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Performance difference: P45 vs X48 on Crossfire x8 vs x16

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September 14, 2008 2:58:13 PM

ASUS's P45 boards only yield x8 on its PCIe 2.0 x16 slot while X48 chipset can deliver full throughput.

Does anyone know the actual difference, is it noticable, or what kind of program would be affected the most?

thanks in advance.
a b V Motherboard
September 14, 2008 3:11:07 PM

P45 runs one card at x16, but in crossfire (2 cards) runs at x8.

The difference is around 4 FPS in most games, with 2 4850s at a resolution of 1680x1050. As you increase the resolution from there, performance gradually deteriorates... maybe 10-12 FPS at very high resolutions.
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a b V Motherboard
September 14, 2008 3:31:59 PM

That is the best comparison. :) 

Just be sure to look at the actual numbers. Like all these sites, they want their charts to look dramatic and so they tend to exaggerate the distance between the bars on the charts.

The best thing I can tell you is, P45 is great for a single card or if you want to buy one card now, but keep your options open for a second one later, maybe.

If you are buying two cards right away and you want to crossfire for a monitor larger than 22" then you likely need an x48.
September 14, 2008 3:32:48 PM

I think it is unlikely I would use two cards at the same time. I am not a gamer, the FPS difference to me is somewhat magical.

Thanks for the info!
September 14, 2008 3:43:31 PM

jjyu2000 said:
I think it is unlikely I would use two cards at the same time. I am not a gamer, the FPS difference to me is somewhat magical.

Thanks for the info!


Keep in mind, the Legionhardware benchmarks can be a little misleading. For example, in their Crysis test, it's run in DX9, with both AA and AF off.
http://www.legionhardware.com/document.php?id=761&p=2
Here's another bench using max settings, DX10, AA+AF.
http://www.tweaktown.com/articles/1472/7/page_7_benchma...

As you can see, the difference is much bigger. At the lower settings, the load isn't heavy enough for significant bottlenecking to occur.
September 14, 2008 3:50:53 PM

Good Observation Dagger.

I saw both reviews and was curious about the different results with the x4850, but did not have time to try and analyze the difference.


!