 3 (SIMM sockets 1 and 2) uses 2-sided SIMMs, Bank 2 (DIMM Socket 2) must be empty." That's an example from a specific motherboard, not a general case, but you get the picture. The best thing to do, if you want 64MB of fast SDRAM, is to by one 64MB DIMM (or two 32MB DIMMs) for around $60 and remove the EDO memory. By the way, the 10nS quoted for theSDRAM vs. the 70nS for EDO is comparing apples and oranges. The 10nS pertains to sequential access pipelining setup time, the random access is about the same as the EDO. Morris 7/28/98(Q) I just finished putting together the following system: AMD K6 300 w/MMX, 4 mb agp video card, 3d sound pro sound card, 5.1 gb WD hard drive EIDE, 96 mb edo ram. I installed Win98 with no problems, and everything was working fine for a few days. Then (of course) after a few days, the system decided not to boot.....I would only get beeps from the internal speaker. I looked up the meanings according to the # of beeps, and it seemed like a memory problem (loose chips/bad chips?). I removed and replaced the same chips....and that problem went away. Now, I get erratic mouse errors such as "can't detect mouse" (all connections seem ok), and I've tried 2 different mice on both the ps/2 and serial ports. Also, when the mouse is working, the cursor will start jumping all over the screen....and then locks up. Brian (A) Did you unplug the power supply from the wall, or from the motherboard, before you reseated the memory SIMMS/DIMMS? If not, it's possible that you did a little damage to the motherboard, since ATX power supplies are never really "off". I mention this, because I'm on a crusade. It could also be bad memory where the mouse driver sits getting by the memory check, so you could try rearranging the SIMMs again (unplug the cord from the power supply first). You should also make sure that the RAM is recognized as EDO in CMOS Setup, and maybe try slower timing for it. Morris 7/24/98(Q) I have over 100, 30 pin SIMMS we took out of old computers in my offices. I will use them as spares (keeping like kind with like kind) on the remaining computers that can use them. I know that some are 256K and some are 1M and so on. Unfortunately, only a few are labeled. In the small print on the chips it says ....256.... or ....1M.... I have many more that I can't tell from the numbers what they are. Is there a place on the web where they list SIMMs, their capacity, and **most importantly** the Manufacturer's part numbers??? I should be able to find memory speed as well by looking at the MFG PN. I just don't know how to read it. Example "4100 T9430-7" What the heck is that??? Channel (A) 4100 is probably a 4megabit X 1 chip, 4 megabit deep at at 1 bit wide, meaning eight of them on a 30pin SIMM would give you 4MB, no parity, certainly the "-7" is 70ns. The only SIMM I have lying around out of a box at the moment uses eight 514400 chips, which are 4megabit chips each 4 bits wide and 1 megabit deep, meaning eight of them on a 72pin SIMM gives you 4MB. I have never seen a universal system for identifying memory chips, different manufacturers use different codes. If you get a hold of an "IC Master", you can look up each new chip you encounter and do it that way. What can you do with all those little SIMMs, I've found myself throwing out 4MB 72pinners. Morris 7/14/98(Q) Here's the situation: I have a FIC 503+ motherboard with 1 MB of cache and which support a 100 Mhz front side bus speeds. I have PC-100 SDRAMs. I have a AMD K6 233 Mhz processor. AMD and FIC list (as an acceptable bus speed) 66 Mhz for that particular speed CPU, which works out to be a multiplier of 3.5. I, wanting to use 100 Mhz bus speed need a multiplier of 2.33 - not an option. I only have 2.0 and 2.5. So I either take a performance hit at 2.0 or I overclock at 2.5, run my chip at 250 Mhz and gain a 100 Mhz front side bus. Will it work? Kevin (A) I try to avoid entirely half-baked answers, but this will certainly be one. First of all, the standard disclaimer "Only the AMD K6-2 processors are certified by AMD to run at the fast 100MHz bus clock. The standard AMD K6 was designed and rated to run at a 66MHz bus and overclocking to run at 100MHz bus is not recommended." Now, from what I've gathered via some web research, the 100MHz bus isn't all that stable unless you buy memory modules that use 125MHz memory chips. Whether or not there are modules rated PC-100 that don't use these chips (8 nS), I can't say. Also, there appear to be motherboards out there, especially in Socket 7 world, that were designed with independant settings for the bus and CPU, the need being driven by the 75MHz bus for one of the Cyrix chips that doesn't give you a nice way to divide down to the 33MHz needed for the PCI bus. At any rate, the consensus seems to be that the more flexible the motherboard (i.e. the more ways they give you of clocking things differently) the better off you are. In Intel motherboard world, for Slot 1 and Slot 2 CPUs, your main worry is just getting decent quality PC-100 SIMMs. Only P-II CPUs of 350MHz or higher are designed to work with the 100MHz bus in Slot 1, no Celerons need apply. The new Slot 2 Pentium II Xeon CPUs are all designed for the 100MHz bus (not to mention L2 cache running at the core CPU speed). Morris 7/3/98(Q) Have you heard of ecc ram .. It has replaced fast page mode ram ..for the 486 dx4 100; they have stoped producing .. 