'johns' wrote, in part:
| I can only assume that
| the video card ram is not on the memory bus, but is treated
| like I/O .. and maybe even like a serial device. Otherwise,
| the video ram addressing would conflict with the system
| memory addressing. Main reason I think this, is the term
| "ram" doesn't make any sense for a video card. There is
| no need to "randomly" access the ram on a video card.
| That clearly makes it some kind of serial device .. like
| a UART ... that can be tri-stated and share its bus.
_____
I think you are confusing video ram, video display adapters, frame buffers,
and main memory.
#1. There IS a need for random access for memory on video display adapters,
this ram is used for several purposes, among which are
a. frame buffer (this seems to be the purpose you are thinking
of), the area that stores the image to be displayed; more than one exists
b. texture storage
c. program storage for programmable GPUs
#2. A frame buffer, even for very high resolution and large color depth
is not very large compared to the memory installed on video display adapters
or as main memory in a system; 8 MBytes for each buffer at a resolution of
1600 X 1200 X 32 bits. One buffer is used to refresh the display while
others are used to construct images.
#3. Video memory is a TYPE of ram; it is dual ported so that reads and
writes can be set up at the same time for any location
#4. Main memory space used by memory display adapters is mapped; it does
not need to be contiguous, nor does it need to be physical. This space is
used to transfer data back and forth on the AGP or PCI Express bus; it need
not be anything like the size of memory space on the video display adapter.
You can find out more by reading the AGP Bus and PCI Express Bus standards.
A good place to start for PCI Express Bus is at
http://zone.ni.com/devzone/cda/tut/p/id/3767 (the standards committee
charges for the complete specifications, and you might not want to pay the
$1500 the official specifications that PCI-SIG charges.)
For the AGP bus a good place to start is at
http://members.datafast.net.au/dft0802/specs.htm (also has information on
PCI Express.
Phil Weldon
|
| > I want to know how much I will get if I install more RAM or some
| > piece of hardware's effect in this respect.
|
| So do I. I called Gigabyte about this, and the tech said
| that Windows will only report unmapped ram .. therefore
| the 3 gig .. 3.3gig .. etc ... BUT .. he said that the system
| will still use your 4 gigs of ram. I can only assume that
| the video card ram is not on the memory bus, but is treated
| like I/O .. and maybe even like a serial device. Otherwise,
| the video ram addressing would conflict with the system
| memory addressing. Main reason I think this, is the term
| "ram" doesn't make any sense for a video card. There is
| no need to "randomly" access the ram on a video card.
| That clearly makes it some kind of serial device .. like
| a UART ... that can be tri-stated and share its bus. If
| there is some kind of random logic on a video card,
| it has its own internal bus for that, and so there is no
| system "memory addressing" going on. It would be
| nice to find out the facts one way or the other. I'm
| using 4 gigs of ram, and it makes a big difference in
| Vista and G3.
|
| johns
|