21 Jan
2007
21 Jan
'07
8:09 p.m.
Two thoughts... SCSI IDs are send by a 1-of-N code on
the data lines,
so
the fact that devices show up at the correct IDs means that the host
can
assert data lines.
That's similar to what I was thinking
But 191 is 10111111 (hex BF) IIRC. Now that seems to be a significant
bit
pattern, particularly as bit 6 is the '0' -- your host adapater
wouldn't
happen to be device 6 on the SCIS bus, would it? (it's a common address
for the host adapter). Do you have any idea what the 'Type' should be?
SGIs all have the SCSI host adaptor at SCSI ID 0. Generally, the PROM
matches known types to user-identifiable strings (e.g. SCSI Disk:
dksc(0,1); SCSI Tape: dksc(0,4))
I know that CD-ROM devices were not included in the PROM, and they
appear as
"Unknown SCSI type 5 / removable: SCSI (0,6)" [or whatever the address
is], which correlates to the decimal conversion of the "Perepheral
Device Type" field returned in byte 0 by the inquiry command
(CD-ROM=0x5).
I'm not sure where 0xBF is coming from- that doesn't look like a valid
type. So there must either be a spurious signal (or excessive skew) or
a bad host controller. It sounds like the 0xBF is being reported for
all types, including a tape drive (should be 0x1), ZIP, and something
else that I can't find in an email right now, but I think it was a MO.
bear made a suggestion that it might be a problem with the termpwr.
Hmm- he says he's already desoldered the 33C93A and put in a socket, so
I might just go ahead and scavenge another 33C93A from a board in the
garage and send it to him (the PI owner, not bear).