keeney@vixvax.mgi.com (Richard Keeney) (12/07/90)
I am looking for information on what is the difference between the standard gray colored SCSI terminator plug and the black SCSI terminator plug that Apple uses on the Macintosh IIFX. So far, the best information I have is a guess that it has something to do with how the terminators are powered (i.e. no diode or something like that). Exact technical details or a source of exact technical details would be appreciated. -- Richard A. Keeney Internet: keeney@mgi.com Management Graphics, Inc. Phone: +1-612-854-1220 1401 East 79th Street, #6 Fax: +1-612-854-6913 Bloomington, MN, 55425 U.S.A.
urlichs@smurf.sub.org (Matthias Urlichs) (12/10/90)
In comp.periphs.scsi, article <1990Dec6.153735.521@vixvax.mgi.com>,
keeney@vixvax.mgi.com (Richard Keeney) writes:
< I am looking for information on what is the difference between the
< standard gray colored SCSI terminator plug and the black SCSI terminator
< plug that Apple uses on the Macintosh IIFX. So far, the best information
< I have is a guess that it has something to do with how the terminators are
< powered (i.e. no diode or something like that). Exact technical details
< or a source of exact technical details would be appreciated.
<
The black terminators introduce some condensators to buffer the resistors'
power supply, which could be travelling from the Mac all the way through your
SCSI cable if no other device provides terminator power.
If the condensators aren't present, simultaneous changes on many lines
(data!) can cause glitches on other lines (notably REQ, which signal that the
data are ready). At that point, however, they usually aren't --> big problem.
--
Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de /(o\
Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(0700-2330) \o)/steveh@tasman.cc.utas.edu.au (Steven Howell) (12/18/90)
A black terminator is for high speed and contains a lower resistance termination block to prevent reflections being reflected back down the line. The standard terminators are a higher resistance, 220ohmsH and 330ohmsL. To date I have found 3 diffrent valu's for the black, being 100ohmsL,120ohmsL 180ohmsL and 120ohmsH,160ohmsH,200ohmsH respectivly.