On Mon, 4 Apr 2005 21:35:55 -0400
Michael <macallan18@earthlink.net> wrote:

> 
> What kind of card is it ( besides sitting in the L2 slot ) - does it
> need any additional software to be recognized by MacOS? If so - does
> it leave anything funny in OF's nvramrc or something like that? If
> you're lucky this thing can be enabled with some OF voodoo ( Tim?
> You're the OF guru. )

Dan LaBell clearly knows more than I do about OF and Forth. I do know
that OF does expect to be on one CPU only, so I don't think it's set up
to switch CPUs. I have a 7200 that used to have a Sonnet G3 upgrade card
(which was horribly unreliable) and as far as I could tell, the switch
to the PCI card-based CPU only occured after the extension was loaded
by MacOS. If I had to guess, there has to be some write to a PCI
register that then turns the CPU on, and from there some renegotiation
of PCI bus mastering occurs or something that allows the second CPU to
become the primary one. The new CPU gets the same register contents as
the old one and resumes execution of the OS. Sort of a fork of the OS,
with the parent then turning off external interrupts on the old CPU.

tim