41c1000 David (A) ECC RAM hasn't replaced FPM (Fast Page Mode), it is an option on any memory type for Error Code Correction. Unlike parity checking which tells you that a bit is wrong in your byte but not which bit, and misses errors if two different bits flip, ECC can detect multiple bit errors and fix single bit errors. If it hasn't changed since I took a digital course 15 years ago (Hamming Codes?), you need three extra bits on a single byte to do ECC, but the number of extra bits required goes down as the word size being checked gets bigger. ECC memory is more expensive since more bits are required, and needs a memory controller that supports it. However, as overall RAM prices have dropped, it's gotten a lot more common, particularly with high performance systems, like the 100MHz memory bus. The EOS version (ECC Onboard SIMM) doesn't require an ECC aware motherboard, but is overkill for home PCs. For your initial question, if you can't find FPM, get EDO, which is backwards compatible. Morris 6/29/98(Q) Being the typical male, I attempted to upgrade the memory in my sisters PC, failed, dinked around, and then crashed altogether!!!!!!! Of course I didn't seek any assistence until I crashed completely. Her system is a Pentium 133 w/16 meg EDO. (2 8's) I purchased a 32 meg simm (edo) and installed it. No change in mem size. I've since learned from your Q&A page about the 64 bit memory bus. My first mistake, but not fatal. I then removed the two 8 meg simm's and installed the 32 meg only. Well, no boot, nothing but a series of beeps. Ok, that didn't work. Well enough though, I went back to the two 8's, and it worked fine. Then comes the BIG mistake. I tried one 8 and one 32. Same non-boot condition. However, this time when I went back to the two 8's I still get the same non-boot series of beeps. I reinstalled the 8 meg simm's again in the event that I wasn't making good contact with the socket. No change. I assume that the series of beeps indicates a specific problem? I actually removed all memory, and tried to boot just to see if I would get the same series of beeps. I did. Brad (A) Uh-oh, sounds like something may have smoked. That the single 32MB wouldn't work alone is correct - for the 64bit bus you need two 32MB SIMMs. You can never mix different size SIMMs within a bank, and though I'd never come across this doing damage, I've never done it on purpose to try. I've have seen missmatched SIMMs recognized by the system, with the larger SIMM registering the same capacity as the smaller, or both at the same fraction of capacity of the smaller. Hopefully, the problem is that the 8MB SIMM flaked out, but you may as well try taking the 32MB back where you got it and ask them for two matched 32MB EDO SIMMs, and ask them to show you in a bench system that they work. Then take them home and try them, and if it's no go, something on the motherboard is fried, and unless it's the CPU, it's not repairable. (It turned out nothing had smoked, the later boot failure was due to a dislodged video card). Morris 6/19/98(Q) You talk about BSRAM when talking about the Celeron (Catching up on the new technology) but don't talk about it in the ram section. What is it? Dave (A) The 512K L2 cache that comes as part of the Pentium II cartridge is Burst Synchronous RAM (BSRAM). According to the last time I visited the Intel site, it operates at exactly half of the Pentium II speed, i.e. with a 300MHz Pentium II, you'll get 150MHz bus speed for accessing the L2 cache, with a 400MHz PII, 200MHz cache access, double any Socket 7 CPU L2 scheme. In the pictures in the "CPU's and Heatsinks" section of "Building the new PCs", you can see that the Pentium II is a package, with the L2 cache integrated within, while the Celeron is basically a CPU mounted on a ciruit board. Morris 6/11/98(Q) Is there anyone in the country who repairs SIMMs. I have 2 32M 72 pin SIMMs and neither check out ok. I would hate to just throw them away. Pete (A) I suppose there are still people who repair SIMMs, but at 32MB, they're worth less than $40 apiece new, so it couldn't be cost effective. Also, since the chips really should all be matched, repaired SIMMs (and this goes back to the bad old days), tend to fail very rapidly, or not work in a given PC at all. The vast majority of bad SIMMs I've seen in my life have had mixed brand or speed chips. Morris 5/5/98(Q) On an Acer Across computer that I am trying to repair, I keep getting this message at boot-up, "Ram Parity Error, Press Esc to continue". I used the restore disk and CD-ROM that was to put