Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!deimos.cis.ksu.edu!rutgers!cmcl2!ccnysci!alexis
From: alexis@ccnysci.UUCP (Alexis Rosen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: How fast can a MAC-SE drive a serial line?
Keywords: serial, fast
Message-ID: <1581@ccnysci.UUCP>
Date: 14 Apr 89 08:18:42 GMT
References: <13655@jumbo.dec.com> <28021@apple.Apple.COM> <1514@ccnysci.UUCP> <28564@apple.Apple.COM>
Reply-To: alexis@ccnysci.UUCP (Alexis Rosen)
Organization: City College of New York
Lines: 33

In article <28564@apple.Apple.COM> phil@Apple.COM (Phil Ronzone) writes:
>In article <1514@ccnysci.UUCP> alexis@ccnysci.UUCP (Alexis Rosen) writes:
>> [...] Both TOPS and Dayna would be surprised to hear that their
>>FlashTalk and DaynaTalk products, which run at 768 to 850 kbps, can't
>>ever go faster than 500 kbps.

Just to clarify things: The FlashTalk product definitely does 768Kbps.
(There are lots of nasty reasons you don't see 3x speedups on appletalk,
but the raw data goes out at that speed [except LAP packet enclosures]).

>The SCC has a clock MAXIMUM of 4 MHz (unless we have changed to a faster
>part lately). The SCC is clocked for baud rate generation at 3.673 MHz.
>AppleTalk, which uses SDLC phsyical transmission, runs as FM0 using the
>onboard PLL -- thus, at around 4MHZ, 230.4 KB is the fastest you can run
>the machine.
>
>In serial I/O, you need to sample at 16X the baud rate. The limiting
>factor is the divisor given to divide the clock rate and still sample at 16X.
>
>The SCC is a pretty interesting USUART, but for the current clock rates,
>SDLC in FM0 can't go faster than 230.4KB -- serial I think (can't remember)
>can be pushed to twice that.

Hm. Something I don't know about. What is "FM0" in this context?

Anyway (not that I mind the posting, but), what has this to do with the
original message? I guess we are just drawing a distinction between what
can be done with just a cable, and what you need a sync separator to do.


---
Alexis Rosen
alexis@ccnysci.{uucp,bitnet}