BIOS detection of PCIe Bridge

taby2b · 04-07-2011, 04:19 PM

I spent all day yesterday trying to figure out why the PCIe expansion (bridge) card I bought was not being detected by my BIOS (and ultimately my RHEL5.4 OS). It was not until I actually plugged something into the expansion card that the bridge itself and the expanded PCIe component were detected.

I have tested and re-tested this issue.

My question is this: Why must I have a PCIe component connected to the bridge for the BIOS (and OS) to detect the bridge itself (and the connected PCI component) ?

Thanks.

stress_junkie · 04-08-2011, 08:53 AM

What method are you using to determine that the card is or is not detected by the BIOS? I would use the dmidecode utility while running Linux.

taby2b · 04-08-2011, 11:16 AM

Quote:

Originally Posted by stress_junkie

What method are you using to determine that the card is or is not detected by the BIOS? I would use the dmidecode utility while running Linux.

The BIOS has the ability to display the IRQ number assigned to detected components. When the PCIe interface card is connected to a PCIe component the BIOS shows me the IRQ number assigned to both the PCIe card and component. Conversely, when disconnected neither card nor component even show up in this display. The lack of IRQ assignment leads me to believe that the BIOS does not detect the PCIe interface card.

Latios · 04-08-2011, 11:36 AM

IDK maybe some excessive "smartness" to turn off the bus if no cards are present ?

I would not think so cause a lot of stuff built into the mainboard (ethernet / sound / maybe something else) are PCI or PCIE too