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What is this "P55 Chipset PCI-E 2.0 16x limitation" ?

Justin

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What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« on: July 04, 2010, 09:43:01 pm »
Hi all,

I've been thinking about getting a  GA-P55A-UD3 motherboard to replace my ageing AM2 mobo for quite some time now, but I've read that there's some kind of "PCI-E 2.0 16x limit"? Specifically, a user said that if one graphics card is installed and SATA 3 and USB 3 devices are in use, then the graphics card is forced to run at 8x. Why is this? Why can't both run at 16x?

I've ordered a Crucial C300 hard drive to replace my ageing IDE drive as well, but since it uses SATA 3 and my radeon 5770 is currently on a PCI-E x16 2.0 lane, will both of them have to run at 8x? It can't be right, because SATA and PCI-E is different if I'm not mistaken?

Thanks in advance :)

Dark Mantis

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #1 on: July 04, 2010, 09:56:06 pm »
I have just checked the manual for that board and as far as I can see what you were told was wrong because the PCIe 16x bus is seperate to the PCIe bus that supports the SATA3 etc. So they do not share bandwidth.
Gigabyte X58A-UD7
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Dominators 1600 x6 12GB
6970 2GB
HX850
256GB SSD, Sam 1TB, WDB320GB
Blu-Ray
HAF 932

Gigabyte Z68X-UD5-B3
i7 3770K
Vengeance 1600 16GB
6950 2GB
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Justin

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #2 on: July 04, 2010, 10:00:04 pm »
Hmmm, maybe I'm not understanding this properly, but why does it still say something like that on the product page? So will I still get to use my radeon 5770 at full speed on the PCI-E x16 2.0 lane, whilst the SSD is also running at its fastest?

bottom note - http://www.gigabyte.com/products/product-page.aspx?pid=3439#sp

* When SATA3 / USB 3.0 (Marvell 9128 /NEC USB 3.0 Controllers) work at turbo mode, 1st PCIE x16 will work at x8 speed. " (My Crucial C300 has the marvel controller)

Dark Mantis

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #3 on: July 04, 2010, 10:13:33 pm »
Yes I see what you mean. I was basing my answer on the block diagram from the manual and on thta it shows the lanes as totally seperate. The PCIe graphics runs directly to the CPU and the Marvell controlled SATA3 lane runs to the P55 chipset. Therefore I can't see how one would interfere with the other. See here: http://download.gigabyte.eu/FileList/Manual/mb_manual_ga-p55a-ud3_v2.0_e.pdf
Maybe someone else will have a different viewpoint.
Gigabyte X58A-UD7
i7 920
Dominators 1600 x6 12GB
6970 2GB
HX850
256GB SSD, Sam 1TB, WDB320GB
Blu-Ray
HAF 932

Gigabyte Z68X-UD5-B3
i7 3770K
Vengeance 1600 16GB
6950 2GB
HCP1200W
Revo Drive x2, 1.5TB WDB RAID0
16x DLRW
StrikeX S7
Full water cooling
3 x 27" Iiy

Peteruk

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #4 on: July 05, 2010, 02:27:31 am »
The block diagram simply doesn’t show it but there is a BIOS option to force it to run off the P55 by disabling “Turbo SATA3 / USB3.0”. 

Dark Mantis

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #5 on: July 05, 2010, 06:28:50 am »
Ah, that explains it then. I did read the note at the bottom but it didn't seem to make sense. How did you find that out.
Gigabyte X58A-UD7
i7 920
Dominators 1600 x6 12GB
6970 2GB
HX850
256GB SSD, Sam 1TB, WDB320GB
Blu-Ray
HAF 932

Gigabyte Z68X-UD5-B3
i7 3770K
Vengeance 1600 16GB
6950 2GB
HCP1200W
Revo Drive x2, 1.5TB WDB RAID0
16x DLRW
StrikeX S7
Full water cooling
3 x 27" Iiy

Peteruk

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #6 on: July 05, 2010, 10:00:19 am »
Ah, that explains it then. I did read the note at the bottom but it didn't seem to make sense. How did you find that out.
Because theirs an option in the BIOS to make it make sense.

