Subject: Re: CP/M survey
From: ard at p850ug1.demon.co.uk (Tony Duell)
Date: Thu, 19 Apr 2007 18:40:54 +0100 (BST)
To: cctalk at
classiccmp.org
just tell it what particular ICs you're using
and at what port addresses, and
away it goes? Or was it more complex than that, and realistically you'd have
to write your own comms / FDC driver which exposed some defined interface to
CP/M itself?
You had to write something called a CBIOS (Customised Basic Input Output
System IIRC). This was a set of routines to handle terminal I/O (and
printer, paper tape I/O if you wanted that), disk block read/write, and
so on. There's a manual giving the specs for these routines, how to get
CP/M onto the target machine, and so on. The original CP/M distibution
came with the source for a CBIOS for the Intel MDS800 (IIRC)m which you
could use as a starting point
I've never done it, but it ;ooks like quite a 'fun' thing to do for
suitable values of 'fun'. Of course if you bought a packaged machine to
run CP/M it came with a CBIOS written for that machine. And alas you
rarely got the soruce of that :-(
-tony
Trust me haveing done it more tha a few times it was fun or at least
interesting.
You did miss the third case, packaged machine and time for upgrade. In
that case sometime the existing BIOS was needed or not. Having sone more
than a few random integrations (S100 crates) usually you didn't have a
explict bios to match but did have similar or at least a pattern. Often
during S100 upgrades here the FDC was the item being upgraded or outright
replaced it was easier to start from scratch and build in features the
earlier bios neglected like buffered IO for serial lines or better
error messages.
Allison