Hacking Linux to reduce VRAM

[sam tygier]

On 04/01/11 11:15, Chris Angelico wrote:
> Hi! I'm relatively new to Ubuntu, having only seriously used it for a
> few months, but I've used various POSIX-compliant systems for a number
> of years. Got a bit of a weird problem, possibly not something
> anyone's ever needed to do, but hopefully it'll be of interest to
> someone!
>
> My question is this: Can the kernel or driver be hacked to reduce the
> announced amount of VRAM?
>
> I have an Acer eMachines EL1300 computer which I'm using as a disk
> server (Samba and FTP), and as a scratch box for my Wine experiments
> (suspicious Windows software does NOT belong on a Windows computer).
> There appears to be a fault in the mainboard which results in errors
> in video RAM; it uses an onboard nvidia GPU and shared video memory,
> configurable between 32MB and 256MB. Most of the time, the system
> works flawlessly, but occasionally (seems to coincide with heavy
> graphics usage) it freezes dead; this is confirmed by the Video Memory
> Stress Test tool. Changing DIMM didn't change this; the same addresses
> showed faulty. Adding a dedicated video card doesn't seem to be an
> option on this uber-cheap mainboard.
>
> Currently, the BIOS is set to give 256MB to video, out of 3GB total
> installed memory. I'd like to tell the application that there's only
> 255MB (or even 256MB-64KB) of video memory, which would neatly prevent
> it from accessing the failing addresses, which are 0FFF3480-0FFF3483
> within video memory. Is this possible?
>
> Chris Angelico
>

have you tried using badram or memmap?
http://rick.vanrein.org/linux/badram/index.html
https://help.ubuntu.com/community/BadRAM
http://gquigs.blogspot.com/2009/01/bad-memory-howto.html

sam