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Decmate II question

tradde

tradde

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Apr 30, 2003
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A good friend gave me a Decmate II awhile back. Appears the HD has gone bad. Been fiddling with it off and on to see if I could get it
to boot from the floppy drive. Disconnected the HD and once every so often the "Decmate II" screen shows up on the monitor. Thought
maybe having the HD controller still installed may be confusing it. So tonight I removed that. It will start to the "Decmate II" screen which
implies it passed all internal tests. My first question is should this screen stay on or just display for a bit and clear. It clears. Putting
a floppy in does nothing even though the manual says this is what I should do. So since I have never really used one of these before
I'd still like to boot it from floppy. I have plenty of floppy disks. The system even has the CP/M card installed. Any suggestions or tips
in what to try next? Thanks in advance.
Tim R
 
I've only had a couple of hours of time playing with one and that was a few weeks ago. The hard disk is ignored if it can't read or if the first 4 words read don't match what it expects. Then it tries to boot from the top floppy only. The drive select lamp should light and if it is having trouble reading it will display a large floppy disk on the screen using what I think are special graphic characters. You should hear the pressure pad load. I read through the boot code a couple of weeks ago and I am pretty sure it never tries the bottom drive.
Some things to keep in mind.
  • The drive select lights are in that curved center section of the drive on the left side. The top one is a little above center and the bottom one is a little below center.
  • If you want to write protect the diskette you need to cover the notch. I am not sure it will boot if protected or it may take a lot longer to do so.
  • The bottom diskette is inserted upside down. There is a cute arrow on official floppies that lines up with an arrow on the drive which you can see when the doors are open.
  • If you don't have the arrows, the top diskette is inserted with the write protect notch and sector hole on the left and the opening where the head touches the media goes in first. The plastic welds of the sleeve are on the bottom.
  • The floppy drive cable should be plugged into the connector closest to the floppy drive. There are two connectors for floppies in that opening in the right rear next to the power supply cable. The other one is for a machine equipped with a second RX50 instead of the hard disk.
I would double check that the power cable is plugged into the drive and that the interface cable goes to the correct connector on the motherboard. My hard disk also does not work although mine does spin up.

I can't be sure but I think the display blanks when it starts trying to boot. The drive select lamp comes on, the heads load, the spindle motor turns and you hear the heads seeking. If it is having trouble reading it will also go through a head homing operation. If everything is working it takes less time to boot from floppy than Windows or Linux does from a SSD.

I wish I had the APU (you called it the CPM board), which I think has a Z80 on it. That would be fun to play with. I have been keeping an eye out for one but I expect they are pretty rare.

Good luck!
 
Thanks, I knew most of that but it's good to confirm. My system would not go to the "Decmate II" screen if the HD was connected. Even when not connected but the controller installed it
would not. Possibly a defect on the controller. My DEC booklets that came with my system state to turn the machine on without a floppy installed. Let it boot to the "Decmate II" screen
and then install a floppy to have it boot. Yet, nothing happens if I do this. I do hear some floppy noise during the system test. I have even swapped in a known working RX50 from
my Rainbow-100 just to be sure it was not the floppy drive itself. It is possible I am not using a bootable disk, but would think it would be as it's labelled as a "system test" disk. Due to
the design of how the system boards fits it would be hard to do any checking of various signal directly.
 
Decided to continue to debug. I returned to using the Rainbow floppy as I know that works. If I have a floppy in the drive (that is labelled bootable) I hear some floppy noises but
it never fully boots. At the end is a flash in the middle of the screen then nothing on the screen. This may be where it's supposed to display an error code, but if it does it's too short
to read it. Not sure of where to go next. Sure would be nice if there were some debug LEDs lit to show what's wrong. Any ideas?
 
It seems like your biggest problem is the number of unknowns. You eliminated two of those by removing the hard disk and replacing the floppy drive with one that is known to work. I might also remove the APU (CPM board) just to make sure that is not causing some issue. The other unknown is the boot media. See if you can obtain a floppy known to boot. I was able to use PUTR and some Images I found on DBIT to make a bootable image. The image I used was called OS278WC. This at least boots although many of the utilities on it give an IMG ERR when I try to run them. But enough of it works that you can do a dir of the drive. We did have a WPS system disk that originally would boot but during attempts to make a copy of it we did something wrong and now it won't boot.

There appears to be a way to feed programs into the machine during boot over one of the serial ports. This was probably included for assembly line testing. I don't yet know how to do it but I mention it because I saw it in the boot rom when I was reading through the code.
 
DougIngraham said:
It seems like your biggest problem is the number of unknowns. You eliminated two of those by removing the hard disk and replacing the floppy drive with one that is known to work. I might also remove the APU (CPM board) just to make sure that is not causing some issue. The other unknown is the boot media. See if you can obtain a floppy known to boot. I was able to use PUTR and some Images I found on DBIT to make a bootable image. The image I used was called OS278WC. This at least boots although many of the utilities on it give an IMG ERR when I try to run them. But enough of it works that you can do a dir of the drive. We did have a WPS system disk that originally would boot but during attempts to make a copy of it we did something wrong and now it won't boot.

