Xref: utzoo comp.sys.atari.st:12013 rec.music.synth:4964
Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!wasatch!utah-gr!uplherc!sp7040!obie!wes
From: wes@obie.UUCP (Barnacle Wes)
Newsgroups: comp.sys.atari.st,rec.music.synth
Subject: Re: MIDI Networking
Summary: MIDI too slow for networking
Message-ID: <229@obie.UUCP>
Date: 19 Oct 88 06:42:56 GMT
References: <YXC6Ity00XoBI940VJ@andrew.cmu.edu> <3602@druhi.ATT.COM> <5080@saturn.ucsc.edu>
Organization: the Well of Souls
Lines: 35

In article <5080@saturn.ucsc.edu>, koreth@ssyx.ucsc.edu (Steven Grimm) writes:
> I had the opportunity to take a look at John DeMar's "ST-NET" in a very
> primitive form.  It was *SLOW*.  File service is slower than floppy access
> by a significant amount.  And that's with only two computers talking to
> each other; things will slow down even more when you add more computers
> to the net.  The problem isn't anything you can really solve in software;
> it's the 31Kbaud transmission rate of the MIDI port.

Consider this little GEM :-) gleaned from the Abacus "Atari ST Internals"
book:

Bits 0 and 1 of the Control Register on the MIDI 6850 chip control a
"divider" for the input clock, determining the baud rate.  The MIDI sets
these bits to 01, meaning divide the clock signal by 16.  The clock to
the 6850 is 500 Khz, which gives us the MIDI speed of 31250 bps.

If you reprogram these bits with 00, it tells the chip not to divide the
clock, giving you a clock of 500 Khz, which is adequate for a simple,
small network (like AppleTalk).

I have wanted to play with this for quite a while, but I have not been
able to find out what setting is used for the rest of the bits in the CR
on the 6850.  Can anyone tell me where the MIDI port is initialized by
the ROMs?  If you can give me an address, I can go disassemble the code
and find out what the CR is set to on initialization.  I'd like to see
of the rest of the circuits surrounding the 6850 can stand up to this
kind of speed.  It isn't all THAT high, but I'm not going to stick my
neck out until I've tried it personally.  This could make programs like
MIDI-NET much more usable if it works!

-- 
                     {hpda, uwmcsd1}!sp7040!obie!wes

         "How do you make the boat go when there's no wind?"
                                 -- Me --