GA-P55A-UD4 - PCI-E X8 slot for graphics

[early]

I'm looking at this motherboard.

Since the placement of the first PCI-E (X16) slot is rather inconvenient, I was thinking of using the second one (X8) for my only graphics card.

1. Would this work?

2. Would the PCI-E speed of this slot get reduced any further if I turn on the USB 3 or SATA 6G "boost"? (I know the speed gets reduced for the first slot.)

[wazza300]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

i think your fine its only in sli/crossfire that both lanes get reduced to 8x-8x when sata3/usb3 are enabled

[Chike]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

I haven't seen anything about reducing PCI-E speed, only that SATA 6 and USB 3 are not possble with 2 graphic cards.

[wazza300]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

heres what i managed to find on the net

From the manual of GA-P55A-UD3P, it is stated that when the Turbo SATA3 or USB 3.0 is enabled, the PCIe graphics slot will drop from PCIe x16 to PCIe x8.
You would have to choose if you want maximum graphics performance or maximum disk performance. These new boards uses the NEC 3.0 chip and SATA 3 which requires more bandwidth than just PCIe x1. As the P55 and CPU does not have enough lanes to support, the PCIe x16 is reduced to PCIe x8.
Although PCIe x8 won’t give you much of a performance dip, it gives you maximum USB3.0 performance at the expense of the 8 lane instead of 16. Now the issue is, if we still want Turbo SATA3 and USB 3.0 and want SLI or CrossFire with 2 cards. Will the two PCIe slots be running at Dual 4x (4x + 4x) ? Do let us know if you own the P55 series of boards with NEC USB 3.0 on board.
Gigabyte has replied to us
First of all, if users really want to use CrossFire / SLI on a P55 motherboards, as you know the PCI-e x16 lanes will split into 2 x8 lanes, besides that users are still able to enjoy the benefits of USB 3.0 and SATA 6G.
It is only when user is using one graphics card, then the user is able to select whether he wants to use the full bandwidth of USB 3.0 or SATA 6G. Of course, according to our manual had clearly stated the PCI-e graphics will operate in x8 mode. But the true fact is, there’s no identical performance drop comparing with a PCI-e x16 to a PCI-e x8 graphics.
Plus, our implementation gives users a more flexible choice and paying less money to enjoy USB 3.0 / SATA 6G.
When CF/SLI is running in dual 8X, the SATA3 and USB3 will be running in non turbo mode, getting the PCie lane from the P55 chipset instead of from the CPU, thus allowing the CF/SLI to run in Dual 8x mode.

[Mae]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

I got another question regading that topic.

I want to use one graphics card in the 16x and also at 16x speed, so i have to set the Turbo SATA3/USB3 in BIOS to "disabled".
At which speed will the Marvell 9128 chip operate 2 SATA 3Gb/s HDDs in RAID 0 settings if set the option mentioned above (e.g. turbomode disabled)? Will i cap out on bandwith? The HDD's i want to use are WD RE3 500 GB SATA Festplatten ( WD5002ABYS )

[wazza300]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

it doesnt affect anything if your only using one gpu,it reduces bandwidth when you use two or more gpu's

[Mae]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

So technically i am able to use 1 GPU at 16x PEG and the Turbomode on SATA 6gb/s witout any kind of performance loss?

Awesome, thanks :)

[wazza300]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

i thinkso,doesnt it tell you in your mb manual? ill do some searching just to make sure

[Psycho101]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

As it clearly states in the extracts you posted, if USB or SATA3 full speed modes are enabled, any single GPU in the system will be cut down to 8 lanes. Yes, you need to disable any turbo modes to run 16x. However, why would you want to run 16 lanes of bandwidth with a single GPU card? It makes zero difference if running 16x compared to 8x.

Also as clearly stated in those quotes from Gigabyte, if running a crossfire setup or SLI setup the turbo and high speed modes of USB3 and SATA3 are disables and locked out. The options will appear in gray in the BIOS and can not be changed.

[Mae]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

Because some testing discovered that there ARE performance issues at high resolutions and AA/AS.
Maybe engine-dependent. I just wanted to make sure i read the documentation right. Thanks for your comments.

