Cromemco (was Extracting CDOS and CP/M) files)
M H Stein
dm561 at torfree.net
Sun Oct 14 02:01:41 CDT 2007
Date: Fri, 12 Oct 2007 21:00:18 -0400
From: "Roy J. Tellason" <rtellason at verizon.net>
Subject: Re: Extracting CDOS and CP/M) files
>That's more than I've got in there. It's a ZPU, 64KB ram card, I *think*
>that 64FDC, and an I/O card, not real sure but I think maybe it's the
Your basic single-user CDOS system, although I suspect that's a 16FDC.
I assume it's a System 3, or perhaps a Z-2? Either way, lots of room in there
for expansion ;-)
>No CDOS handy, I'm not even sure what I got for disks with that box, though
>I did get some, the problem with the drive having done some physical damage
>to the one that was in it. Somewhere around here I have a box of 8"
>floppies, but that would include what came with this system and also what
>came with the Imsai, at least, plus probably some stuff that folks have
>sent my way over the years.
Dave D has various images on his excellent site - also see below. If you're
having trouble with the 8" drive(s) and haven't gotten around to making the cable
for a 3 1/2" substitute, add a 7812 or use an old PC supply and temporarily hook
up a 5 1/4" drive; the FDC handles both.
>I'm not sure if I even have CP/M specific to that box.
Several people have configured CP/M for the Cromemco configuration; Barry
Watzman for one, if I'm not mistaken.
>Mostly I was looking for what sort of hardware capabilities would be needed...
You've got the basic hardware except for a 7812 or equivalent for the 5.25
(and 3.5" if 12V - see below) drives; the rest is software ;-)
>> Any version of Cromix (Cromemco's early Z80 and 68000 pseudo-UNIX) can
>> read/write any version of CDOS or Cromix disk (floppies, that is; hard
>> disks are a different story).
>I'd love to get some info on that software, particularly if I can ever get my
>hands on a DPU card to stick in there.
If/when you do, it's certainly out there. Several sites have extensive collections
of Cromemco software and manuals; one of the most complete is Marcus' site:
(Also see Herb Johnson's & Howard Harte's sites).
To run Z80 Cromix, all you'd need is another 64K; to run 68K Cromix/+
you'd need at least a 68000 DPU and 256K would be nice.
>Around the time I got that box I remember trying for some info and being told
>that the company wasn't doing anything but making 68K boxes for some
>specialized applications any more.
In the last years they'd become part of Dynatech, who had been using Cromemco
boxes for their TV weather systems and didn't seem particularly interested
in the computer business beyond supporting their own applications (they
apparently also owned Fuzz-Buster BTW). The European company that's
still around today is Cromemco in name only, having moved into UNIX
software long ago.
>> Cromix+ and UNIX both read/write UNIX format disks; anything else that
>> Cromix+ could handle was transferred to UNIX via a shared HD partition.
>What's a "unix format disk"?
Actually their name is "Uniform style floppy" and it's a format compatible with
both Cromix and UNIX (and without the pesky SD first track or Disk ID).
>> Anything else would indeed require some custom programming; the FDC
>> controller cards were reasonably well documented.
>That's mostly what I was looking for, if the common FDC chips back in those
>days were likely to be sufficient to handle a wide variety of "stuff" out there.
Well, hard sector disks might still be a problem...
>> If the main CPU was a 680x0 instead of a Z80 then Z80 & CP/M software was
>> run either on a dual (Z80/68000) DPU card or, if there was only a 680x0 CPU
>> then it was run on the Z80 on an I/O card such as the IOP I/O processor or
>> the Octart 8-port RS-232 card, if available.
>I saw the sheet on the IOP in my book just now, but don't know about that
>other one. Why would they stick a processor on an 8-port serial card?
Not relevant or supported in single-user CDOS (which used ordinary TUART
4-port serial and PRI 2-port parallel cards), but running a multi-user sort-of-UNIX
on a 4MHz Z80 wasn't exactly blindingly fast, especially on the slow hard
disks of the day. If the main CPU also had to directly service all those UARTS
it probably would grind to a halt so they handled serial I/O with coprocessors
(IOP & Octart), which later could also run Z80 user software in between I/O
requests when there wasn't a Z80 on the main processor board any longer.
The IOP is only the I/O *processor* BTW; there can be up to 4 installed, and each
can control up to 4 Quadart 4-port serial cards for a maximum of 16 ports;
that'd keep a single Z80 so busy it wouldn't have much time to actually
run those users' programs ;-). The Octart is a coprocessor and 8 ports combined,
and a system could have up to 4 for a total of 32 ports; although in practice
you wouldn't have that many users you could have I/O devices on all of
those ports (I have in fact had Cromemco systems installed with more than
32 terminals, although they were not all unique "users").
>> Their first hard disks were 11MB 8" IMI drives using a WDI controller; they
>> were superseded by 5 & 20 MB 5" IMI drives requiring a WDI-II. Then came
>> MFM disks using an STDC controller and SMD drives & controller, and finally
>> ESDI and SCSI drives using the ESDC controller.
>Rigging up some sort of mounting hardware and finding 12V power for some of
>the 3.5" HDs I have kicking around here should be an interesting
You'd need it for 5.25 drives for sure, but many 3.5" drives actually only require
5V which you already have for the 8" drive.
>I have nothing around for a controller, but given the choice I'd rather go
>with SCSI if possible.
SCSI wasn't supported until pretty late in the game and you'd need fairly
late versions of cards & OS; definitely not an option with your setup.
>> The floppy controller also supported the small tape drives while the larger
>> tapes required the ESDC controller, and there was also a controller and OS
>> support for 9-track mag tape.
Can't help any with the Bigboard, alas.
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