Hello Paul,

  PTS> ok so if it's a more modern standard it won't work yeah?

I think it's a coin toss basically.  I've heard it said that Ultra160
drives are supposed to be able to fall back to single-ended signalling
but I don't know how safe it is to assume that they can also work on a
narrow (8-bit) bus.  I'm interested in finding out though, not least
because the drive in my own SPARCstation 5 is old, small and screechy.

  PTS> yeah the SCA plug has nothing on it.

But it's still connected to the bus? I think I read somewhere that SCA
drives ordinarily let the backplane control ID numbers and that the
drives are unterminated, depending on the backplane to terminate the
SCSI bus.  If this is true, then even if there's no drive plugged into
an SCA backplane, it's not safe to assume that there's no termination
there.

If I get time when I get home tomorrow morning, I'll tear apart my
SPARCstation5 in an attempt to determine how the SCSI bus is routed.
One end is bound to be the external SCSI port on the back, perhaps via
some sort of automatic termination? The bus presumably goes from there
to the SPARCstation's host adaptor chip and then to a header where it
jumps off as a ribbon cable.  My guess would be that the ribbon cable
goes to the CD-ROM drive and then to the SCA backplane where it's
terminated at the physical end.  It could be the other way around
though.  Hopefully the CD-ROM isn't on a spur.

- Andy.