On Tue, Sep 04, 2007 at 12:41:00PM -0700, Paul Goyette wrote:
> 
> netbsd-GENERIC.MP, on the other hand, gets all the way through system 
> configuration, and just about when it is ready to start init, the system 
> just reboots.  Nothing displayed on the console, it just goes right to 
> power-on self-test.
> 

Try disabling acpi and see if it boots - I had a similar problem with
my Tyan S2895 motherboard.

> On the 3rd hand, a custom kernel built from sources updated as of today 
> at 1400 UTC gets to about the same point, but then drops into the kernel 
> debugger at Xlegacy_intr+0x?? (I forgot to write down the number).  The 
> (USB) keyboard is totally useless at that point.
> 

In the bios, try disabling or reserving irq 7.  On my motherboard this
seemed to be generating spurious interrupts continuously causing the
machine to keep entering the ISR recursively until the kernel ran out
of stack and rebooted.  The IRQ may be different for you - you should
get a clue from the panic as to which one it is.

-- 
Brett Lymn