View Full Version : 8M Memory: 8192K or 7808K?

April 4th, 2009, 05:02 AM
Hello everyone, I have another problem with my 386 mobo (or it's simply my ignorance with memory management).

The first time I ran my 386, bios reported 8192K memory (and some CMOS charge and keyboard error). I have a photo of it, it was not a dream :p

After replacing cmos battery and fixed keyboard connector, I have not errors, but bios reports 7808K memory (384K difference). I tried to replace the eight banks of SIMM with other banks and I've the same problem. QNX floppy demo don't want to start so I need to have this 384K memory.

Is there something that I don't know about bios settings?

Thank you in advance as usual :)

See you!

April 4th, 2009, 05:55 AM
Look up 'Shadow Memory'.

An x86 machine with more than 640K generally is missing 384K of that memory. That's because the memory that exists between 640K and 1024K is reserved for ROM and expansion cards.

Most machines will give you the option to use pieces of that that memory as RAM ('high memory for DOS device drivers') or as copies of the slower ROM chips, but some of it will not be able to be recovered. Video memory falls into this category - your video card provides memory, and some of the memory on the motherboard is at the same exact address. Your video card has to 'win' that conflict, otherwise nothing would work. The same goes for any add-in cards that provide BIOS extensions.

What would really be nice is if the motherboard chipsets could just leave a hole between 640K and 1024K (as originally architected) and push the extra 384K up higher so that you would have a full 8192K of RAM available. That kind of circuitry is expensive and RAM was getting cheaper at that time, so it generally wasn't built like that.

April 4th, 2009, 07:02 AM
Hello Mbbrutman, thank you for prompt reply...

I remember something about 384k memory hole or something into bios, tonight I will check bios and make some photo to check together if some option may solve this problem.

See you soon!

April 4th, 2009, 09:17 AM
Here is a screen photo of the bios, I tried to change "384KB Memory Relocation" from Disabled to Enabled but I have the same problem


April 4th, 2009, 09:20 AM
Here is the photo with "8192"... Same SIMM banks, same VGA, same HD controller, keyboard not running and CMOS not charged :eek: :eek:


April 6th, 2009, 03:41 AM
I made some experiment last night, I cleared CMOS and at the first boot the amount of memory is 8192 k of ram, BIOS reports: "Cmos display tipe mismatch" and "Press <F1> to continue". So I enter bios and save to cmos without changing anything: in the next boot BIOS report 7808 k of ram.

Any idea on how to recover some byte? QNX floppy demo requires at least 8000K to run...


April 7th, 2009, 03:23 AM
When you set '384 KB Memory Relocation' to 'Enabled', did that automatically disable all 10 of the 'ROM shadow' options?
If not, what might be happening is that even though you set '384 KB Memory Relocation' to 'Enabled', maybe the BIOS is ignoring that because one of more of the 10 'ROM shadow' options enabled.

April 8th, 2009, 01:38 PM
Thank you for your reply, yes, it's true, if I set it on Enabled, it switch on Disabled automatically, tomorrow I'll try to disable any ROM SHADOW option and enable 384K relocation.

See you tomorrow! :D

April 9th, 2009, 02:48 AM
This is the second question and the second solving for this problem, THANKS to EVERYONE in this great forum, now I have 8192kb free and QNX starts correctly!

See you!