Asus 4870 X2

THERESONATOR

Member
Jan 2, 2008
161
0
0
Hi

I like to buy the best of the best of the best when I buy a computer (within reason), which is why I want to shell out and buy a Asus 4870X2 for the Rampage Extreme II w/ the Core i7 920 I'm gonna get. I believe this motherboard features PCI Ex lane output for Crossfire of 16x/16x/8x. Which I would be fine with if I was buying just ordinary single GPU solutions. But seeing as there are two GPUs on each of these 4870X2's I buy, I am left wondering: does having one 4870X2 on a single slot reduce its output to each GPU to 8x?

The net effect of that scenario is of course me buying two 4870X2's only to find that I would've got the exact same output if I bought instead two single GPU 4870's. In terms of numbers I would be getting 8x/8x/8x/8x - but on two PCI Express slots. Its kinda like that for my current setup.

I only managed to get SLI last month on my 2 year old computer (DFI Skt 939 SLI-DR Expert w/ two BFG 7800GTXs) only to find that the board only supported an output of 8x/8x for both, net effect = same as having one card on a single x16 slot. I was really pi$$ed off with that. OK so it only cost me £40 (and far too much time to find a EXACT same card that is now way after-market and discontinued so that it would be compatible.. thanks eBay) but I don't want to go through that kind of pain again! So I'm doing my homework here.

What else really got my back up was when I bought Vista 64 the other day, only to find that it doesn't support my DX9 SLI cards! GRR!

OK so back to the question.

I want quad Crossfire with 16x to each GPU. Would I be able to get that with two 4870X2's in a Asus Rampage Extreme II, or is this not yet supported on any motherboard to date?

TIA.
 

masteryoda34

Golden Member
Dec 17, 2007
1,399
3
81
The bandwidth difference between 16x and 8x on PCI-E 2.0 makes no difference in real world applications. And secondly, the 4870 X2 uses an internal bridge chip for the PCI-E connection. See the chip between the two GPU's on this picture 4870 X2 PCB

So your question doesn't really have an answer and furthermore, it is irrelavent.
 

betasub

Platinum Member
Mar 22, 2006
2,677
0
0
Originally posted by: THERESONATOR
I only managed to get SLI last month on my 2 year old computer (DFI Skt 939 SLI-DR Expert w/ two BFG 7800GTXs) only to find that the board only supported an output of 8x/8x for both, net effect = same as having one card on a single x16 slot. I was really pi$$ed off with that. OK so it only cost me £40 (and far too much time to find a EXACT same card that is now way after-market and discontinued so that it would be compatible.. thanks eBay) but I don't want to go through that kind of pain again! So I'm doing my homework here.
You really think PCIe lane bandwidth was limiting your 7800GTX SLI? Even for PCIe v1 @8x, there's far more bandwidth than the 7800GTX would ever need. (With faster cards, FSX can provide an exception).

As for your single 4870X2 question, masteryoda is correct that inter-GPU traffic is handled over an internal bridge (AFAIK ATI haven't implemented the sideport yet). GPU-system communication is over the motherboard's PCIe2 @16x.

The quadfire question depends entirely on how Asus have configured the PCIe2 lanes on the Rampage II Extreme. Because it has the X58 chipset with 36 PCIe2 lanes, 16/16/8x isn't going to happen: 16/16/disabled? for dual cards, 16/8/8 for triple set-ups. For more on X58 and the Asus Rampage II Extreme, see Anand's motherboard reviews, such as here.
 

ASK THE COMMUNITY