7 Feb
2007
7 Feb
'07
6:41 p.m.
Chuck Guzis wrote:
On 7 Feb 2007 at 11:08, jim wrote:
any other observations on WW as far as clocking? I
know that
the more expensive stuff ran mini coax around the backplane
to get much better signals, but we just used regular old 32 or
whatever guage WW wires, sometimes 26 guage for high
current.
How about ECL? Moto used to advertise that the 10,000 series was
"wire-wrappable", but the WW samples I've seen have lots of twisted
pairs on them. Looks like a real pain to do.
Cheers,
Chuck
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The Cyber 170 series from CDC used twisted pair wire-wrap. I still have a
bunch of it. The wires were color coded for length. The early back planes
were hand wired using a machine like Al described. Later machines were more
automated and wired from a reel. Proper nightmare to troubleshoot. You had
to feel a wire through the mat since all wires were the same color.
The logic was standard MECL 10K. The normal and complement outputs made it
a natural to use as a differential transmitter. So some of the signals were
single-ended, twisted with a ground wire. The longer signals and I/O lines
used the twisted pair as a differential line - no ground wire. If I
remember correctly, the standard single ended wire was 100 ohm impedance
terminated to 220 ohm resistors to -2.2v or 550 ohm resistors to -5.5v. The
differential lines used two resistors at each end.
Real pain doesn't do justice to working with these back planes. The wires
were 30 gauge single strand and brittle. When removing one, you had to
carefully trim off the bare wire end before pulling the wire out of the mat.
If you didn't, the ends would break off and fall down the vertical back
plane until they disappeared. Then you got to spend an hour trying to find
them. We used to call them "tingles".
If you didn't get them all out and applied power, they became "twinkles" as
they shorted out and vaporized. Which did wonders for the logic and gave
you a couple more hours of overtime trying to get the machine going again.
Of course this always happened late on a Saturday night, especially if you
had a date or tickets.
Putting ECOs in became a total complete nightmare. We calculated the size
of work by number of wires to change. If you were good, you could do 8-10
wires an hour.
4 years of twisted pair wire wrap experience is probably the best
explanation I can give for volunteering to move off main frames and on to
disk drives.
Billy