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-   -   Hey Sky, heads up about x8/x8 CF. (https://www.hardwarecanucks.com/forum/video-cards/8045-hey-sky-heads-up-about-x8-x8-cf.html)

S_G June 19, 2008 12:43 PM

Hey Sky, heads up about x8/x8 CF.
 
Intel P45 Vs. X48 Crossfire Performance :: TweakTown

Looks like x8/x8 is causing some trouble for the 4850s in CrossFire.

Cheator June 19, 2008 12:46 PM

Hmm.. yeah..Just picked up a P5Q-E. Ah well, its certainly more performance than I have now.

SKYMTL June 19, 2008 12:49 PM

Until I see a site other than Tweaktown testing this, I will reserve my judgement. Period.

S_G June 19, 2008 12:52 PM

Bit-Tech also did one a while back, comparing P35 to X38:

bit-tech.net | Review - CrossFire Comparison: Intel X38 vs. P35


For them, only Quake Wars was really affected. Everything else was fairly random or within a margin or error.

Eldonko June 19, 2008 01:05 PM

Very interesting, thanks for posting. I was thinking the latest gen GPUs would make more use of the bandwidth. Obviously the newer the GPU and driver the bigger difference there will be. Im thinking if I tested the same thing on 3870 it would not be quite the same conclusion as they posted:

Quote:

If you’re really thinking about going down the Crossfire path, we would be highly recommending that you spend the extra money to go to an X38 or X48 based motherboard over the P45.

SKYMTL June 19, 2008 01:08 PM

Maybe I should put some information behind why I have an issue with this article. I am not calling it BS...I just want to furnish you guys with some info.

Please remember in all of this that P45 boards have TWO 8X PCI-E 2.0 slots when working in Crossfire.

PCI-E 1.1 transfers 250MB/s in each direction (up / down) per lane.
This means that at 8x (8 lanes) would be transfering 2GB/s and 16x would be transfering 4GB/s

With me? I hope so!!

PCI-E 2.0 was instituted and DOUBLED that rate to 500 MB/s in each direction per lane
That means that 8x transfers 4GB/s and 16x goes for a whooping 8GB/s

Still here? Good!!!

To put this into context, check this out:

PCI-E 1.1:
8x = 2GB/s
16x = 4GB/s

PCI-E 2.0:
8x = 4GB/s
16x = 8GB/s

Now let's come out with it shall we?

PCI-E 2.0 8x = 4GB/s
PCI-E 1.1 16x = 4GB/s


Wee what I'm saying?

Basically they are saying that a PCI-E 1.1 16x slot will bottleneck a HD4850 card.

ebdoradz June 19, 2008 01:18 PM

the question is does it really bottleneck a 4850 card?

SKYMTL June 19, 2008 01:22 PM

I just don't see how especially if MUCH more powerful cards are not.

Put it this way: if rumors are correct and the R700 is basically made up of TWO HD4870 cores (which are more powerful than the one on the HD4850), that card would be bottlenecked by a PCI-E 2.0 16x interface. I think not.

'Nuff said.

ebdoradz June 19, 2008 01:42 PM

Quote:

Originally Posted by SKYMTL (Post 63021)
I just don't see how especially if MUCH more powerful cards are not.

Put it this way: if rumors are correct and the R700 is basically made up of TWO HD4870 cores (which are more powerful than the one on the HD4850), that card would be bottlenecked by a PCI-E 2.0 16x interface. I think not.

'Nuff said.

Now if i wanna upgrade my ""Yellow"" rig to a 4850 does it worth it???

i mean does my 2.8Ghz opty will bottleneck thevideo card, or i should upgrade to a new platform (intel or am2+)????

Eldonko June 19, 2008 03:17 PM

Good explanation SKYMTL


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