Edit: Post some decent information that proofes me wrong. People are telling me both things and i just favor a good graphical performance over a fast usb-connector.

[Psycho101]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

No, there are no "issues" with a single card running at 8x. There is no single GPU on the plannet that can saturate an 8x bus, no where near.

Even running two 480's in crossfire on dual 8x links only encountered very slight performance drops when running spanned resolutions, ie 2 or more 1920x1200 monitors. Same goes for the HD 5800 series, with the only drop noticed being when running 3 monitor eyefinity setups.

So why does a single GPU have zero issues when running 8x, yet dual 8x crossfire/sli does take a miniscule performance drop? Because information is not only passed card to card by the crossfire/SLI bridge, but also over the PCIe bus, using a small portion of available bandwidth.

There really is no need to post any proof as to be honest, I don't trust most sites to be able to conduct tests fairly, or to know the difference between natural variation and a true result. However, we can use our own logic to "prove" in a way that 8 lanes for a single GPU is fine. Two words.. "Dual GPU" Graphics Cards. If you truely believe what you may have read, that 8x isn't enough for a single GPU card, then surely 16x isn't enough for a dual GPU card. By that same logic, every single dual GPU card (recent examples include GTX 295, HD4870X2, HD5890) is being cripples by "only" having 16 lanes of bandwidth. This is obviously not true. If it were, then all dual GPU cards would basically be inferior products because of it. They are not. A Dual GPU card on a 16x connection is identical in performance to two single GPU cards in SLI/Crossfire as long as clock speeds are the same. Enthusiasts simply would not tolerate there being any discrepancy and would chose the two single card option every time.

The only exception to there being no difference between 8x and 16x is when using dual GPU cards. There most certainly is a difference when running a dual GPU card on a 8x connection. Not as much as you'd think, but it's enough to make you not want to run Quad SLI or CrossfireX on a 8x/8x only capable board.

There will be many others here who could confirm this, but in summary, as a modern single GPU card doesn't even eat 7 lanes of bandwidth, let alone 8x, there is zero difference running 16x or 8x.

I would be happy to demonstrate this by running a few benchmarks. As you can see from my sig, I can run them with a card pulled for 16x and then with USB/SATA3 kicked up to full.

Edit: link to the 480 8x/8x vs 16x/16x tests: Introduction - GTX 480 SLI @ 2560x1600 - GTX 480 SLI PCIe Bandwidth Perf. - x16/x16 vs. x8/x8 | [H]ard|OCP

[wazza300]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

yes thats right,i didnt read through what i posted earlier,so one gpu lets u use full sata3 and usb3 inc turbo but at 8x for gpu ,or 16x if you disable turbo

crossfire will both be 8x and you can still use sata3 and usb3 but without turbo

maybe the newer p67 mb's will eliminate all this and be like the ex58's sata3/usb3

it still wont affect performance

[Psycho101]

Re: GA-P55A-UD4 - PCI-E X8 slot for graphics

I hope so too. Doesn't seem fair having to sometimes compromise if you want to run CF/SLI on a mid end solution. It's also a possibility that USB3 and SATA3 will be supported natively by P67. i had heard that initially Intel wanted to use Light-Peek and drop USB3, but I think they've seen reason and changed their minds.

Yes, the only no no at the moment is Quad SLI or 4-Way Crossfire on a mid range i7/i5/i3, and to be honest, if a person has the money for two 5890's then they're going to be using X58 any way.

I guess that's the issue with so many enthusiast publications around on the net. it's very easy to read articles and decide you need "x" when really it makes no difference at that person's chosen resolution, is too cost ineffective or worst of all, doesn't provide a tangable benefit, eg making a previously unplayable game (<25-30 FPS) playable.

Also worth noting and relevant to the OP's questions, is the fact that SATA3 offers virtually zero performance gain when using a mechanical (spinning platter) HDD. The industry is slightly to blame again for touting the old "Faster=Better" slogan. As even a 600GB WD Raptor can't come anywhere near saturating a SATA2 connection, let alone SATA3, the only figures that benefit are Drive Controler to Interface (SATA Port) and Burst rate. This is to be expected of course, as there needs to be radical improvements to disk density and recording techniques before any mechanical mainstream drive will crack 300MB/s (SATA2) let alone SATA3.