Date   : Mon, 06 Feb 1989 22:11:50 GMT
From   : cadnetix.COM!cadnetix!rusty@uunet.uu.net (Rusty)
Subject: Z80 Co-processors

In article <8902021749.AA09055@freedom.llnl.gov> rzh@FREEDOM.LLNL.GOV (Roger
H. Hanscom (415) 423-0441) writes:
>
>Does anybody out there have any experience with Z-80
>co-processors of the type that plug into the PC buss??
...
>I got a catalog in the mail last night from Central
>Computer Products.  The co-processor that they carry
>is "UniDOS".  It runs a Z-80 at 8 MHz.  How do these
>things communicate with DOS over the buss?  What is
>the software like?  How does one run CP/M on the Z80,
>or is that done??  In other words, how does CP/M on
>the co-processor access the PC hardware (disks)??
>The UniDOS device is on a half-card, and costs $175.
>
I have just such a co-processor board (the Baby Blue(tm?)), and
it works by placing the 64k of z80 memory somewhere in the memory space
of the PC (you get to select where using dip switches).  CP/M programs
have an MS/DOS header added which will find where the BB memory is and
copy the Z80 code (along with the BIOS/BDOS routines, more about them
later) up to the BB memory, and then releases the hold on the Z80
using an I/O port on the PC (also selectable, I think).  When the 
CP/M program wants to do I/O or whatever, the BIOS/BDOS emulation
routines set up info in a buffer (I think) and either set a flag
or use an I/O port to notify the PC that help is needed, at which 
point the PC does what is needed and then lets the Z80 run again.

On the Baby Blue, you prepare a CP/M program by adding the loader
to the .COM, and then you just run the program as though it were a
standard MS/DOS program.

Be sure that the UniDOS board will actually run on your PC when the
PC runs at the speed you wish it to.  My Baby Blue board is for sale
because it would not run fast enough to keep up with my AT. (8MHz BUS
Think about it... a Z80B is a 6MHz part.  Anybody with a PC or XT want
to buy a good Baby Blue board?)
       
(And I personally think $175 is too much. I only want $70 for mine!)
Hope this helped.  Anybody else have contrary info to mine?
Anybody have any idea how to get my Baby Blue board to work on my
AT?????
-----
Rusty Carruth  UUCP:{uunet,boulder}!cadnetix!rusty  DOMAIN: rusty@cadnetix.com
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