the computer back to the way it came from the manufacture, but the message keeps appearing. How can I correct this problem? Bill (A) That's a real parity error, the RAM has failed. Try replacing it, or you can gamble on turning off parity checking in CMOS (if it's an option) and running a software checker to see if the RAM is really OK. Remember, with 3-chip SIMMs there's a real good chance the error is on the parity chip, with 9-chip SIMMs it's down near 10%. Morris 4/28/98(Q) I just purchased a 128 SDRAM chip. I installed in my P11 computer and the got a blank monitor. I pulled out the SD chip and put back my old ram and the computer worked just fine. I spoke to a tech and he said I need to set the correct voltage on my motherboard to same as the chip which is 3.3 volts.How is this done? With jumpers or ? Did I fry my new SDRAM if the voltage was not set properly? Grant (A) Haven't had it come up yet, but votage settings are done through motherboard jumpers. CMOS can't be used to set voltages, you'd never get out of the starting gate if they were wrong. I'd be surprised if you could fry anything, but on the other hand, SD RAM isn't supposed to work in systems that don't explicitly support it. I'm not familiar with the P11, but if it didn't ship with SDRAM, it won't support it. Morris (A - from reader) Yes, the jumper has to be set to 3.3. My Triton 3 m/b has a 5/3 pair of jumpers. Regarding his screen coming up blank, I had this happen with a chip that did not want to go right down in the socket. I took it to a friend to check it out and he managed (after some trying) to get it socketed on his board. Wes 3/17/98(Q) What's so special about Compaq memory? My neighbor has a Presario 5528 she's trying to run Win95 on with only 8M. There are two empty 72-pin SIMM slots in there. I stuck in a couple of 16Mers I had laying around, and nothing happened. I mean, NOTHING. Went down to Computer City, where she bought it, to see what the story was. Big mistake. Their first reaction was that you had to match the SIMM contacts with the socket contacts -- tin with tin, gold with gold, etc. Made no sense to me (seems like gold ought to work anywhere) but what the hell, he's the dealer, right? Well, to make a long story short, he tried every SIMM in his stock with varying, but unsuccessful, results, and finally gave up and told me to call Compaq. A couple of Computer Shopper memory dealers said they knew what the difference was, and were happy to sell me something guaranteed to work, for just about twice the going RAM rate. A local computer-show memory guru said he also knew, but was pretty vague about describing it to me. Mike (A) Gold and Tin is strictly a long run issue, doesn't effect whether or not something will work when the parts are new. There are many more types of memory out now than just a year ago, and big stores tend to stock only the latest, which may be a problem. You've got FPM (Fast Page Memory) the old standard in single and double sided SIMMs, EDO (Extended Data Out) and SDRAM (Synchronous DRAM), maybe one I've missed. They also come in a variety of voltages now. The point is I don't know how foward/backward compatible they all are, not having played with enough of the newest machines. I've been intending to do the research and post a page on the subject for a while, maybe your question will motivate me. By the way, there's always the possibility her SIMM slots are bad. For a good run-down on memory (from Kingston, suggested by Steve) goto: http://www.kingston.com/tech/memo13.htm Morris 1/2/98(Q) I have a 75 Pentium and a PCI Bus & ISA Bus mainboard. Anyway, I didn't want to pay for the installation of the memory because I thought, hey, I can put it in, and I did. I even took one out and took it to the store and had it tested, for free, and found it was a non EDO and non parity, whatever that means. The problem is, when I rebooted and checked the properties, it still shows 16 mb instead of 32 (oh yeah, I upgraded from 16 to 32, got the two sets and all). So I called Best Buy and talked to the tech and he told me I needed to make a change in the computer set up. The where? He told me not in my Windows 95. Now in reading some questions, I believe I need to reconfigure the cache to 512K at least? E'va (A) Lets review here. You have a 75MHz Pentium with 16MB, which implies that you have two 8MB SIMMs, or 8MB hardwired to the motherboard and two 4MB SIMMs. At any rate, most 75MHz motherboards were built with four 72pin SIMM slots, which are each 32bits wide. A Pentium has a 64bit memory bus, so requires two 72pin SIMMs per bank. If I read you correctly, you have purchased two new 8MB SIMMs, and installed them. What I don't know is whether or not your system is counting 32MB on boot, or if it ever produced a "CMOS Memory Missmatch Error", insisting you enter CMOS Setup. If it hasn't, your system simply doesn't see the new memory, and there is nothing you can change to correct that. If it did, you don't