Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!sun!pitstop!sundc!seismo!uunet!mcvax!cernvax!davidj
From: davidj@cernvax.UUCP (davidj)
Newsgroups: comp.sys.transputer
Subject: Re: Inmos links, the C004 and everything.
Keywords: Transputer Links
Message-ID: <957@cernvax.UUCP>
Date: 13 Mar 89 07:38:23 GMT
References: <8903081315.AA10484@uk.ac.ox.prg>
Reply-To: davidj@cernvax.UUCP ()
Organization: CERN European Laboratory for Particle Physics, CH-1211 Geneva, Switzerland
Lines: 23

We are preparing a paper on Inmos Links which will be presented at the
'Computing in HEP' conference at Oxford in April.  However to summarise
quickly....

The T8 does not send an ack until 5-6 bit periods after receiving the
start bit. And does not send the following datya byte until 5-6 bit
periods after receiving an ack. Thus the cable connecting two t8's
has to be very short unless you want to drop the data rate. The 5-6
figure arises because of jitter on the signal and clock sync at each end
of the link. There are additinal factors due to cable delayt, buffer delay,
c004 delay and which direction the wind was blowing when you made the
measurements. We have derived a formula which accurately predicts the
transfer rate between: t8-t8, t8-t4, t4-t8 and t4-t4 - see the proceedingd
of the conference for more details....

The c004 slows down the data transmission as it resync'c the data before
forwarding it, the delay is approx 1.9 bit periods at 20 Mbps link speed


	Dave Jeffery

CERN
Geneva