I just finished "fixing" a pc that was having memory problems. This was an old 486DX-33 with 12MB. Anyhoo, it was getting "invalid vxd......" error when booting win95. Also when trying to boot to safe mode I was getting memory errors in different addresses when Himem.sys tested the memory, saying that himem could not be found. This did not occur on every boot howevr the former error always did untill the registry was replaced with a back up. I'm going on here about windows. I found the error to be memory related, so I removed the simm in bank 3. (bank1 4mb, bank2 4mb, bank3 4mb, bank4 empty) This did the trick and I had no more problems. I assumed it was the simm, but when I tried to replace it with any of two other simm I had lying around I got the exact same errors.(the himem errors seem to have different addresses but are otherwise the same)
Is this a problem with the third memory bank? I doubt all three simm's were defective, although I know one reads as 4mb, when it is actually 8mb.
If it is the bank can I do anything about it? Or am I stuck with only two banks? Is there any way to test the bank? Possibly it could be incompatible memory I guess. Would incompatible memory cause this type of error? ie. the same error?
Also it's an old AST board and I haven't been able to identify it yet. I'm not sure who manufactured it. http://www.PCGuide.com/ubb/rolleyes.gif

It's most likely incompatible memory. 72 pin SIMMS were made in EDO, Fast Page Mode, Parity and Non-Parity. Mix any of the types and you'll get memory errors.

See if you can swap them around using the first two banks, and maybe you can find out which ones are compatible. Then see if you can put together enough that will work together to add some to the third bank, and see what happens. I would doubt that the bank is bad, but it is a possibility, stranger things have been known to happen...If you can get enough memory together that works in the first two, adding some of it to the third one should tell you if the bank is bad, or if it's a compatibility issue.

You can test individual chips by using only one bank, and swapping the chips out one at a time, only booting far enough to let himem test the memory. Soon as one gives you an error, you know either the chip is bad, or it's incompatible with the other chip. Label each as you go, and you can find out what will and what won't work. It's a tedious and time consuming process, but it works. Keep one original chip in, and don't remove it. That way you know what's compatible with it.

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If you had everything...Where would you put it?

Computer Information Links (http://www.geocities.com/paleopete/)

[This message has been edited by Paleo Pete (edited 10-16-2000).]

Thanks Pete. I tried swaping the simms before this problem. So I'm pretty sure the two that are in there now are the only two that will work together. I also know one simm has parity, it's got 9 chips. Your probably right. I was starting to convince myself with the last post of the same thing, but I had already started it so I might as well finish right. http://www.PCGuide.com/ubb/wink.gif

You must have been lurking around here waiting, I just posted the reply about 10 minutes ago...If you've already tested them, then it's probably incompatible memory.

I have several here that won't work with anything else, so I have a P-60 sitting here with only 24MB in it, when I have two 16MB chips sittint there I can't use. They won't work together, or with anything I put them with. Sure wish I had a couple of 16MB Parity chips, they would be in it right now! Parity is actually better memory than non-parity...and if I had two 16MB EDO chips, they'd be in this machine. Only have 32MB in it, and haven't been able to afford more. Sure sucks to have two sitting there and can't use them...

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If you had everything...Where would you put it?

Computer Information Links (http://www.geocities.com/paleopete/)

In addition to the suggestions that have been posted in recent history to identfying mobo's (BIOS strings, FCC numbers, etc.). There is a free profile program offered by www.belarc.com (http://www.belarc.com) that does a fairly good job of listing the hardware components and installed software. It also ID'd my mobo accurately. It is a small program. I have an AST Advantage 818 system P133MHZ and it listed the motherboard as an Intel Advanced/MA Code name Monaco. In addition to using the BIOS string (manually searching) either Award or AMI (I believe) has a small zip utility (freeware) with the primary function of identifying the BIOS data and date with a side function of identifying the mobo. They advise that it will not work on all systems, but...I have since lost the zip files. Nice to have as an IT tech/Help Desk Rep. Maybe save some time searching the web. http://www.PCGuide.com/ubb/cool.gif