View Full Version : Any Cromemco owners/users out there?

September 25th, 2007, 09:27 PM
The title says it all.


September 25th, 2007, 10:13 PM
Well, when I owned a Vector Graphic, eventually all the internal cards became cromemco ones.

If I ever get my Northstar Horizon to boot successfully, I once again have a lot of Cromemco cards I can use. I just love their 4FDC controller. The Z80 cpu card is a winner also.

September 26th, 2007, 02:43 AM
Heh, what's that old saw about great minds (or fools)...

My main working Cromemco is in fact a Vector MZ filled with Cromemco
cards, 2 FDDs & a 150MB HD, with two external 20MB HDs and an 8" FDD.
Much quieter and easier to work on than any Cromemco box.

Also have another MZ the way it's supposed to be though...


September 26th, 2007, 05:15 PM
I have a system 1, but I don't have a boot disk. I am unsure the status, but it's a stock system. "powers up" as they say on Ebay. I have not spent too much time with it.

Here is a picture:


more pics:

September 26th, 2007, 06:58 PM

I think I have some Cromemco S-100 boards in my stash someplace. I know I have a Cromemco Dazzler in terrible shape needing some TLC to restore. That is on the TODO list as well.

Great system you have there!

Andrew Lynch

September 26th, 2007, 08:00 PM
thanks. I could use some software. I have not tried downloading from the web and porting over to it yet.

September 26th, 2007, 08:17 PM
Nice system, although a little noisy with all those fans; what's in it?

Dave Dunfield has boot disk images for several versions of CDOS
(Cromemco's CP/M workalike) on his site:


However, not all PCs are capable of recreating the disk from the image,
because Cromemco uses a dual-density format (track 0 is SD, the rest DD)
and some PCs can't do SD.

But Dave also has a utility to create a boot diskette from scratch via
the serial port (we both worked on that, but his works and mine didn't ;-)

In any case, it should come up in the RDOS monitor; hook up a terminal
(or a PC with a null-modem adapter/cable and a terminal program) to the
RS-232 port on the FDC floppy controller and hit a few RETURNs. It should
show you a memory test and try to boot; hit ESC and you should have access
to the RDOS monitor commands if everything's working.

Let me know if you need or want any help bringing it up; I've got a few
CS-1s myself, as well as a fair pile of boards & documentation.


September 26th, 2007, 08:20 PM
Oops, never mind what's in it; shoulda looked at the pictures first.


September 27th, 2007, 04:39 AM
thanks. I could use some software. I have not tried downloading from the web and porting over to it yet.

What sort of software are you looking for? I presume a Cromemco boot disk right? Probably another owner could make you a boot disk. Or if someone sends me a boot disk (they are the soft sector variety, right?) I could try to make a copy with my Catweasel. It handles SD/DD mixed disks with no problem, I think.

The Dave Dunfield tools are invaluable for making disks and backing up physical disks with images. Very useful for storing the backup images offline as well.


Andrew Lynch

October 15th, 2007, 04:02 AM
I still have a selection of boards, a Blitz Bus, a pair of FDD's and enough PSU bits to bring CDOS and Cromix on line. Now all I need is a chassis and an IMI hard drive.

@billdeg: if you care to send me a couple of DSDD soft-sectored floppies I will gladly make you a CDOS boot disk. You can email me at james AT attfield dot CO dot UK if you want to take this further.


October 25th, 2007, 03:33 PM
96K? Unusual for a Cromemco, unless it's got 3rd party boards in it; they were usually multiples of 64K.

And if that's a *System* 3, you'd better take someone along; they ain't light!

Have fun!

October 25th, 2007, 11:07 PM
If it's only got *one* 8" drive you're lucky; it'll probably be a Tandon (and you may well also have a hard disk in there). Now if it had *two* (or four) then that'd probably be a dual Persci (two drives, one motor) - nice and fast, but not the most reliable (and I wouldn't want to repair one), and they generally pre-date the hard disk models.

Good luck and keep us posted.

October 26th, 2007, 02:46 PM
Today I picked up a donation consisting of a Cromemco System Three Model: CS3 S/N: 31856. The condition is excellent. There are no scratches, etc. The system came with a Cromemco desk (same as the brochure).

