Date   : Thu, 23 Aug 1990 20:02:06 GMT
From   : swrinde!cs.utexas.edu!hellgate.utah.edu!cc.utah.edu!cc.usu.edu!slsw2@ucsd.edu (Roger Ivie)
Subject: Z80 multitask

In article <3696@ruuinf.cs.ruu.nl>, clldomps@praxis.cs.ruu.nl (Louis van
Dompselaar) writes:

> Is there anyone who has had some experience in using multitasking
> on a Z80 system? Please let me know what is, and what is not, possible...

I've done two multi-tasking things on a Z80. The first is that I experimented
with MP/M on an Apple Softcard; I wrote a simple MP/M BIOS that simply called
the CP/M BIOS. I had two jobs going: one just barely large enough to load
Microsoft BASIC and the other just barely large enough to run PIP when 
BASIC was loaded in the other. It was lots of fun.

You might still be able to get MP/M. I bought a brand new copy about a year
ago, but still have yet to do anything with it. I intend to eventually get
it running on my NorthStar; I seem to keep collecting bankswitched memory
cards for the thing.

The other thing I've done with multitasking was for an embedded system. The
company I work for makes an IEEE-488 interface to the VAXBI whereon the
IEEE-488 is entirely managed by a Z80 (i.e.: the VAX politely requests that
the Z80 do the work for it. Not fast, but it did make the BI interface
very simple. Oh yeah; the Z80 knows how to translate VAX virtual addresses;
that was fun). The whole thing is written in assembler and uses a decendant
of an 8080 multi-tasking kernel originally published in BYTE back when BYTE
published that sort of thing.
-- 
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Roger Ivie

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Logan, Ut.  84321
(801) 752-8633
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