Runing out of PCIe Lanes?

Stereodude

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:erm: Is it possible to run out of PCIe lanes?

I installed a PCIe Intel Pro/1000 PT server card in my desktop and it doesn't appear in the device listing during boot sequence, nor in Windows. I tried it in two different PCIe x1 slots with the same results. It works in another system just fine, so I know the card isn't bad.

I'm running a Gigabyte P35-DS4. I have a nVidia 7900GS and a Dell Perc 5/i in my system. Presumably they are both running x8. When I pull the Dell Perc 5/i from the system the NiC shows in the device listing and in Windows. :scratch:
 

MaxBurn

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I think your video card is running X16 and can't shift those lanes down to something else because it is on another chip.

Supposedly there are 16 lanes total but some are in use that you can't change and the flexibility isn't there to shift things around like you want.

Similar experiences to yours:
http://www.tomshardware.com/forum/244273-30-ds3p-limited-express-lanes

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blakerwry

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I was under the impression that if there only X number of lanes then only that number of lanes could be implemented (physically via slots).

I thought this was the reason that many dual vid boards initially used two x8 slots.

It seems surprising that gigabyte would make a board that would turn off the x1 slots when the x4 slot was used (conclusion based on the comments from the tom's thread). Certainly this would have to be documented.

As a work around, you could try taping off some of the PCIe conductors to make an x4 or x16 card to make it work at a lower PCIe channel number (possibly freeing up channels for other slots). Exact conductor numbers can be found online (I think tom's did a test of x16 gfx cards at 1x, 2x, 4x, and 8x which illustrated this process).
 

MaxBurn

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I think I have the same problem on my G33 based board, but I like my built in Intel LAN. I only have a G260 and a PCIe X-Fi Titanium at the moment. I was toying with the idea of a PERC6/i and a couple X25M's when you all were discussing them a while back but I remembered this problem.
 

blakerwry

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page 10 of the manual (http://america.gigabyte.com.tw/FileList/Manual/motherboard_manual_ga-ep35-ds4_e.pdf) definitely states that the 3 PCIe x1 slots are shared with the second x16 slot (electrically an x4)

The diagram on page 8 seems to indicate that if the device installed in the second PCIe x16 slot is an x1 device then the 3 PCIe x1 slots should get their lanes.

The solution is to set your PERC to x1 (or possibly x2)... or get a different motherboard with more bandwidth.
 

MaxBurn

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Ah yes, note 2 is a killer:

(Note 2)When the second PCI Express x16 slot (PCIE_16_2) is in use, the three PCI Express x1 slots become unavailable.

I wouldn't think that taping would help, likely something in there decides if that port is in use and if so switches the lanes to that port, else the x1 lanes are enabled.
 

Stereodude

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The Perc is only doing RAID-1 with two drives.

I suppose I could put the drives on the Gigabyte / Jmicron SATA controller in RAID-1 (currently connected only to eSATA ports). That would leave me with only one free SATA port on the ICH9R that would be connected to an eSATA port.

ps: Who knew reading the manual would come in handy.
 

sechs

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For your convenience, they have attached PCI Express slots that you cannot use.

Kind of like the feng xue motherboard.
 

blakerwry

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I wouldn't think that taping would help, likely something in there decides if that port is in use and if so switches the lanes to that port, else the x1 lanes are enabled.


The diagram on page 8 shows that the second PCIe has a dedicated x1 lane and the other x3 lanes that go to that slot are switched with the 3 PCE x1 slots. If the manual is correct, then you can use four x1 devices (or one x4 device).

Other combinations may (wouldn't bet on it) be possible.
 
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