Hazletine 1510 - Appears to work, display is in great shape. Keyboard good, no burn-in or mold present. s/n: 213442-001 model: 4DTD155255

Texas Instruments 810 Printer and stand.
Very Good Cond.
part number 0994293-0002
s/n 04711 42035

NOTE: The three pieces of hardware were cabled together. I made notes so that I could cable the system back together when I got the system home. I am unsure the last time this system was last used. There appear to be backups as late as 1990.

THe system was in such nice shape that I decided to power it on after checking all of the cards and re-seat the chips on the cards. (ZPU, etc...the standard stuff that comes with the System Three.)

Drive A does not detect when a disk is inserted in the drive. Drive B does.

I have not been able to get to a RDOS (monitor) prompt either, following the directions from the manual.

TO DO: Get drive A to detect and read disks. OR swap drive A and B cable if possible.

October 26th, 2007, 05:45 PM
Sounds like one of the older systems after all, with a ZPU and 2 drives.

RDOS should wake up and test memory as soon as it sees a few C/Rs on the console and if you hit ESC you'll be in; if it doesn't, well, it could be almost anything. Terminal, cable, etc. or pretty well anything in the box.

I don't think you have separate A & B cables to swap; if you do then you have a most unusual system there... Shouldn't matter though; RDOS can boot from either drive, but if RDOS doesn't start you ain't gonna boot from any drive.

October 26th, 2007, 06:55 PM
As I learn more...
yes I could not swap the cables, it's the PerSci dual drive set up with just the one cable. Weird, must be a mechanical problem to explain why I can't get drive A to engage a disk..I have the system cabled up exactly like it was used, same equipment and cables. The drive mechanism working or not is pretty cool...when you insert the disk, a motor engages the head and holds the disk in place, no manual levers needed. When you push the "B" button (and there's an 8" disk in the drive) the motor pops the disk out again. Never used an S-100 system with that kind of luxury. Because drive B works mechanically, I get a the clue of what drive A should be doing at least.

If I was to guess, I'd say the drive is bad, or the controller card or both. Not the cables or processor card. I can't access RDOS, and I have the dip switch settings correctly set for both the processor card and the disk controller card - what would cause that? I can't rule out the terminal as a problem. I can type at it fine, but I will try it with another system to be sure.

There's just a little screen burn, but you don't notice it without the high-res photos I took.

I have some pics and will post them here, in a few minutes:

October 26th, 2007, 09:14 PM
Ah yes, PerScis; very nice drives as long as they work, but...
Tech manual on Bitsavers AFAIK; have fun!

Can't help much with RDOS not responding; could be anything. The only DIP switch on the FDC that'd matter is autoboot (which sets the baud rate to 300bpi) and there are no switches on the ZPU AFAIK aside from the speed toggle (4MHz). There are switches on the memory board(s) but it's not likely they'd be changed.

Any chance you didn't replace the cable from the back panel console connector to the FDC correctly when you put the cards back in?

What else is in there besides the ZPU BTW? 16FDC I suppose (or possibly a 4FDC) and probably a TUART and/or a PRI, but what else? How'd it get 96KB of memory (and why, I wonder - can't see how you'd use it)?

Good luck! If you think I can help, send me a PM & I can give you my phone#; a PITA to wait for email answers when you've got a question while deep in the guts of that fine system3.

One good thing; lots of excellent documentation and software around for Cromemco systems.

October 26th, 2007, 09:36 PM
There is one thing, although it's not very likely: Assuming that's a 16FDC in there, it has little chokes in series with the console I/O lines and a bad ground loop or static zap would sometimes open one of them.

If you don't find anything else, you might want to check those for continuity; they look like grey 1/4W resistors or might also look like tiny coils.

October 27th, 2007, 07:25 AM
I have the manuals fortunately. The drive card is a 4FDC. The other cards are the ZPU, 64KZ RAM card, and a PRI.

Maybe the monitor is a problem, I noticed that I can't get out of local mode, maybe the key is stuck.


October 27th, 2007, 03:59 PM
Umm, yeah, in local mode ya ain't gonna get a rise out of RDOS fer sure.

