Re(2): Re(2): Re(2): [SunRescue] 4/6xx capabilities?

[Tim Hauber]

rescue at sunhelp.org,Internet writes:
>  Well, yes and no. In the P2 connector, the b row is VME signals, and the
>a and c rows are "user defined". Sun busses them between slots in ways
>that
>depend on the backplane. In everything six slots and wider, it is broken
>up
>into two or more segments. In the segment which contains the CPU, those
>pins are used for the memory bus. There is usually a second multi-slot
>segment which is used for other groups of board which need a private way
>to
>communicate (e.g. framebuffer/GP/GB combinations). In the 12-plus-slot
>backplanes, there are usually some slots in the middle where those pins
>are
>not connected to anything. In the case of slot 7 on x60 and x80
>backplanes,
>they're used as the SCSI passthrough, but if you have no SCSI devices
>hooked up, it's as "normal" as any of the other slots where rows a and c
>of
>P2 are not connected to anything.
>
>   --James B.

Well that helps, somehow I had in my head that b was user defined stuff,
which was why Sun used them for SCSI.  I hadn't understood that slot 7 has
no P2 connector from a VME standpoint.