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From: slsw2@cc.usu.edu
Newsgroups: comp.sys.dec.micro,comp.os.cpm
Subject: Re: cp/m 2.2 for rainbow
Message-ID: <1990Dec18.140017.45263@cc.usu.edu>
Date: 18 Dec 90 20:00:17 GMT
References: <1990Dec16.005742.25681@techbook.com>
Distribution: usa
Organization: Utah State University
Lines: 45

In article <1990Dec16.005742.25681@techbook.com>, fzsitvay@techbook.com (Frank Zsitvay) writes:
>    does anyone know if cp/m 2.2 (strickly z80, not cp/m 8/16) is available 
> for the rainbow??

I believe not. Read on.

>    if not, what differences are there between cp/m 2.2 and cp/m according to
> the rainbow??   how do i controll the i/o ports independent of cp/m on this
> machine??

The CP/M on the rainbow is CP/M-86 that knows how to run a Z80 job on the
Z80 side. Basically, if the file ends in .COM, it's run on the Z80. If it
ends in .CMD it's run on the 8086.

When things are running on the Z80, the BDOS and BIOS all execute on the 
8086; calls are made through a small shared RAM. This means that the Rainbow
has more TPA available for a Z80 program than any other CP/M machine.

On the down side, I never got the I/O byte to work correctly from Z80. 
Whenever I tried to talk to anything other than the screen with the I/O byte,
I would just get random garbage. This, combined with the extreme slowness
of the Rainbow's terminal emulation, convinced me to turn my Rainbow into
a DOS machine.

Most of the interesting I/O (hard disk, serial ports, etc.) are connected
to the 8086 and are therefore unavailable to the Z80 except by asking
permission of the 8086. The Z80 does, however, directly control the floppy
drives. Since so much of the machine is controlled by the 8086, I doubt
that there was ever a real CP/M 2.2 for it.

>    the msdos side of the machine doesn't exactly thrill me, but it would
> make a killer z80 cp/m machine.  (and if i can use the 8088 ram as a ram
> disk, it would be even better.)

You can use 8086 RAM as a RAM disk for both CP/M-86 and CP/M-80; I don't
remember how it's done, but you can install a program that creates a drive
M: of a specified size.
-- 
===============================================================================
Roger Ivie

35 S 300 W
Logan, Ut.  84321
(801) 752-8633
========================