BTW, I saw your post on CCtalk about replacing the PerScis with Tandons; I could be wrong (as usual) but I don't think the 4FDC knows how to talk nice with Tandons and you'd have to move up to at least a 16FDC. But it sounds like you've got a pair of PerScis, so maybe swapping the drives would work; the C & D drives probably got a lot less wear & tear than the A drive. Even though you can boot from any drive it's still more convenient to be able to boot from A.

So I take it that it's only got 64K and not 96? That makes more sense.

I guess the sun came out?

October 28th, 2007, 06:17 AM
I am not going to replace the PerSci's with Tandon's. That IMHO would be a mistake. There must be a simpler solution. For now I will focus on RDOS and the terminal.

October 28th, 2007, 11:29 AM
A lot of old 8" drives, such as the SA800, used to have either a dip shunt or a set of staking pins on the drive logic board (usually near the connector) that designated what drive the unit was.

If you can find these, and change them one for the other, your operational drive would then become your first drive and vice versa.

October 28th, 2007, 12:18 PM
hmmm...maybe. Fortunately I have all of the documentation so I can diagnose what's what.

By weird coincidence, the class I am teaching Monday is about early disk drives, and we go into the PerSci drives a little.

The best next thing to do is carefully take pull out the drives and re-seat the drive controller chips and cables. Because this system was sitting in a temperature-controlled room, cabled up and ready to go since 1979, the connections may simply need a little giggling to restore full function. I don't think I need to make any dip switch changes, etc.

You have to have seen the house that this system came from...there was a room essentially dedicated to the System Three, and old books. Imagine "walking into 1979" - the view from the computer room was a window overlooking about 20 acres of woods; a really nice computer room.

October 28th, 2007, 02:57 PM
Well, I'd say the best next thing would be to be able to talk to RDOS ;-)
It'd be nice to be able to talk to the computer and verify that it's actually working (and that you have a good boot disk) before you start making changes to the configuration.

AFAIR assigning drive sequence is not quite the same as a "normal" Shugart or Tandon, but you've got the manual and in any case it would just require swapping the DS settings and drive locations.

Bill, I assume you got my phone # OK just in case?

October 29th, 2007, 08:04 PM
Thanks Mike for your help.

Here is an update:
RDOS works now. It probably always did, but the terminal was bad.
The Hazletine 1510 is stuck in local mode, I need to fix. I replaced with my trusty Zenith Z-19. I ran some memory dumps, and other RDOS monitor commands, seems perfectly functional.

There is nothing in the RDOS manual about changing the boot drive to B (PerSci dual drive), using a 4FDC with RDOS 1.1. There may be a hardware solution. If I find one, then I can bypass the bad A drive and boot with the B drive. At least I'd have one drive to play with.

I plan to remove the dual drive to see if there is a mechanical problem. The system definitely tries to boot from A, but the drive does not respond fully. The drive A light comes on and then the system hangs, RDOS hangs. If I am patient and careful, I can usually shake the drive loose.

I will keep you all posted.


October 29th, 2007, 10:09 PM
Diddo here! I have a 4FDC controller that works fine. I don't own any 8" drives so my first drive would be "C:". I too haven't figured out how to get it to try and boot from a different drive. I really don't want to get started with the 8" drives again. The 5.25 ones are enough of a pain, as it is. I thought I might have to come up with some kind of 8" terminator cable but haven't pursued that line of attack yet.

October 29th, 2007, 10:54 PM
Well, unlike later versions of RDOS it does look like the 4FDC version only boots from drive A.

But Chuck, are you sure about that drive C? Seems to me if you set the 5" drive jumper to A it should boot from that, no problem; it usually reads the drive type off the disk itself unless it's an IBM standard 8". The System 3 was the only one that had 8" disks (except for third-party stuff) so even the old 4FDC would have to be able to boot from a 5" floppy. Mind you, you'd probably have to gen a new version of CDOS.
Then again, I didn't do much with 4FDCs "in my day" other then scrap a few (and the systems they were in), so what do I know; 16FDCs could certainly boot from any drive and any size FWIW...

What kind of box i.e. which model have you got there?

October 30th, 2007, 01:10 AM

There's also the option of using 5 1/4" HD drives instead of the 8" drives; to the controller they're identical. Depending on the drive you'll probably have to change some jumpers and either install some jumpers on the FDC or make a custom cable to connect it to the 50-pin interface; a cheap and dirty way of tripling disk capacity in a 5" box or just replacing the 8" drives & disks with 5 1/4.

