Re: Minimal CP-M SBC design

>
>Subject: Re: Minimal CP-M SBC design
>   From: Ethan Dicks <ethan.dicksusap.gov>
>   Date: Sun, 11 May 2008 13:01:31 +0000
>     To: "General Discussion: On-Topic and
Off-Topic Posts" <cctalkclassiccmp.org>
>     Cc: Generalicecube.southpole.usap.gov,
> On-Topic Posts Only <cctechclassiccmp.org>
>
>On Sun, May 11, 2008 at 08:23:13AM -0400, Dave McGuire
wrote:
>>   Well I wasn't talking about a diskless
system...only one in which 
>> CP/M itself was in ROM.
>
>I personally find the idea intriguing, and I am about to
cobble up
>a system from (nearly) scratch.  I used Kaypros and the
like, back
>in the day, and really won't miss floppies (not that
there's an FDC
>chip within 3000 miles I could slap on this thing,
anyway).
>
>I don't mind the idea of stuffing "the OS" in
ROM vs loading off
>of removable media since I doubt I'll want to upgrade. 
I want to
>run a few CP/M-80 programs, and that's about it.

NOte It's not OS in rom, it's Rom as floppy replacement. 
CP/M load 
process for floppy is a booter load system tracks to ram..
The rom 
appaorach is booter loads system from ROM to ram. and once
in ram 
you can overlay, alter, patch, extend as desired.


>> >I still don't have the hang of this
"vintage" thing yet, probably 
>> >because I'm vintage myself.  Please forgive my
density...
>> 
>>   I often suffer from the same problem.  I think
very few of us, even 
>> here, actually used stuff like CP/M and PDP-11s
when they were 
>> considered current technology.
>
>I was a kid when S-100 machines were "in",
but, as came up earlier
>in this thread, I did hit the Osborne/Kaypro CP/M era.

When I was an adult S100 was introduced.


>I consider myself quite fortunate that I've gotten to
program PDP-11s
>on two different jobs right at the tail end of their
heyday (I was 18-20
>at the time).  I also consider myself fortunate that I
was working at
>a place that supported VAX/BSD customers in addition to
our VAX/VMS
>customers, so I was able to pick up some UNIX skills
nearly 25 years
>ago.  When folks bandy about "All the World's a
VAX", it really means
>something to me (I learned C from K&R on an 11/750
running 4.1BSD, so
>I _know_ how easy it is to write non-portable code).
>
>I do run things inemulation, but I also enjoy running
things on real
>iron.  Right now, I have a modern Elf within reach, as
well as an
>SBC6120.  The SBC6120 boots off of CF... no floppies, no
1/3 HP rotating
>media, but there's still a real 12-bit processor on the
board.  I don't
>consider that emulation in the slightest, even if my
"disks" don't rotate.
>OTOH, I also have, at home, "real" PDP-8s with
real DEC-made disks; they
>just aren't so portable as to be worth hauling down
here.  Same goes for
>a CP/M machine - I'm working on something smaller than a
princess phone.
>Quite portable compared to an S-100 or an Osborne.

Bob's SBC6120 is as close or better than a real 8e for
playing with code.

That s the point too. Emulation you just cant pay with wires
or add 
a parallel port.

>Just my take on why I mix classic CPUs with modern
peripherals... runs
>the original software, weighs a lot less.

;) and it can be faster too.  A 64K z80 system that has a
32mb CF will do 
everthing the same as my S100 create with a Quantum
D540(32mb) hard disk
only it cant cause back pain, it's about as fast and the CF
based machine
can run on small batteries where the S100 crate can suck up
a APS 1000VA 
UPS in short order (that has two 12V 7AH gell cells or
~168WH of power).


Allison

>-ethan
>
>-- 
>Ethan Dicks, A-333-S     Current South Pole Weather at
11-May-2008 at 12:40 Z
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>
>Ethan.Dicksusap.gov            http://
penguincentral.com/penguincentral.html

On Sun, 2008-05-11 at 16:25 -0400, Allison wrote:

> Bob's SBC6120 is as close or better than a real 8e for
playing with code.
> 
> That s the point too. Emulation you just cant pay with
wires or add 
> a parallel port.

Aha, I disagree.  You can't get at the innards of the 6120
at all,
because it's a chip.  If you want to get at the innards of
an emulator
then you can, although how accurately the emulator models
the logic of
the -8 might be an issue (my emulator doesn't model it at
all, but
largely does its own thing).

Adding a parallel port is easy - you've got one on your PC. 
Work out
what you want to talk to the parallel port, and graft on a
bit of code
to do it.  Dead easy.

Need more ports, or a smart-ish peripheral?  Get one of
those
microcontroller boards with a USB device port and a bunch of
IO lines.
The Arduino Diecimila looks pretty good for this, although
having more
than one UART would be nice.  The UART talks to a generic
USB-to-Serial
chip (FTDI, for those interested) and you've got an
assortment of
digital IO, analogue input and PWM lines to play with, and a
bunch of
timers and things.  It presents to the PC as a serial port,
and you
program it in C.  I reckon with one of them and a bit of
interfacing
hardware (level shifters and latches, mainly) I could drive
most PDP-8
peripherals (if I had any).

Gordon