Sun external SMD cables

Paul Koning paulkoning at
Fri Feb 14 16:00:21 CST 2020

> On Feb 14, 2020, at 4:54 PM, jim stephens via cctalk <cctalk at> 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.


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