Of course you'll need an 8" drive initially (or 8" images) for the one-time conversion of your 8" disks.

October 30th, 2007, 09:06 AM
I got a couple of replies from cctalk, not sure if they are accurate, but..here is a summary of what I was told:

"... it appears that they use incandescent (!) bulbs for things like index pulse, etc. in those drives. "

"Disk detection on the Persci 270 series drives (and I think on the 299
series drives as well) is simply a microswitch triggered by the leading edge
of the diskette.

There are NO electronics in the insert detection / clamp / eject mechanism.
It is a trivial circuit consisting ONLY of a DC electric motor (24 volts, I
think) and 4 microswitches (two of these are operated by cams on the motor
shaft, one is the front panel eject switch and one is triggered by the
diskette itself when it's pushed in). All you need to troubleshoot it is a
multimeter. It has no connection to the actual "electronics" of the drive.
It's just straight DC electricity. Schematics are available on the Harte
site and in other places if you don't have the manuals.

The only thing different about the CS3 implementation is that they removed
the front bezel of the drives, and then replaced the eject switches that had
been part of the drive's own front bezel (now removed) with a switch on the
CS3 chassis. I don't remember if they connected this through the switch
wires left over from the (removed) Persci front bezel or if they did eject
through the 50-pin data interface connector (Persci did allow an eject
function through the 50-pin data cable)."

October 30th, 2007, 11:22 AM
Sounds good to me (of course I'd already read it ;-)

Which drives have you got in there BTW, 277s or 299Bs?

November 12th, 2007, 01:49 AM

A warm welcome to the cromemco community .

You need to get some initial life from your system so I would suggest
a) install minimum == cards floppy controller (4FDC), CPU (ZPU) and memory (64Kz)
b) Memory card configured so upon power up there is a hole in upper memory config to allow for BIOS on 4FDC which is at C000
c) ZPU has speed switch 2 or 4MHz so either should work
d) Serial cable from 4FDC serial port to an ascii terminal with no RS232 handshaking
e) Switches on the 4FDC to NOT select a baud rate
f) suggest connected ASCII terminal at 9600 baud

Upon power on ZPU should jump to C000 and upon you hitting enter a few times figure out the 9600 baud and print out an RDOS message

You say you have the manuals but if any are missing try my wesbite cards section


let me know how you are getting on

November 12th, 2007, 04:53 AM
refer to later posts for an update.

November 12th, 2007, 09:44 PM
Well, hello there; fancy meeting you here!

I've talked to Bill and last I heard he had RDOS running but was having trouble with the left PerSci (A & B). Am I correct in my understanding that RDOS 1.x as used on the 4FDC can only boot from drive A, and that he'll have to swap drives (or at least the DS jumper blocks)? I only have experience with 16 & 64FDC and RDOS 2 & 3.


November 13th, 2007, 05:45 AM
I have a modified 16FDC card from another system. I also have a TU ART card to play with. If I can't repair the PerSci, I will try to return the 16FDC back to "stock" and then use it to assign B as the boot drive, if that's possible. Anyone know for sure that this can be done? I don't have a copy of the 16FDC manual, but I am sure that it's easy to obtain online.

I have brought the whole system downstairs into my work area, and re-assembled the desk and installed the computer into the desk. I will put up pictures of the assembled system. Post 15 of this thread contains a link to the original pics I took, while the system was still in my living room.


November 13th, 2007, 03:15 PM
Hi Bill:

I would still recommend swapping drives or at least the Drive Select jumper blocks; if the 16FDC has been modified you're just adding another possible problem.

However, yes, the 16FDC with RDOS >=2.50 uses DIP switches 7 & 8 to determine the boot drive and you can also select it manually (Bx, where x=A to D); however, your CDOS should be version 2.45 or greater (and Cromix >= version 11.08 ).

You won't find this in the 16FDC manual AFAIK because it's a function of RDOS, and the relevant versions were released after the manual was printed.

Good luck!


November 15th, 2007, 08:53 AM

I've got a Z-2D: http://www.vintagecomputers.btinternet.co.uk/cpm/cromemco.htm

Big beast, works fine (once the old floppy drive was replaced). I have a CDOS boot disk (courtesy of a very kind UK collector), for my 4FDC based system.

