If I recall correctly, the two processors need to be identical in order
to run.  I think the Z50 and the Z55 have different clock rates, but
I'm not sure.  Cache, etc., may also have something to do with it.

Bottom line:  If they're not identical, they probably won't work.

Hubert Feyrer sez:
/*
 * 
 * Hi,
 * 
 * I got my second CPU for my SS10 today, and have trouble getting it to run.
 * When I boot my machine with the old CPU (only), the banner says 1x390Z55
 * detected. With (only) the new one, it says 1x390Z50. With both, it does
 * 
 *  - not do anything at all, if the new one is the upper of the two boards,
 *    and the old one is below
 *  - boot only with the Z50 if the new one is the lower of the two boards,
 *    and the new one is over it. Solaris 7's mpstat gave me only 1 CPU. 
 * 
 * Here's what I can tell from the CPU boards:
 * the "old" one (seems to be a '41 modell):
 * 	This has two big ICs mounted, one black labelled Super SPARC
 * 	Cache Controller TMS390, and one gold labelled Super SPARC
 * 	Microprocessor TMS390. Plus 4 small ICs with "CXK77910J-20
 * 	249B54E^W" on them.

That would be your processor cache.  The '41s had something like a 1MB
total CPU cache (or was it 1MB for each instructions and data?).

 * the "new" one (might be a '40 model?):
 * 	This has onely one big black IC, labelled SuperSPARC
 * 	Microprocessor TMS390, plus some capacitors. Two tiny ICs(?)
 * 	labelled PE-53189 CHINA 9307-S.

That might be a '30; I don't recall that they made a plain '40 (at least
not initially).  They made models 30, 41, 52 and 54, each just enough
different so that you HAD to pay the higher premiums for the higher
revs.

 * 
 * Do I have to set any jumpers, or set something at the monitor prompt? 
 * Any help appreciated! :>

If you find out, let us know -- certainly that information might come in
handy if, for some silly reason, I end up in a similar situation with
respect to hardware.

 */





				--*greywolf;
--
BSD -> Solaris:		It could be worse.
UNIX -> NT:		It's worse.