Video Memory

Ray Parrish crp at
Mon Mar 2 23:15:27 UTC 2009

NoOp wrote:
> On 03/02/2009 03:38 AM, Ray Parrish wrote:
>> So... I'm not too sure what this is saying, as I do not know what the 
>> memory ranges are specifying for sure. The second memory range matches 
>> the reported 256 MB's reported by most utilities in Ubuntu, and dividing 
>> the last memory range by 1024 only once matches 128 MB's but that 
>> decimal number before division is only 131070.999658496 so if it's in 
>> bytes it doesn't make sense to only divide once.
>> Anybody out there write device drivers for video cards?
>> I guess I'll just have to continue to be mystified as to how much memory 
>> my card is actually using.
>> Later, Ray Parrish
> My _guess_ would be that your card is using shared memory and with your
> 512MB of ram it's 'Total Effective Memory' is 256MB. See:
> <*&p_li=&p_topview=1>
> You might find these of interest:
> [Memory management for graphics processors]
> Also, to get an idea of what each of your processes are using in the way
> of memory you can use pmap. You'll find this interesting:
> $ pmap `pidof compiz.real`
> and
> $ pmap `pidof compiz.real` -d |more
> See:
> and 'man pmap'
Yes! I did find that interesting reading. The Nvidia page specified the 
6200 series cards where mine is a 6100 series, but I suppose the same 
could apply to them as well. I tried to use the search on that page to 
discover any more articles of that nature, and it couldn't even find the 
article I was reading. How in the world did you find it?

I ran the two pmap commands, and the second one returned the highest 
amount, which when divided by 1024 to get MB's revealed a total of 63.5 
MB's in use. The other returned 61 MB's.

I was just in Windows, and it's System Information program reported 128 
MB's of video RAM. When I rebooted I decided to try an experiment, and 
went into the BIOS, and changed the video RAM setting to 64 MB's. After 
logging into Ubuntu, I find it still claims 256 MB's via SysInfo, and 
the Nvidia X Server Settings GUI application.

Likewise the "nvidia-settings --query all" command returns a value of 
256 MB's.

Having changed the video RAM setting in the BIOS seems to have had no 
effect on the performance of Ubuntu. I do not that free now reports a 
total of 438 MB's of system RAM, which differs from it's previous 
reports of 384 MB's with the previous BIOS setting of 128 MB's for the 
video RAM.

I have yet to read the pmap man page, and ran those commands without 
looking them up first. I trusted you that time, NoOp, but don't count on 
it in the future. 8-) I usually look up commands I find here first to 
make sure they're OK.

So... I guess it's possible that Ubuntu is allowing me to access VRAM 
that exists on the onboard card that Windows apparently doesn't know 
about. Very odd.

Thanks for the help!

Later, Ray Parrish

Human reviewed index of links about the computer
Poetry from the mind of a Schizophrenic

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