Hacking Linux to reduce VRAM

[Chris Angelico]

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