CP/M survey

[Allison]

>
>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