14 Feb
2020
14 Feb
'20
2 p.m.
On Feb 14, 2020, at 4:54 PM, jim stephens via cctalk
<cctalk at classiccmp.org> wrote:
...
The SCSI spec and cabling have a specific way that the conductors have to be rolled to
make a round cable. Each cable type has a recommended way that signal and grounds should
be paired and in what proximity in the cable.
For SMD I never saw a formal spec with as much detail as the SCSI spec, and I don't
know if they standardized the cabling. Mainly to speculate about whether you can use a
generic 25-25 or 37-37 straight thru.
I suspect the 25-25 would be sensitive to the type of conductor pairing and fabrication
would work.
That reminds me of a situation I ran into about 20 years ago, working for a small router
company. They had a long spool of Ethernet cable to verify correct operation with max
length cables. But things were not working right. At some point I inspected the
connectors and noticed the pairs were connected to pins 1-2, 3-4, 5-6, 7-8. So two of the
Ethernet pairs were split, since the correct pairing is 1-2, 3-6, 4-5, 7-8. I cut off the
connectors and described the correct way; once new connectors were put on correctly the
tests passed.
paul