actually need to change anything when you enter CMOS Setup, the change is automatic, just do an "Exit and Save". You can't change the amount of cache installed in CMOS (a seperate problem not affecting you're memory count). Cache is purchased separately, but most 486 motherboards only suppork 256KB of it. Did you ever take out your original SIMMs and try the ones you purchased, to see if your PC would still see 16MB? Here comes the problem - 8MB SIMMs are the most problematic of all SIMM types, coming in single and double-sided varieties, along with further variations (you've encountered the parity and EDO questions). All things being equal, I've had terrible luck mixing 8MB SIMMs on older motherboards, but 16MB SIMMs, which cost very little much more these days, work pretty consistently. Morris 12/9/97(Q) I have a 486-100 motherboard. It has 4 30-pin slots and 3 72-pin slots. There are 4 4-Meg 30-pin simms allready in it, giving it 16MB of memory. What I need to do is upgrade the memory to 32MB. Is this even possible? If so what memory config should I use? Mathew (A) It's certainly possible. If you actually have a manual, stick with the configurations they suggest, but otherwise your best bet is to try adding one 16MB SIMM to the first 72pin slot. If the two types of SIMMs don't want to play together, you can add a second 16MB SIMM and take out the 30pin SIMMs. Remember, since the 72pin SIMMs are 32bits wide, you only need one to make a bank on a 486. Many of the older boards don't support SIMMs greater than 16MB anyway. Morris 12/2/97I have a 486DX/33 computer with 16 megs RAM. I want to upgrade the RAM to 32, but I'm not sure what to do. I don't know if my cache is large enough, and I also don't know the difference between "EDO" and "regular" Ram SIMMS. Can you shed a little light on what I need to do and what information I need to complete the upgrade? Jeff The standard suggested amounts are 64K cache for 4MB, 128K for 16MB and 256K for 32MB. The additional RAM will still work and still give a big performance boost even if the cache is undersized. Since cache effectively provides a moving window of super fast memory over your main memory, the benefit (or lack there of) is highly dependant on the type of application being run. Extended Data Out (EDO) SIMMs support a protovcol that can save a wait state over older Fast Page Ram Simms, but your motherboard must explicitly suppport the option for any benefit to occur. Your 486/33 board almost certainly doesn't. Morris 12/1/97(Q) Composite question drawn from several similar questions over the weekend. I have just upgraded my PC with a new motherboard (or hard drive, or sound card, or modem), and now nothing come up on the screen, (or the system freezes after counting RAM without beeps or an error message) on boot. How do I proceed? Composite (A) In all instances, when you can't get as far as an on screen error message, you should strip the PC down to the bare bones and see if the problem goes away. Bare bones requirements to light up the screen are a motherboard, CPU, one bank of RAM, power supply, video card, monitor and keyboard. If you still can't get as far as text on the screen, one of these parts is bad, or improperly installed. Once you have a "live" screen, start putting the other parts back in ONE AT A TIME, until you either find the problem, or have a working system. Morris 10/23/97(Q) I would like to know if there is a way (formula, program) that I could convert Hexadecimal address to a decimal address? I am having memory problems with a 486 system that gives me a specific memory address in hexadecimal that HIMEM found problem with. But is seems to be intermitant and I can't trace it. Error occurs sometimes. I changed memory and I've been getting problems with it at several different addresses. I am begining to suspect the motherboard. I did test the memory with RAMEXAM from Touchstone's Checkit. I also tested the original memory in a different system, no problems. Arkidusz (A) Sure, you can use the "Calculator" under Windows or Win 95 "Accessories". However, since the computer actually does everything in HEX, I'm not sure where converting to decimal is useful for troubleshooting. You could try adding a wait state in the CMOS Setup to see if it helps, or dissable external (L2) cache, which will sometimes produce errors (not to mention sometimes covering errors if not dissable when memory checking is run). In the end, the most significant thing the address can tell you is which SIMM the problem is on, if it is indeed a hardware issue. Just remember to add 8 bits per SIMM for 30-pin and 32 bits per SIMM for 72-pin. Parity doesn't count here. Also, run the motherboard test in Checkit which tests the CPU and address lines a couple hundred times. Morris 10/12/97(Q) I have an 486 computer with two 72 pin 4Mb SIMMs 60nS, when I put two 4Mb SIMMs 70nS extra in, DOS works ok, but Win 95 does not start up. I've tried to put only the two 70n and it works