Messages in this thread |  | | | Date | Wed, 10 Apr 2002 11:53:15 -0400 (EDT) | | From | Byron Stanoszek <> | | Subject | RE: Using video memory as system memory |
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On Wed, 10 Apr 2002, Holzrichter, Bruce wrote:
> I thought that this was interesting as well, and had a couple of questions, > as I am no expert in this stuff. > > You don't have the frame buffer enabled for display when trying to use this > as system memory, correct?
Correct. :) In fact, text mode can only take a maximum of the first 256KB of memory of the card (extended text paging). So as long as you only target the rest of the memory (and don't use X or svgalib) you should be fine.
> Are there implications of the BIOS shadowing video memory to system memory, > or is that not an issue once Linux takes over memory control?
Not that I'm aware of. This is PCI-mapped prefetchable memory.
> That is a neat idea, though. The PCI/AGP bus may be a limiting factor for > this as well, correct? As far as speed, I believe most video cards have > fast memory, vram, or sram, but it's only useful transferring between the > Video GPU, and Video cards memory, as the bus to the video card is the > bottleneck.
Yeah. In fact in some responses the 'slow speed' consideration was so much that they all say I'd be better off writing a block driver and making use of the memory more as a swap device rather than as system RAM.
Has anyone out there done this yet? I figure I'd ask before reinventing anything.. :)
-Byron
-- Byron Stanoszek Ph: (330) 644-3059 Systems Programmer Fax: (330) 644-8110 Commercial Timesharing Inc. Email: byron@comtime.com
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