[CentOS] Tyan S2891 and CentOS -- 6, 8, 10+ PCI busses in today's new systems

Thu Dec 1 22:10:31 UTC 2005
Bryan J. Smith <thebs413 at earthlink.net>

rik at harddata.com wrote:
> Thanks for the hints on using pci=.  I got it to work.
> I couldn't find where pci=bios was documented but that
> option didn't work.

Boot Prompt HOWTO, Section 4:  
  http://www.tldp.org/HOWTO/BootPrompt-HOWTO-4.html  

> I read in the kernel docs in regards to booting and tried
> pci=conf1 and this worked.

>From the HOWTO ...

  4.2 The `pci=bios' and `pci=nobios' Arguments
  These are used to set/clear the flag indicating that
  the PCI probing is to take place via the PCI BIOS.
  The default is to use the BIOS.
  4.3 The `pci=conf1' and `pci=conf2' Arguments
  If PCI direct mode is enabled, the use of these enables
  either configuration Type 1 or Type 2. These implicitly
  clear the PCI BIOS probe flag (i.e. `pci=nobios') too. 

So you actually want to use "pci=nobios" (my bad).

I think I remember talking about this in the previous S2895
thread, how the default changed from 2.4 to 2.6.  In any
case, I'm going to do more complete research before putting
it in the ELManager's FAQ.

As I've told others, I don't always have the correct, exact
answer, but I like to think I get people on the right track.

> The machine is up and running and doing well under testing.

> I don't know what conf1 means but I be darned if it doesn't
> work :)

It was the BIOS preventing Linux from enumerating the PCI
busses and devices correctly.  So by passing "pci=conf1", you
effectively sent "pci=nobios" and blocked it.  It was the
exact opposite of what I was thinking.

Although it might be because 2.4 (CentOS 3) and 2.6 (CentOS
4) differ on defaults -- IIRC.



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