[SunRescue] Ross SM100 CPU Module Question

[James Lockwood]

On Thu, 3 Jun 1999, joshua grubman wrote:

> james -
> 
> do you have the specs required to do this?

Yes.  There are four things to worry about when doing this:

VME data bus contention
VME control line contention (such as VME.RST.IN)
P2 bus contention
Power and cooling

The "easy" way to do it is the following: put each board on a seperate P2
segment, disable internal VME arbitration (J1701-1705), disable all VME
interrupts (J1801), disable system reset propagation (J1706), disable VME
slot-1 mastering (J1803) and pull the BG and IACK jumpers on a slot in
between each board for good measure. 

You can work around VME contention more easily than P2 contention,
technically you should not even need to pull BG/IACK on an intermediate
slot.  I _think_ that there is an easy way to disable the P2 bus on a 600,
but I'd have to dig through my schematics to find out.  This would let you
cram 8 boards in a chassis (16 slot) instead of 4 (the max number of
seperate P2 busses).  I always wondered why Sun decided to go with Sparc
10's for the SparcCluster 1 instead of a mess of 4/600 boards.

If you are up to cutting traces you must be careful, some of the lines
don't like to float.  Read the VME specs for details.  Note that if you
want to have any other cards in the system besides CPU cards (and
memory-only P2 cards) then things get complicated fast.  It's doable but
not easy.

-James