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H67 / H61 PCIe lanes too few?

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May 10, 2011 6:40:07 PM

Hi there! :hello: 

Before I besiege you with my seemingly endless stream of n00bisms, I'd like to ask you how you all are doing, were doing, (for the especially clairvoyant, how you will have been doing) and apologize for having been rather lazy on the forums of late.

That having been said, the doubt tugs at the strings of my mind, and I place before you the question that biteth like a serpent, and stingeth like an adder.

OK, OK, maybe I exaggerate.
(Do with me bear, tis' too much of Shakespeare, I fear...) :pt1cable: 

Here's the deal:

I'm going to be building a machine based on the H61 chipset (budget constraints) for someone I know. They want Intel only, so no Llano, and definitely no Bulldozer... :pfff: 

AFAIK, the H61 chipset allows for a maximum of 6 PCIe lanes.

The problem is that I'd like to use one PCIe x1 slot for a USB 3.0 card, and leave another PCIe x1 slot for future expansion, like for a SATA 3 card. So if my understanding is correct, that's 2 of the 6 PCIe lanes already utilised, leaving 4 for the GPU. Now running any respectable GPU (say, a Radeon 6850) @ x4 seems almost sacrilegious to me. What is to be done?

Let us say I upgrade to the H67 chipset, and gain 2 PCIe lanes for a grand total of 8 PCIe lanes. SATA 3 + USB 3.0 are already on board so no add-on cards required for them, and the GPU is happily purring along @ x8.

Now, the fly in the ointment: if I understand this stuff correctly, the moment I insert a PCIe x1 card (for eSATA / Firewire / 802.11n capabilities), I am left with 7 PCIe lanes, and since PCIe devices use lanes in the powers of 2, the GPU begins to run @ x4 (as the closest power of 2 to the number 7 is 2^2 = 4), and not x8 as planned. Again, I find myself in a jam.

What to do?

Thanks for your time.

Have a great day! ;) 

More about : h67 h61 pcie lanes

a c 107 V Motherboard
May 10, 2011 11:40:40 PM

You're forgetting that the Sandy Bridge CPU has 16 PCIe lanes built in for graphics (either the integrated graphics or a discrete card). The lanes from the chipset are extra beyond that.
a c 97 V Motherboard
May 11, 2011 12:43:29 AM

Getting h67 with usb 3 and sata 3 would be cheaper than getting the add on cards; h67 is like $20 more over h61. Which shouldn't be a problem.
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May 11, 2011 1:54:31 PM

Leaps-from-Shadows said:
You're forgetting that the Sandy Bridge CPU has 16 PCIe lanes built in for graphics (either the integrated graphics or a discrete card). The lanes from the chipset are extra beyond that.


I don't think that's the case. Could you provide me a link to confirm what you said?
I think 16 PCIe lanes are the maximum supported by the LGA1155 CPU's.

How many of the available PCIe lanes can be utilised will then depend on the chipset.
The P67 chipset offers all 16 PCIe lanes for use. The H67, 8 lanes. And the H61, just 6.

Is that it or have I finally lost it? :??: 
May 11, 2011 1:58:40 PM

k1114 said:
Getting h67 with usb 3 and sata 3 would be cheaper than getting the add on cards; h67 is like $20 more over h61. Which shouldn't be a problem.


Yeah, I agree. Probably be going H67.

Thanks for the tip. :) 

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a c 107 V Motherboard
May 11, 2011 4:46:35 PM
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hmdhruvarora said:
I don't think that's the case. Could you provide me a link to confirm what you said?
I think 16 PCIe lanes are the maximum supported by the LGA1155 CPU's.

How many of the available PCIe lanes can be utilised will then depend on the chipset.
The P67 chipset offers all 16 PCIe lanes for use. The H67, 8 lanes. And the H61, just 6.

Tell me ... how could any graphics card have x16 PCIe connectivity if the chipset is the only source of PCIe and it only has six or eight PCIe lanes?

Every single consumer Sandy Bridge CPU has 16 PCIe lanes built in. The server (Xeon) chips have 20 PCIe lanes.
The lanes provided by the chipset are extra beyond that, used for USB3 ports, extra SATA3 ports, extra LAN ports, FireWire ports, Bluetooth, etc.



Upcoming Sandy Bridge "E" (SNB-E) processors will have 32 PCIe lanes built in, plus eight more from the X79 chipset.
a b V Motherboard
May 11, 2011 4:57:57 PM

There's probably only a couple h61 that could even support 3 pci cards because the gpu takes up two slots.

The one I have only has 1 pci-e and 0 pci.

If I could do it again, I would have gone H67, but for $59 I've had absolutely no problems with this board, and can't complain.
May 11, 2011 5:48:11 PM

Leaps-from-Shadows said:
Tell me ... how could any graphics card have x16 PCIe connectivity if the chipset is the only source of PCIe and it only has six or eight PCIe lanes?

Every single consumer Sandy Bridge CPU has 16 PCIe lanes built in. The server (Xeon) chips have 20 PCIe lanes.
The lanes provided by the chipset are extra beyond that, used for USB3 ports, extra SATA3 ports, extra LAN ports, FireWire ports, Bluetooth, etc.

http://images.anandtech.com/reviews/cpu/intel/sandybridge/review/chipsets.jpg

Upcoming Sandy Bridge "E" (SNB-E) processors will have 32 PCIe lanes built in, plus eight more from the X79 chipset.


:o 
Thanks for clearing that up. I did not know about that.
Ah well, my bad.

Just find it a little weird that the chipset can provide additional features that the CPU does not natively support.

Just so that I'm clear: the lanes that the chipset provides cannot be used for a GPU? Say, for instance, would it be possible to have a x16/x16 Crossfire / SLI on a P67 board?

And another question: how do I know which is which - which lanes are controlled directly by the CPU, and which are through the chipset?

Thanks for helping a n00b. :D 


a c 107 V Motherboard
May 12, 2011 1:20:11 AM

With the addition of the NF200 chip, some boards can do x16/x16 SLI and CF. The ASUS P8P67 WS Revolution is one such board.

The PCIe lanes in the CPU can only be used for graphics. Everything else goes through the chipset.

On a board with the NF200 chip, all of the CPU's lanes and some of the chipset's lanes (through the NF200) are used for graphics. The rest of the chipset's lanes are used for everything else. There is no performance penalty either way, so it doesn't really matter where the lanes originate.
May 12, 2011 4:31:04 PM

Best answer selected by hmdhruvarora.
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