On 10/25/18 11:47 AM, Robert Nichols wrote: > On 10/25/2018 01:04 PM, Joe Zeff wrote: >> On 10/25/2018 11:47 AM, Rick Stevens wrote: >>> Or the jumper headers. Even the famous "0-ohm" resistors (a wire >>> with a fake resistor body with a single black band on it). Remember the >>> "/phantom" line (pin 67) to tri-state memory boards so the PROM would >>> present itself, overlying any RAM at that address? >> >> What? Not even a gold (I think it was.) band to show high precision? > > Ever try to make something that was "0 +/-5%"? How much is 5% of zero? > Even that 1/2" piece of copper wire would have _some_ resistance, > putting it out-of-spec. Which is why it didn't have tolerance or temperature bands. No tolerance band, +/- 20%. No temperature band, -10 to 100 degrees C. They were just created so automated insertion equipment could stuff jumpers into the boards. At Micropolis, we used them to do the drive select, although later we just stuffed in an 8-pin DIP header and had a DIP-packaged jumper pack with either pins 1-8 jumpered or 2-7 jumpered. The first, inserted properly, gave you drive select (DS) 0, plugged in backwards gave you DS3. The second, DS1 and DS2 respectively. IBM shipped all their drives jumpered for DS1 and did that funky, weird twist in the ribbon cable to give you DS0 (flipped the DS0 and DS1 signals). Pretty stupid, if you ask me. ---------------------------------------------------------------------- - Rick Stevens, Systems Engineer, AllDigital ricks@xxxxxxxxxxxxxx - - AIM/Skype: therps2 ICQ: 226437340 Yahoo: origrps2 - - - - "Celibacy is not hereditary." - - -- Guy Goden - ---------------------------------------------------------------------- _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx
