Any Z97 motherboards with 2x PCI x8 and 1x PCI x4 running at the same time

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davidst99

Senior member
Apr 20, 2007
217
0
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Hi,

Are there any new Z97 motherboards that can run 2x PCI at x8 and 1 PCI at x4? All the motherboards I found that if you want to run run a 3rd PCI at x4 it will take one of the other PCI slots and run it at x4 too instead of x8. Thanks.

David
 
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A I

A I

Senior member
May 20, 2004
491
2
81
Isn't it a limitation of the chipset to be 1x16, 2x8, or 1x8 + 2x4?
 
A I

A I

Senior member
May 20, 2004
491
2
81
You might want to check out the Asus Z97-WS or if there's another board that uses a PLX switch.
 
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davidst99

Senior member
Apr 20, 2007
217
0
71
Thanks for the info and links. I found a few Asus Z97 motherboards that can do 8/8/4. I would like to add a storage device to the third pcie slot but it would make my motherboard run at 8/4/4 mode and I would lose a lot of performance with my GTX670 SLI configuration. I should of been more clear in my question. I asked about the performance hit in the Video Cards and Graphics sub forum. Thanks again.

David
 
B

BD2003

Lifer
Oct 9, 1999
16,815
1
81
The gigabyte gaming 3 and gaming 5 do. Since they're not packed with a billion SATA and USB ports, there's lots of PCIE lanes left.

PCIE1 runs at 16x if there's nothing in PCIE2. Both run at 8x if there's two cards.

But with PCIE 3, its a choice between using it as x4, or using the 4 1x slots. I've got no need for the x1 slots, so I'm fine with that tradeoff.

It's a great configuration - you can run a physx card or a full speed nvme SSD in the x4 slot without affecting the bandwidth of the other two slots.

And they're inexpensive boards too, like $150ish. As far as I can tell, the only thing the 5 offers over the 3 is higher quality caps and gold plating on the audio jacks.


I don't have the board, just going by the spec sheets:

1 x PCI Express x16 slot, running at x16 (PCIEX16)
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.

1 x PCI Express x16 slot, running at x8 (PCIEX8)
* The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode. (The PCIEX16 and PCIEX8 slots conform to PCI Express 3.0 standard.)

1 x PCI Express x16 slot, running at x4 (PCIEX4)
* The PCIEX4 slot shares bandwidth with all PCI Express x1 slots. All PCI Express x1 slots will become unavailable when a PCIe x4 expansion card is installed.
* When installing a x8 or above card in the PCIEX4 slot, make sure to set PCIE Slot Configuration (PCH) in BIOS Setup to x4. (Refer to Chapter 2, "BIOS Setup," "Peripherals," for more information.)

3 x PCI Express x1 slots
(The PCIEX4 and PCI Express x1 slots conform to PCI Express 2.0 standard.)

1 x PCI slot
 
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evilr00t

Member
Nov 5, 2013
29
8
81
Here's some interesting info for the Haswell consumer/desktop platform:

The CPU itself only has 16 lanes of PCIe gen3. This can be bifurcated into:
x16
x8+x8
x8+x4+x4

The PCH has 8 lanes of PCIe gen2. This is linked to the CPU via DMI (~x4 Gen2 speed). These are divided into two "bifurcation sets":
x4
x2+x2
x2+x1+x1
x1+x1+x1+x1
Most manufacturers use four lanes (in x1x1x1x1) for onboard components, and leave a set of 4 lanes to be used in a higher bandwidth slot.

Is it possible to run two x8 and one x4? yes, if you use x8x8 on cpu and x4 on the PCH.

Now the interesting thing is that Ivy Bridge-DT supported 20 lanes of PCIe on the Xeon SKUs, but no one implemented them. Haswell-DT Xeon SKUs now only support 16 lanes... scumbag Intel.

Incidentally, putting a NVMe drive on the x4 PCH port is a bottleneck when they can do 2.8GB/sec (P3700 series).
 
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