5 messages in org.freebsd.freebsd-questionsRe: Is it possible to see memory over...| From | Sent On | Attachments |
|---|---|---|
| Yuri | Feb 17, 2010 11:53 am | |
| Bill Moran | Feb 17, 2010 12:01 pm | |
| Erik Trulsson | Feb 17, 2010 12:23 pm | |
| Yuri | Feb 17, 2010 3:59 pm | |
| Chuck Swiger | Feb 17, 2010 4:51 pm |
| Subject: | Re: Is it possible to see memory over 3GB on 32-bit FreeBSD? | |
|---|---|---|
| From: | Chuck Swiger (cswi...@mac.com) | |
| Date: | Feb 17, 2010 4:51:37 pm | |
| List: | org.freebsd.freebsd-questions | |
Hi--
On Feb 17, 2010, at 3:59 PM, Yuri wrote:
Erik Trulsson wrote:
It very much depends on what hardware you have in the system. Just
about every expansion card or I/O device will reserve some of the
address space for its own use. Some devices will need a lot of space - a
graphics card with 256MB of RAM on it will use (at least) 256MB of the address
space for example.
This doesn't seem like a good idea that video memory is always mapped to system
memory. What if one day graphics card gets 4GB RAM? Then we won't even be able
to have 32-bit OS working with such card and in 64-bit OS 4GB of memory would be
grossly wasted.
At one point, there was a considerable advantage to have video card memory fully
mapped into untranslated address space so that various things could read or
write as they pleased (cf "VESA linear framebuffer"); generally they gained
speed advantages from this.
With AGP's GART, the amount of memory available for textures, bump-maps, etc,
could reside in video card memory, local RAM, or a combination. Modern video
cards do not have keep their entire memory space mapped into address space; for
example, a nVidia 275 card with 1792 MB of RAM doesn't seem to want more than
256MB of address space under 32-bit Windows platforms.
Regards,
-- -Chuck
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