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PCIe 16x V.S. PCIe 8x - Does it matter?

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  • Asus
  • Chipsets
  • Motherboards
Last response: in Motherboards
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June 14, 2011 11:15:59 PM

Im doing a major upgrade on my gaming computer around the core i7 2600k with a P67 chipset witch is the most powerful combonation you can get with the 2600k, however the P67 chipset doesn't support multiple PCIe slots and since im putting in multiple graphics cards this is a problem. most companies try to solve this single PCIe problem by spitting up the bus lanes so when you put in more cards your bandwith is split in half with each new card. My question then is this, with 2 Evga GTX 570's superclocked to 797mhz , should i ither spend more money on on the Asus WS Revolution with the NF200 chipset witch alows me to have 2 cards with PCIe 16x or should i get a mobo within the range of motherboards that as i described turns your PCI 16x into an 8x and so on.

NOTE:
Evga P67FTW mobo: includes Evga E-leet tune up witch works particularly well with there graphics cards

Asus P8P67 deluxe mobo: includes blue tooth and comes with a better warranty


In short will a Evga GTX 570 at 797mhz ever need more bandwidth than a PCIe 8x can provide.

More about : pcie 16x pcie matter

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a b V Motherboard
June 15, 2011 1:54:06 AM

Tom's did a study on this just last year, Here is the link. A quick quote:

Quote:
A motherboard doesn't always come with two fully-featured PCI Express x16 slots. Available PCI Express lanes are often distributed across two slots, meaning that the second PCIe port may only run eight lanes electrically. This also means that the speed of one physical x16 PCIe port decreases when you use expand out to a second slot. If you're running a P55-based platform, like our test system, this applies to you.

But don't worry yet. Our tests show that even with the fast Radeon HD 5870 and Radeon HD 5850 cards, the performance impact when switching from PCI Express x16 to x8 is only a few frames per second (remember to check out next week's coverage for more in-depth exploration of PCI Express scaling). Additionally, both cards are throttled at x8, even if you combine a x16 and a x8 slot. According to the GPU-Z tool, the CrossFire configuration is completely synchronized.


And another quote:

Quote:
With Nvidia, you have a bit more flexibility in slot selection. Even the fastest graphics cards are recognized as an SLI configuration, even if you don't use the SLI bridge connector and instead let the PCIe interface handle all data transfers. However, this comes at the expense of some performance. Ideally, you should always use a bridge connector to link the two cards together. Interestingly, GPU-Z shows that when you combine Nvidia cards in x16 and x8 slots, each card in the SLI configuration still runs at the speed of its respective slot.

With a bridge connector, the difference in speed is within the measuring tolerance. Without a bridge connector, though, you can clearly see that the cards use different interface speeds, and you witness a performance hit of up to 13% in SLI mode.


As you can see, not much difference in performance at all. PCIe 8x is still wicked fast...
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June 15, 2011 1:37:59 PM

thanks by the way, also i had another question about motherboards someone told me that that when you use ati vs nvidia with an Intel chipset and CPU you are actually getting less bandwidth. he made this inference based on the fact that you usually can have more crossfire than sli. is this true?
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June 22, 2011 2:47:36 AM

Best answer selected by youngblood1017.
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