[rescue] Survey: what do you want in _your_ SPARC?

[George Adkins]

> Yes, I'm learning that different is often the case, with this system.
> Frinstance the memory bank layout is unique, and I recall reading somewhere
> that SS5s don't require termination for internal drives but this Axil
> definitely does.  

Umm, the SS5  drives are SCA.  One normally cannot terminate SCA drives, the 
backplane provides termination.

You may be thinking of the SS2.  In an SS2, the motherboard provides 
termination, as the SCSI bus is actually in the traces on the board.  The 
ribbon cables are actually stubs (which is why they have to be very, very 
short.)  The external tail of the bus usually remains unterminated.  Because 
the signalling rate is slow (only 5 MB/sec), and it is very short (maybe 200 
mm), the bus can function adequately with only half-termination.  The 
confusion with these guys comes from the fact that if you put a single, 
terminated drive in them, (without any external devices attached) they will 
still work, because you now have a fully terminated bus (although it's 
concentrated all at one end.)  However, if you put a terminated drive in them 
and then terminate an external leg of the bus, you are now triple-terminated, 
and you can have problems maintaining the signal on the bus, leading to 
headaches. 

George