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September 16th 07, 02:41 AM
The Nvidia GX2 series that uses two cards... do they both use the
card's combined memory? Ex. 8850gx2 = 640*2 and all of that memory is
available to applications / games combined? The same with the
pipelines?

I know SLI doesn't combine memory, so that's why I'm asking. I don't
know the difference between these two approaches.

Thanks!

First of One[_2_]
September 16th 07, 05:04 AM
The 7950GX2 was implemented through SLI, with all the quirks and limitations
therein, except it didn't require the motherboard to have an SLI chipset.

Googling for 8850GX2 turned up this article from April:
http://xtreview.com/addcomment-id-2108-view-GeForce-8950GX2-to-be-renamed-in-8850GX2.html

Obviously it never happened. A 8850GX2 was probably deemed unnecessary
(2900XT slower than expected) or impractical (heat, power). Recall the 7900
chip had a small die and was exceptionally cool-running.

--
"War is the continuation of politics by other means.
It can therefore be said that politics is war without
bloodshed while war is politics with bloodshed."

> wrote in message
oups.com...
> The Nvidia GX2 series that uses two cards... do they both use the
> card's combined memory? Ex. 8850gx2 = 640*2 and all of that memory is
> available to applications / games combined? The same with the
> pipelines?
>
> I know SLI doesn't combine memory, so that's why I'm asking. I don't
> know the difference between these two approaches.
>
> Thanks!
>

Augustus
September 16th 07, 05:05 AM
> wrote in message
oups.com...
> The Nvidia GX2 series that uses two cards... do they both use the
> card's combined memory? Ex. 8850gx2 = 640*2 and all of that memory is
> available to applications / games combined? The same with the
> pipelines?
>
> I know SLI doesn't combine memory, so that's why I'm asking. I don't
> know the difference between these two approaches.

They don't combine the memory.....it acts like two cards with discrete
memory and shaders/pipelines , basically SLI in a one card solution. Like
the 7950 card. The 8850 GX2 is basically 2 warmed up 8800GTS 640Mb cards
spliced onto the same card. Supposed to be 75% faster than a 768Mb 8800GTX.
http://xtreview.com/addcomment-id-2108-view-GeForce-8950GX2-to-be-renamed-in-8850GX2.html

Paul
September 16th 07, 05:13 AM
wrote:
> The Nvidia GX2 series that uses two cards... do they both use the
> card's combined memory? Ex. 8850gx2 = 640*2 and all of that memory is
> available to applications / games combined? The same with the
> pipelines?
>
> I know SLI doesn't combine memory, so that's why I'm asking. I don't
> know the difference between these two approaches.
>
> Thanks!
>

http://www.xbitlabs.com/images/video/nvidia-gf7950gx2/gf7950gx2_board_assemble_bg.jpg

A two card video card, looks like this. In the above picture, card #1
is the bottom card, and card #2 is the top card.

<-- Card #2 --> | <------- Card #1 ------->
|
GPU | GPU
| | |
+---------- PCI_Express ----------+
X16 | Switch Chip x16
| |
| |
x16 Bus Connector

The two card set is SLI, and the designer could use a
link between GPUs, or the other technique is to send
packets across the PCI Express bus to do the same thing.

The purpose of the switch chip, is so that the PCI Express
wiring is available to both GPUs. That way, the module only
takes up one PCI Express slot on the motherboard (which makes
it easier to plug in the module at install time).

The implication is, that it will behave just like a pair
of cards in SLI.

For 7950GX2, the listing here says each GPU has 512MB, but the
overall module will make 512MB available to the system (so the
memories don't add).

http://www.xbitlabs.com/articles/video/display/nvidia-gf7950gx2_3.html

And this page warns that not all motherboard BIOS, understand how to
traverse a PCI Express switch chip. I expect this is similar to the
problem of motherboards in the past, not all handling PCI bridge chips
properly.

http://www.xbitlabs.com/articles/video/display/nvidia-gf7950gx2_2.html

If you stick two 8800GTX together in a module, the heat output would
be a serious issue. The resulting module could be quite thick (to allow
for air cooling and heatsink fins etc), or have an exotic cooling
solution like water cooling.

Paul