14 Dec
1999
14 Dec
'99
4:25 p.m.
At 03:24 PM 12/14/99 -0500, CLASSICCMP (Tim Shoppa) wrote:
Oh well.
Does anyone
know if the CONFIGURE command in the VAX prom suggests slot
ordering in its output?
No, it doesn't. The order of CSR's doesn't have any bearing with what
cards go where in the backplane. The order of cards in the backplane will depend on
interrupt and DMA
priority. Generally, peripherals that *will* lose data if they can't get
serviced in time get put closest to the CPU. Examples here are serial
lines, etc. Next come peripherals that will have to do a retry if they
don't get serviced in time, but they will be able to do a retry. Tape
drives, for example, might come here. Finally come devices where there's
no real penalty for a retry, and maybe the peripheral doesn't care at all
if the CPU takes its own sweet time in dealing with it. Something like
a real-time clock would come in this category.
Sigh, I read Alan's paper and it explained why things are the way they are
but it didn't help me figure out what the ordering should be since I don't
have enough technical specs on some of the cards to know what their
"latency tolerance" is.
FWIW, the DZV11 was apparently already set up to be the "first" one (I
stuck it in and did a show QBUS and there it was). That saved me from
having to figure out the switch settings. And so far it seems to not be
interfering with the operation of the system.
--Chuck