ok. So all of the SIMMs are working and have the same number of chips (no parity) on them. The handbook of the motherboard only say that bank 1&2 and 3&4 must be the same type of simm and no jumpers needs to change. Gersom (A) You might try going into the CMOS Setup and adding a wait state, or trying any other memory compatability options they offer. DOS is somewhat less demanding on memory than Windows 95, which often brings to light minor incompatabilities when installed. Also, I've had e-mails lately asking about problems with mixing EDO and regular Fast Page SIMMs, so if your new SIMMs are EDO, that could be the problem. There is also the possibility that your second bank of SIMM slots is defective (well, the address lines or buffers), and that the problem just doesn't show up unless it is exercised. Outside of experimenting with settings, and re-arranging the bank order, there's not much you can do without trying new SIMMs. Morris 9/28/97(Q) Thanks for the quick response to my problem! I did change the VLB controller setting to the greater than 33 setting and again all seems to work very nicely with write-back on the CPU cache disabled and write-through inabled. One last question, am I really taking that big of a performance hit but going with CPU internal cache as write through? I ran a program call Dr. Hardware on the system and with write-back it said the system was almost 25% faster than with write-through. A friend told me that it is because the test fit in the 16k cache and thats why I saw the large difference, but since most programs wouldn't "fit" completely in the cache the performance "hit" wouldn't be that bad. Is that true? Bob (A) It's part true. Often times code is run in loops, whatever the application, and these loops are often less than 1K, so fit handily in cache. The old propaganda said that a CPUs have an internal cache hit rate of over 90%, but I'd assume thats gone down some with 32 bit code. Internal cache of the 8KB or 16KB variety is generally regarded as "instruction" cache, while the external, or L2 cache is more suited to tracking main memory. The most important measure of performance is what you notice in applications, though I would occasionally put a stop watch on how fast a program loads or executes some lengthy function when I was evaluating hardware. Morris 9/23/97(Q) I own a Packard Bell Legend 233+, upgraded to a 486DX266 and the latest available Phoenix bios (dated 1996, to suppport Disk LBA). The PB430 motherboard originally had 4 meg of memory. I am currently running Win 95a and using 72 pin non-parity SIMMS and a motherboard integrated Cirrus Logic CL-GD5422 video w/512k memory. When I run with 16 meg OR LESS (with any combination of memory, ie: with or without the motherboard memory) of memory the system appears to run as expected with the amount of memory it is using. When I increase to 20 or 24 meg, the system (especially the video) slows to a crawl. WinTune 97 shows about a 50% performance drop from when the system has 16 meg to when the system has 20 meg. Richard (A) I'm skipping my reply, which wasn't, uh, exactly right, because Richard chased down the following answer for himself: I researched the BIOS as you recommended. It turned out that with the motherboard and only 128k of L2 cache the performance drops due to the way Win95 address memory. This is a quote from: http://www.firmware.com/pb4ts/p410cach.htm "If more memory is installed than can be cached, performance can decrease. This performance decrease can be significant with WIN95, since it allocates memory from the top.
and from: http://www.firmware.com/pb4ts/p4hs10.htm "WIN95 runs very slow - DOS programs seem to run at normal speed - This can be caused by an improper match between RAM size and external cache size. Disable the external cache in CMOS setup to see if it speeds up. 32KB cache can handle 4MB of RAM, 128KB of cache can handle 16MB of RAM, and 512KB of cache can handle 32MB of RAM (note that this applies only to these (PB410 and 430) motherboards). This can affect WIN95 much more than DOS programs possibly due to WIN95 allocating memory from the top." Richard (via Morris) 9/22/97(Q) I would like to ask you a question about those two error messages on CMOS Setup. After putting 16 mb RAM chips into 486DX/33, I received an error message: CMOS memory size mismatch, and then was asked to run setup. According to the manufacturers' website, I was told to go to CMOS Setup to choose 'WRITE TO CMOS AND EXIT' without making any changes. Then I rebooted it and I received another error message: ONBOARD PARITY ERROR ADDR (HEX) = (0000:0002) SYSTEM HALTED. What caused those problems ? What are the solutions? Darryl (A) The first error, "CMOS Memory Size Mismatch", is expected, and simply means that the system detects a different amount of memory than was present at the last boot. Since memory detection is automatic, the only thing you need to do is tell the CMOS to save the changes. The ONBOARD PARITY