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PCI-E

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March 6, 2010 6:50:29 PM

I have a Gigabyte GA-P55A-UD3 mobo,
an intel i5-750 2.66GHz @ 3.6GHz,
4Gb DDR3 1600MHz RAM,
an ATi 4850 512Mb graphics card,
and an Asus D2X soundcard.

Now the motherboard has 2 pci-e 1x slots, 2 pci-e 16x slots, and 3 pci slots.

However, I know that with the release of the i5, they moved the pci-express controller for the 16x slots to the processor, which in theory means 2 graphics cards would run at 8x speed.

This is all very well for 2 graphics cards, but I only have 1...

My graphics card is in the main PCI-E 16x slot, but unfortunately the pci-e 1x slots are either side of this... the graphics card overheats if i have the soundcard in one of these, the ATi 4850 being a hot-running card.

I have the soundcard instead in the other 16x slot, which on my older system, an SLi AMD AM2 mobo simply slows the slot down to the 1x and runs it off the other controller. Is this the same for P55 mobos? or am I slowing down my graphics card by having it in this slot?

More about : pci

a b V Motherboard
March 6, 2010 10:33:13 PM

Dracio said:
However, I know that with the release of the i5, they moved the pci-express controller for the 16x slots to the processor, which in theory means 2 graphics cards would run at 8x speed.

This (2 graphics cards will run at x8,x8) is not true for all P55 motherboards. Most (all?) boards that this applies to are CF/SLI certified. Yours is not, that's the first indicator your primary slot won't be reduced to x8 if you insert a second card. In fact, if you read the specs for your board it states that the board has one PCIe x16 slot running at x16, and a second PCIe x16 slot running at x4.

The Lynnfield CPUs support 16 lanes directly connected to the CPU. All additional lanes run through the PCH. Those boards that have two 16 PCIe slots connected directly to the CPU will run one slot at x16 when only one card is inserted, or both slots at x8,x8 when two cards are inserted. But your board is not designed this way. Your second x16 slot always only runs at x4 because it runs through the PCH. So inserting another card in this second slot will not reduce the lanes dedicated to your GPU.

However, Gigabyte's implementation of USB 3.0/SATA3 can impact the primary GPU slot. When SATA3 / USB 3.0 (Marvell 9128 /NEC USB 3.0 Controllers) work at turbo mode, the 1st PCIE x16 will work at x8 speed.

http://www.gigabyte.us/Products/Motherboard/Products_Sp...
March 7, 2010 10:05:37 PM

Thanks for your answer :) 
It's a relief to know my soundcard isn't slowing down my graphics card!

however, It does say that my mobo supports crossfire, so if I were to run 2 graphics cards, how would that work? would it be one at x16 and one at x4?
a b V Motherboard
March 8, 2010 12:03:20 AM

Yes, your cards would run at x16, x4. Not really an ideal setup and I don't know how much benefit, if any, you'll get. However, I don't remember seeing any recent benchmarks for x16, x4. Nvidia wil not certify SLI to run on x16, x4 boards because of worries it will leave the consumer with a negative experience.
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