Yes, '81 was pretty late . . . CP/M-86 came out then, as did PC-DOS.
Within a few years, nobody wanted to be limited by the same systems they
coveted only a few years earlier. By '81, the Apple][ could be equipped
with a Z80 board, a "real" FDC (Sorrento Valley Associates ?) an 80x24
display, and a hard disk if you could afford it. I recently sold the
prototype of the original Apple HDC I made up in the spring of '81 together
with my first ST-506.
Those were the days . . . <sigh>
Today I can still run CP/M but at an effective clock rate of 83MHz on my
notebook . . . designing hardware involves thousands of lines of HDL, weeks
in front of a simulation, and when it's done, I can't even hook up an
instrument small and fast enough to inspect it because even our government
can't afford one. One has to design circuits with 25% overhead so they can
be inspected. Oh, well . . .
Dick
-----Original Message-----
From: Allison J Parent <allisonp_at_world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Thursday, May 27, 1999 8:54 PM
Subject: Re: Re[4]: Bringing up a CPM
><If you're writing your own, it might be well to keep in mind that the BIOS
><used in several late-generation CP/M systems used device drivers which
coul
>
>It was late generation in 1981! I started doing it then. CPM had a formal
>product called CP/M+ (CP/M3.0) to extend that idea.
>
><California Computer Systems (CCS) had a pretty nice boot process in which
><they loaded a skeletal BIOS in a 32K CP/M, since 32K was the smallest
memor
><in which they claimed they could run. It wrote that to the boot blocks,
>
>Actualy it was 20k for cpm2.2, as it was distributed as a 20k system that
>you would run movcpm on to get the xxK version you wanted.
>
><then, under the control of that skeletal system, they loaded a "full-size"
><(you get to define that!) CP/M and transfer control to it. It's pretty
><solid and makes the preparation of a bootable disk a straightforward if no
><a quick process.
>
>Yes and they were doing it a long time back, Compupro too. Kaypro was one
>of the few "boxed" system that had the rom mapped to get a large TPA.
>
><IIRC, the XEROX 820 used a swapped-in BIOS which lived in PROM and was
><mapped into the TPA during file transfers, or something on that order. If
>
>Classic.
>
><your machine can handle that, it saves on BIOS size, especially tables,
etc
><and, generally speaking, if the READ operations from the TPA are from
><temprorarily mapped-in PROMs, you can overwrite the TPA in the event you'r
><loading overlays, with complete impunity. That way your
blocking/deblockin
><buffer space can still reside in high memory.
>
>An IMSAI can neither handle that nor not handle that. The basic design
>had no rom! To do that you need a prom card with a little bit of hardware
>to map it with an IO port.
>
>The key here is to get a working system in whatever space... Why, it's the
>development platfrom for itself. Once you have it running and can poke and
>understand it the improvements will come.
>
>Allison
>
>
Received on Fri May 28 1999 - 00:07:33 BST