Tom's Hardware > Forum > Motherboards & Memory > Chipsets & Bios > Intel Chipset Limitation: No Video During Post w/ PCIe x16 slot use?

Intel Chipset Limitation: No Video During Post w/ PCIe x16 slot use?

Forum Motherboards & Memory : Chipsets & Bios - Intel Chipset Limitation: No Video During Post w/ PCIe x16 slot use?

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gerhardb   11-11-2009 at 11:59:08 PM

Ok,

So I've been dealing with Asus and a problem: (This is no longer an Asus thread...)

Basically, I've got an Intel based motherboard (G41 Northbridge / ICH7R Southbridge), and the IGM integrated Intel Graphics.

This board has HDMI / DVI / VGA.

The issue is that if I put ANY PCIe card in the x16 PCIe slot, NO DIGITAL VIDEO WILL DISPLAY DURING POST.

(In otherwords, the HDMI and/or DVI ports do not work. In fact, they don't work at all unless you boot to a GUI based OS with the Intel video drivers installed.)

Asus is telling the this is a FLAW in the Intel chipsets, period... and that NO Intel motherboard will display digital video during POST WHEN A PCIe CARD IS INSTALLED IN THE x16 PCIe slot.

In my case, I'm using the Intel based board (a P5QPL-VM EPU) as a home Linux appliance, and needed to multihome the box. So I installed an Intel PCIe NIC in the PCIe x16 slot... (it's a x4 card...)

Had anyone else heard about this [according to Asus] universal failure of all Intel chipsets to support Digital (not VGA) video during POST when using the x16 PCIe card slot with anything by a video card??

Frankly, it seems unbelievable...

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roonj   11-16-2009 at 03:40:44 AM

If I understood you, they say the onboard DVI port is driven by the IGP.
Therefore when you install a discrete video card (which normally disables IGP chips)or other PCI-e card in that slot the DVI which only runs from the IGP doesn't work.
Sorry sounds right or I may have misunderstood.

Reply to roonj
gerhardb   11-16-2009 at 04:46:45 AM

ahhhh, but the issue here is that you STILL get VGA (analog video) when using the x16 card.

...and of course, the specification for x16 PCIe card slots does include being about to use other cards.

In the borard, you can not use DVI or HDMI, only VGA during POST.

Reply to gerhardb
tcsenter   11-16-2009 at 12:21:39 PM

gerhardb wrote :

(In otherwords, the HDMI and/or DVI ports do not work. In fact, they don't work at all unless you boot to a GUI based OS with the Intel video drivers installed.)

Asus is telling the this is a FLAW in the Intel chipsets, period... and that NO Intel motherboard will display digital video during POST WHEN A PCIe CARD IS INSTALLED IN THE x16 PCIe slot.


That is correct, its an Intel chipset limitation. The G41/43 chipsets are an improvement here, as the previous IGP chipsets such as G33/G31 completely disabled digital output from the IGP when inserting any card wider than PCI-E x1 into the native PEG x16 slot. At least with the G41/43, you get digital output working via the Intel driver.

Reply to tcsenter
gerhardb   11-19-2009 at 07:33:09 PM

Ok.... that's pathetic...

Man...

Of course, I'm more annoyed that Asus does not put a disclaimer on the box indicating that you will not be able to use the PCIe x16 slot for anything if you want digital video.

This does explain why you don't see many boards with anything other than a VGA connector.

GB

Reply to gerhardb
tcsenter   11-19-2009 at 11:51:04 PM

The reason is because Intel designed its IGP to support those ADD2 SDVO add-in cards for additional display functionality. The IGP digital output actually gets rerouted to the ADD2 card via some built-in switch in order to provide the display output. So the IGP display controller is literally wired (multiplexed) into the native PCI Express 16 interface located in the Northbridge.

A few boards get around this by not using the native PEG interface in the Northbridge to provide the PCI Express x16 slot. They reroute x4 lanes from the ICH Southbridge in order to provide the PCI Express x16 slot (but this limits all cards installed there to x4 operation). Gigabyte has at least one board that does this.

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