> hmm... I don't know about the firmware version. Though '2.1' rings a bell
> but I could be way out to lunch.
> 
> but MBUS speed is interesting. I'll check that too.


Well, at least in the SS10 and SS20, the boot PROM sets the MBus speed
for you.  Interestingly, the 150 HyperSparc has MBus set to 40MHz, while
a 125 MHz module gets an MBus speed of 50 MHz.  (That's in the SS20;
SS10 is hardware limited to 40MHz max MBus speed.)  

I guess the 150 MHz clock was pushing things enough already for the
time; they didn't want to additionally stress the system with a 50MHz
bus clock.

Regarding boot PROMs: the 150 MHz module requires OBP 2.25, while the
125 module only needs 2.22.  Don't know about the 100 MHz modules, and I
certainly don't know anything about 4/690-specific issues.

Adrian Cockroft's book has some things to say on this; you might look it
up.

-David.