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From: beckmann@s28.csrd.uiuc.edu (Carl J. Beckmann)
Newsgroups: comp.sys.mac.hardware
Subject: Re: How fast can the serial ports go?
Keywords: maximum throughput
Message-ID: <1991Feb7.185438.13253@csrd.uiuc.edu>
Date: 7 Feb 91 18:54:38 GMT
References: <1991Feb2.062244.3235@nntp-server.caltech.edu> <43760@ut-emx.uucp>
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>>Given that, how fast can you run the serial ports on the various
>>models of Mac?

>The Mac Plus specs give .92 megabits per second if clocked externally.

That sounds right.  The Z8530 manual says that a 4MHz clock can achieve
1 Mbit/s in one of the synchronous modes.  The master clock on the Mac's
SCC is not exactly 4 MHz, only 3.97 or something wierd like that (although
I don't know that this would decrease the rate of an externally clocked
synchronous transfer - ?).

The circuit diagram in Inside MacIntosh, Volume III shows some RC RF filtering
on the serial drivers and receivers, but the RC time constant is only on
the order of 20 nanoseconds or so, so probably doesn't slow things down any.