Justin

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #7 on: July 05, 2010, 10:01:59 pm »
Alright, I think I got it, so I will be able to use my GPU at a x16 2.0 lane, along with my SATA3 SSD at non-turbo mode? Is this correct?

Dark Mantis

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #8 on: July 05, 2010, 10:20:03 pm »
That's how I understand it from the description peteruk gave and obviously he checked!
Gigabyte X58A-UD7
i7 920
Dominators 1600 x6 12GB
6970 2GB
HX850
256GB SSD, Sam 1TB, WDB320GB
Blu-Ray
HAF 932

Gigabyte Z68X-UD5-B3
i7 3770K
Vengeance 1600 16GB
6950 2GB
HCP1200W
Revo Drive x2, 1.5TB WDB RAID0
16x DLRW
StrikeX S7
Full water cooling
3 x 27" Iiy

Justin

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #9 on: July 05, 2010, 10:33:26 pm »
What is "turbo" SATA3/USB3 anyway? If I disable it in the BIOS, what becomes of it? will it still run at the 6gb bandwidth?

Dark Mantis

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #10 on: July 05, 2010, 10:41:34 pm »
you will not be able to use the full SATA3 6Gb fully anyway even my SSD doesn't even get close to pushing it and theres next to no USB3 devices yet anyway.
Gigabyte X58A-UD7
i7 920
Dominators 1600 x6 12GB
6970 2GB
HX850
256GB SSD, Sam 1TB, WDB320GB
Blu-Ray
HAF 932

Gigabyte Z68X-UD5-B3
i7 3770K
Vengeance 1600 16GB
6950 2GB
HCP1200W
Revo Drive x2, 1.5TB WDB RAID0
16x DLRW
StrikeX S7
Full water cooling
3 x 27" Iiy

Justin

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #11 on: July 05, 2010, 10:53:31 pm »
right, thanks a lot for the clarification.

Peteruk

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #12 on: July 05, 2010, 11:57:02 pm »
Being that the PCI-e is 2.0 @8x speed would be the same as a PCI-e 1.1 slot @16x which when  gaming with a high end card like a HD 5870 does not decrease performance much if at all.

Even though you went for a Crucial C300 SSD which can break 3Gbps SATA speeds you should just use the Intel 3Gbps SATA ports.
« Last Edit: July 06, 2010, 12:11:15 am by Peteruk »

Dark Mantis

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #13 on: July 06, 2010, 08:51:22 am »
Being that the PCI-e is 2.0 @8x speed would be the same as a PCI-e 1.1 slot @16x which when  gaming with a high end card like a HD 5870 does not decrease performance much if at all.

Even though you went for a Crucial C300 SSD which can break 3Gbps SATA speeds you should just use the Intel 3Gbps SATA ports.
Good reply, although I would have to differ regarding the SSD speed. The theory is correct but in practice even the SATA3 spec'd SSDs like the Crucial never get up to the full throughput of 6Gbs.
Gigabyte X58A-UD7
i7 920
Dominators 1600 x6 12GB
6970 2GB
HX850
256GB SSD, Sam 1TB, WDB320GB
Blu-Ray
HAF 932

Gigabyte Z68X-UD5-B3
i7 3770K
Vengeance 1600 16GB
6950 2GB
HCP1200W
Revo Drive x2, 1.5TB WDB RAID0
16x DLRW
StrikeX S7
Full water cooling
3 x 27" Iiy

Peteruk

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Re: What is this "P55 Chipset PCI-E 2.0 16x limitation" ?
« Reply #14 on: July 06, 2010, 11:58:35 am »
Good reply, although I would have to differ regarding the SSD speed. The theory is correct but in practice even the SATA3 spec'd SSDs like the Crucial never get up to the full throughput of 6Gbs.
No not up to 6Gbs but passed 3Gbps.