AMD64 Stable fails to boot on Dell PowerEdge 1950

[Travis Pugh]

Hi folks.  I have read of some issues with the Dell PE1950/2950s in the 
archive, but nothing like this.  I have a Dell PowerEdge 1950 with 2 
dual-core Xeon 5050 processors, with SATA drives attached to the Dell 
SAS5/i controller.

I'm trying to load 6.1-STABLE-200609 AMD64 on the machine.  It loaded 
fine on a 2950 with the PERC5/i, but it won't load on this host without 
disabling ACPI.

Booting with ACPI enabled and verbose logging, the kernel gets through:

lo0: bpf attached
rr232x: no controller detected

and then hangs.  The keyboard (USB) becomes unresponsive, and a hard 
power cycle is necessary.

Booting with ACPI disabled, it recognizes da0 after the bpf message, and 
moves on to install.  The issue here is that it does not recognize any 
of the additional processors or cores with ACPI disabled, turning a 
4-way machine into a single processor device.  It appears that with ACPI 
enabled, the kernel isn't initializing or recognizing the SAS disks.

I tried HEAD, and it displays the same behavior.

Is there something I'm missing with regards to ACPI on the AMD64 
platform?  I've read here that i386 boots fine on the same hardware.

Thanks.

-travis