12 Dec
1999
12 Dec
'99
11:08 a.m.
At 07:41 PM 12/12/99 +0000, Eric Smith wrote:
Chuck McManis <cmcmanis(a)mcmanis.com> wrote:
Well, I "liberated" a couple of 2+ GB drives (Seagates) from a Sun 490 disk
tray that suggest they are differential SCSI. I could live with 4GB :-).
Its intereface termination resistors are plug in sips. I wonder if they
used the trick where you replace the four rows of sips with a single DIP
terminator to switch it to an SE bus. TransTech still has a web site but so
far no word from their Support email.
Another interesting bit is that it is a QDT so presumably it is disk and
tape, but I don't think I've ever seen a differential tape drive. Perhaps
they assume the tape drive has the converter on it.
2) It has an NCR53C90 SCSI interface, and 18
nat'l semi 75176BN chips
wired up to the 50 pin connector. (I'm hoping these are differential
drivers for FAST SCSI II drives)
There's good news and bad news. The good news is that yes, those definitely
are differential transceivers.
The bad news is that FAST SCSI 2 is *NOT* differential. It's single
ended. 99.9% of the drives you're likely to encounter are single-ended.
Differential and single-ended will not mix [1]. It sounds like this controller will ONLY work with
differential drives,
unless they provided some sort of jumper arrangement to bypass the
differential transceivers.
To be determined.
There exist single-ended to differential converters,
but they're very
expensive.
Actually I recall that Disk Drive Depot sells them fairly cheaply. (less
than $20 as I recall)
--Chuck