I am looking for a CP/M boot disk for this set up, Dave Dunfield has an image on his site for a 16FDC based system. I know I ought to be be able to create one from scratch (starting from BDOS), but this is easier said than done and I much prefer to make / receive copies of boot disks rather than do it the hard way.


November 15th, 2007, 08:36 PM
Nice box, the Z-2; scrapped a couple 'cause they were kind of big and power hungry, but have regretted it a few times.

Have you actually tried Dave's image? I think it might well work with a 4FDC, but your problem would probably be the 8" format, although there are ways around that. There are others around as well, but they're 8" as well and may in fact be the same disk.

What's wrong with using CDOS? It's essentially a modified clone of CP/M after all.


November 26th, 2007, 07:33 PM
Update - I have swapped out the 4FDC and replaced with the 16FDC. With the added capability (more jumpers and RDOS upgrade) I can get the system to boot to the good B drive. Unfortunately the system software almost immediately re-directs to read from the A drive. Fair enough, at least I got a little farther.

I have some excellent info on PerSci repair. I continue to close in on a complete restoration and will work to fix the drive.

Of note: If you flash a bright light on the drive, you can get it to "eject" the disk even if there's none in the drive. Conversely you can trick it into thinking there's a disk in the drive when there really is not. I found this out by accident!


November 26th, 2007, 09:52 PM
Boy, you really don't want to swap those jumpers and bring it up on the second drive, do ya...

Alternately, you could disconnect the 8" drives and temporarily hook up a 5 1/4HD drive as drive A; needs a jumper from pin 34 to pin 22 (?) on the 50 pin connector.

Your CDOS is probably not new enough to run on B. Try a later version.


November 27th, 2007, 10:23 AM
Well strangely enough I have noticed that old versions of CDOS ... not only dont seem to support doubled sided and double density very clearly but also on booting head over to the A: drive.

In fact it will boot from B: completely then you would see the A: drive light power on.

Although you will find my versions of Cromemco CDOS on the web at this address (http://maben.homeip.net/static/S100/cromemco/code/operating%20systems/DOS%20CDOS/index.html)


It might be kind of difficult for you to get them from your Web / PC onto the cromemco system. (Er a whole disasterously large topic we could go on and on about). So if you contact me offline I suppose I could post you something from Swizerland if you got desperate!

regards marcus.

November 27th, 2007, 01:03 PM
I simply followed the directions in the manual for boot drive assignment, very easy. jumper switch 7 and 8 are used for this purpose, just like how one would assign a drive number to a Commdore 1571.

BTW CDOS 2.52 is the version I have.

November 27th, 2007, 11:35 PM
Ah, I misunderstood; CDOS _does_ boot and stay on drive B then; what software is it that switches to drive A?


November 27th, 2007, 11:41 PM
Well strangely enough I have noticed that old versions of CDOS ... not only dont seem to support doubled sided and double density very clearly but also on booting head over to the A: drive.
regards marcus.
Marcus: booting from other than drive A wasn't supported until CDOS 2.45 & Cromix 11.08.

See RDOS 2.50 Tech Note.


November 28th, 2007, 09:54 AM
It's an older version of CDOS that I assume thinks it's booting to the A drive. I need a newer version. (Anyone have a newer version of CDOS of 8" disk? I would be happy to mail a SASE to whomever can help).

In short, I theorize that:
1. there's a hardware AND software component to booting to any drive other than A.
2. You need to set the 16FDC to boot to an alternative drive, and it needs to have a new enough RDOS ROM to allow for this
3. once CDOS takes over, it needs to know to stay on the alternative drive.

Once I can get a newer version of CDOS, I can prove or disprove my theory.

December 20th, 2007, 02:13 PM
Formerly the Sysop of the "CrosNest RCPM-RBBS" (which ran on my Cromemco Z2D -- 24x7 from 1977-to-1997). First in Silicon Valley, California, then during my 15-yr stay in France. Foolishly, I left it behind.

Am looking for a replacement: ZPU, 16FDC, PRI, 64K, and chassis - complete!
If anyone knows where to acquire same... ???

December 25th, 2007, 02:46 AM
That pretty well sounds like a complete CDOS system (except for the FDD ;-)

What are these boxes worth these days? (especially to you ;-)