OS won't load - "HIMEM.SYS has detected unreliable XMS memory ..."

This began by the computer all of a sudden re-booting on it's own when I was in the middle of a program or game. The screen would just go black, I would see the "no signal" message from the monitor followed by a re-boot, Scan Disk, etc. This occurred about a dozen times over 5-6 days.

Today I can't even get the computer to load the OS. When I turn it on, Win98 begins to load until it gets to the point of displaying "HIMEM is testing extended memory" - then, after a few seconds it displays an error message about unreliable XMS memory at address 0382B278 (although the number and exact test changes from time to time).

I have a 1G AMD with 512 MB RAM running Win98SE. I have tried - without success - the following:
1. Using different sticks of RAM, one at a time.
2. Replacing the AGP graphics card.
3. Booting without any PCI cards.
4. Pulled out secondary IDE cable.
5. Switched IDE cables.
6. Removed/replaced CMOS battery.
7. Checked every connection on motherboard, including removing/replacing the CPU.
8. Using 4 different (backup) hard drives - all of which I know were working fine, but now all of them produce the same result.

So, hardware problem? Motherboard?

Any suggestions or assistance will be greatly appreciated.

Perhaps the FSB is set too high, or the power supply is weakening and can't provide steady power to RAM, or some other problem with voltage regulation.

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CPU: Am386DX-40
FPU: Cx387DX-40
RAM: 32MB, 128KB Cache
HDD's: (2) 540MB
CDROM: GCD-R580B (8x)
VIDEO: 2MB Trident
SOUND: SB16 PnP
NIC: 3Com 3c509
OS: DR-DOS 7.04, Win3.11 w/ Win32s

AlaricD -

Thanks for the reply.
Sorry, what is the FSB and how is it changed, please?

John

The Front-Side Bus is basically the speed at which the RAM runs. The easiest way to overclock is to crank up the FSB. It is done in the BIOS.

If the FSB is correctly clocked,
underclock it to see if the problem goes away. If so, it may point to a power supply problem, or just bad clock control on the motherboard.

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CPU: Am386DX-40
FPU: Cx387DX-40
RAM: 32MB, 128KB Cache
HDD's: (2) 540MB
CDROM: GCD-R580B (8x)
VIDEO: 2MB Trident
SOUND: SB16 PnP
NIC: 3Com 3c509
OS: DR-DOS 7.04, Win3.11 w/ Win32s

the system was never overclocked and I tried to underclock it but my BIOS evidently doesn'tgive me that option - only overclocking.

The power supply reads fine both with a voltmeter and from the BIOS "health status" screen.

I set it to load fail-safe defaults and it wouldn't even get to the boot menu. I then set it to load optimized defaults and I'm back to the "unreliable XMS memory" message - this time at address 001000D8.

The motherboard is a K7T Pro-2-A (MS-6330). Does it have to be replaced if it has a bad clock control ?

Try this MSKB document
http://support.microsoft.com/default...;EN-US;q109845

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Jerry CTX
Computer (In)Security
Fight UCITA

Thanks, Jerry - trying their suggestions now.

Well, everything seems to point to a bad "cache controller" (whatever that is). I imagine it's a built-in component of the motherboard, and not easily "fixable."

I've never replaced a motherboard but it may be time to experience it. https://discussions.virtualdr.com/

[This message has been edited by john.s (edited 05-12-2002).]

Until you replace the motherboard you could just disable the L2 cache in the BIOS-- but that will cause quite a performance hit. (But not as bad a performance hit as not even being able to boot to Windows!)

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CPU: Am386DX-40
FPU: Cx387DX-40
RAM: 32MB, 128KB Cache
HDD's: (2) 540MB
CDROM: GCD-R580B (8x)
VIDEO: 2MB Trident
SOUND: SB16 PnP
NIC: 3Com 3c509
OS: DR-DOS 7.04, Win3.11 w/ Win32s

If I disable the L2 cache in the BIOS the computer won't get past checking for the boot device ... it just looks for a floppy, then the CD-ROM, and hangs up before ever getting to the hard drive.

Oh well, ain't it fun!