ERROR is serious, but it could be that your new SIMMs are non-parity, and you have parity checking enabled in the advanced options of the CMOS settings. If you bought the cheapest SIMMs you can find, they're non-parity, another indicator is an odd number of chips per side of the SIMM. If your motherboard is very old, you might REQUIRE parity SIMMs, and will need to exchange the ones you have. Morris 9/9/97(Q) My Pentium PC gives me quite a few GPF's and I really don't know what I'm suppose to do about it. When I click ignore nothing happens and when I click details I get a lot of numbers and letters that I have no idea of what to do with. Could you give me some information on what I should do or what a GPF means? This happens in almost any application I run from time to time. Cathy (A) GPFs (General or Global Protection Faults) are basically memory management errors. When they are entirely consistent (always happening at the same place), they are usually caused by a corrupted piece of software, normally the bit you just clicked on. When they are random, it's usually a hardware memory problem, whether cache or main memory. Since the only route for determining the exact problem is swapping out parts, reinstalling scads of software, or playing with diagnostics, I generally advise people who have it as an infrequent problem on an out of warranty machine to wait until it gets better or worse. Beleive it or not, it occasionally gets better! If the PC is in warranty, try calling the manufacturer, but they'll probably make you reinstall all your software before trying anything else. Morris 8/19/97(Q) I have a Gateway 2000 486 DX 2 66mhz system that used to have 128k of asynchronous (sp?) L2 cache. Someone that looks like me got the bright idea of upgrading the L2 cache to 256k. At the same time, I added a new harddrive requiring the installation of a new controller. At any rate, my system now has zero cache and cache is not indicated at bootup. I have verified this with two software products "CacheCheck" and "Snooper." I pulled the "new" cache chips and it still has no L2 cache. I have checked SETUP and verified that cache is enabled. I did notice that one of the "new" cache chips had a leg folded under when I removed it. Whether this happened on installation or removal, I am not sure. Did I fry my cache permanently? Stephen Straighten the leg (CAREFULLY) and put it back in. Common problem. If that doesn't fix it, one of the chips has failed, which may just be coincidence. You could go back to 128K, it really shouldn't make much difference on a 486, but you'll have to reset any jumpers you changed when you upgraded to 256K. Morris 7/31/97(Q) I have a Packard Bell PC with a 486DX2 and 24mb ram that I am trying to upgrade to Win-95. As soon as I begin running the setup, I get an error message telling me that I need to disable a program called CDREMAP.EXE This program is on my hard drive and is mentioned in the autoexec.bat as an LH line. Before I disable the program, I would like to know if it will cause harm to do so. So far I have been unable to obtain any info on this, even from Packard Bell. Also, what is an LH line? Derwin (A) LH is short for LOADHIGH, the DOS command that lets device drivers be placed in upper memory areas to conserve program memory (to 640 KB). Run the DOS program MEM/C |MORE, to get a look at your memory allocation. The program CDREMAP sounds like it is remappin your CD drive letter to something other than the next drive, which would be normal. Rem it out, but don't be surprised if your CD drive changes it's letter designation. Morris 7/30/97(Q) I have a very old 286 motherboard that I found at a thrift shop (never used!) that I have been building up recently out of spare parts, and have a quick question. First of all, the board has 36 256k Dram chips socketed (HY53C256LS) on the main board, which should account for somewhere in the range of 8-9 meg of memory. The problem I am facing is that I cannot access that memory. I get the first 640k, but no extended memory, even after trying innumerable CMOS settings. On POST I also get a displayed 0k of extended memory. Any ideas on what is going on with this mighty wonder? Jon Got some bad news. Your 36 - 256k chips are only 1bit wide, so it take 8 to make 256KB, or 9 to make 256KB with parity. That means the 36 chips give you a total of 1MB, so your CMOS is count is correct. Morris 7/23/97(Q) I have another question...my computer has suddenly gotten sluggish...I've checked the conventional memory in DOS and in shelling out to DOS under windows...it is above 550 on both (DOS is higher, of course.) What could be the cause of the "slow down?" My mouse is even sluggish and sometimes I get thrown out of AOL with an error. I have 16meg of RAM installed. I haven't installed any new software...It's a mystery to me....can you help? Anon Super common problem, 99% of the time the system is out of turbo or internal cache dissabled in CMOS Setup. Morris |