🚀 go-pugleaf

chifang@sybil.cs.Buffalo.EDU (chi fang) writes:
: 
:          We have been adding external SCSI-2 FAST (10 MBytes/sec)
:          disks to our new SPARCstation 10. We can achieve reliable
:          operation
:          of one external SCSI-2 fast disk, but when we operate
:          more than one device externally we see data errors
:          and can't operate the disks in the SCSI Fast (10 Mbytes
:          /sec) mode.
: 
:          We have checked the usual cables, terminators, etc. and
:          we believe we are following all the rules.
: 
:          Any comments appreciated.   Anybody else having similar
:          problems?????

Chi,

	It seems that folks are finding out, after the fact, that FAST-SCSI-2
device buses will work at 10MB/sec speed but there are problems with running
them Single-ended as opposed to differential. We have found that FAST-SCSI-2
single ended interfaces (like the one on Sparc 10) will run properly at a
maximum bus length of about 1 meter or 2 to 2.5 feet. After that, even with
proper cables and terminators the BUS will experience errors and kick down
to one of the slower speeds like 7.0 MB/sec.

	Most companies that have properly researched and tested FAST-SCSI-2
have released the bus option only in a differential format (HP being an 
excellent example). In differential mode the logic voltages are increased
making greater data integrity across long distances (60 to 80 feet).
Performance Technologies sells Fast-SCSI-2 boards for SparcStations including
the 10 that go on the SBUS. They have both single-ended and differential.
They have strongly suggested going differential wherever possible. I would
suggest either purchasing the PT SBS430-D differential Fast-SCSI-2 board for
your SS10, or removing some devices and limiting your bus to one external
device with a cable length under 2 feet.

	If you cannot easily find a Performance Technologies board let me know
we can provide you with one. Performance Technoligies is on the net and if
they dont respond here they are usually in comp.sys.sun.hardware

Performance Technologies is pt.com

-Best Regards,

Jeff Johnson
Director of Engineering
Technikgruppenfuhrer <-(Deutsch)
Western Scientific
jeff@wsm.com