There appears to be a way to feed programs into the machine during boot over one of the serial ports. This was probably included for assembly line testing. I don't yet know how to do it but I mention it because I saw it in the boot rom when I was reading through the code.
Click to expand...
I plan to remove the CP/M board the next time I have the system board out. I have no way to make bootable media that I know of. I have many disks (included with the system) labelled bootable. I have to believe at least one really should boot. But of the several I have tried, none do. How did you make your bootable media? I have no system with a 5.25 inch drive
to even try. I don't know how I would get media to the Rainbow, and even if I did I don't know if that can make bootable media for the Decmate. Interesting comment about the serial port.
I have never read that, but it seems reasonable.
 
Aha, so now I know....

I have a number of DecMate floppy disks, long ago (1980s) my place of work had a typing pool that used DecMates and they often had faulty disks (so they said) and I asked them to give them to me. I planned to use the Tyvek wallets, but I'd always test the disks on a 360k PC drive and more than 50% would work fine (and they still work fine) so what the typists were trying to do with then I dread to think. I guess the DM is using a more 'difficult' format that the PC 360k one?

Anyway, many (most) have the red arrow stickers on them, and I always wondered what this was for. Now I know!! Thanks.

Geoff
 
CP/M board removed. No difference in trying to boot. Tried a few other "bootable" diskettes. About to put this on the back shelf for now.
 
I pulled an old DOS machine out of the closet that had a 3.5 inch drive. I located a 1.2 mb 5.25 inch floppy drive and installed it in the machine. Booted DOS from the 3.5" drive. I wrote PUTR and the disk images on my windows 10 box using a 3.5 inch USB drive I found in a box of odd stuff. You need to write the diskettes on a 1.2 mb floppy drive not because of the density but because the drive can do double the tracks. The RX50 is a single sided drive. You cant use the 1.2 mb media either. It must be the lower density media. Dysan called these 104 2D floppies. Single or double sided versions work.

The PUTR instructions are pretty clear for making images. I bulk erased my floppies before I wrote the images just to make certain nothing was on them. If there is a version of PUTR that would run under CPM then you should be able to write them on the Rainbow. Assuming the Rainbow has a hard drive to hold the image.

If you ever decide to sell the machine I am interested in that CPM card.

Best Wishes!
 
Wish I had an old DOS machine. I had an old Linux box I used for most of my pdp-11 stuff. Decided I no longer needed it and recycled it. Now wish I had kept it. Live and learn, must
be my motto. Any machine I have now won't have a floppy connector on the mobo. I have plenty of floppies for this if needed. I don't believe the Rainbow has the CP/M board. Never
used CP/M. The Rainbow does have a HD, but I don't know if it works either. These are very old drives and the long and bumpy drive back from Pa to Texas may have done them in.
 
I am pretty sure all three variants of the Rainbow have a Z-80 and could run CPM. The Z-80 is the processor that talks to the floppy drive on the Rainbow. You just need the CPM boot diskettes for it.
 
Yeah, I read up a bit on the Rainbow and this is true. As you can tell I know little about Decmates or Rainbows. I am more of a pdp-8 or pdp-11 person.
 
What type of floppy drive would I need to be able to create bootable media for this machine? Is a 360k floppy good enough or does it have to be a 1.2Mb drive? I don't have one of either in a PC right now but am looking for a machine that would be capable of creating said media. Thanks.
 
tradde said:
What type of floppy drive would I need to be able to create bootable media for this machine? Is a 360k floppy good enough or does it have to be a 1.2Mb drive? I don't have one of either in a PC right now but am looking for a machine that would be capable of creating said media. Thanks.
Click to expand...

I have the Decmate II as using the RX50 so you would need a 1.2MB (80 track) drive.
 
tradde said:
What type of floppy drive would I need to be able to create bootable media for this machine? Is a 360k floppy good enough or does it have to be a 1.2Mb drive? I don't have one of either in a PC right now but am looking for a machine that would be capable of creating said media. Thanks.
Click to expand...

You need a 1.2 mb drive. PUTR can read and write these floppies with a 1.2 mb drive under MSDOS. They are an unusual format. Here is a good writeup.

http://home.iae.nl/users/pb0aia/vax/rx50.html

In a nutshell, you need to use a 1.2 mb drive and you need to use double density (not quad density) media. The media can be single or double sided, that does not matter since the DEC format is single sided.

I dug out an old machine and put a 1.2 mb drive and a 1.44 mb drive on it and booted DOS and was able to write compatible floppies. It would have been slightly more convenient if I had a hard drive but it was not at all necessary. I used this arrangement because I have a 1.44 mb USB drive that works with win 10. If I remember correctly you can fit 3 RX-50 images on a 1.44 mb diskette.

Hope that helps.
 
That helps immensely. Thanks. I have several blank DEC 5.25 media. The problem is I don't have a system that is old enough to support a floppy drive. Got rid of the one I had before I got all these DEC machines. I now regret getting rid of it. I check eBay for systems from time to time but the prices for mostly untested machines is outrageous. Yeah, I check the posts here that list eBay and CL for items. So far I have not found a machine. I would like to find something local so it does not have to be shipped. Is there any PCI board or similar that would allow support of a floppy drive? I doubt it and would any OS support it.
 
Is there a certain era PC that first supported 5.25 1.2Mb drives? I don't wish to get something that won't support that. I have been Googling, but not easy to find that specific data.
 
Pretty much any desktop except the very earliest would support it. 80286 would be the earliest I would consider and an 80386 box should be a good choice. I suspect even the currently being made desktops probably have a floppy drive connector on the motherboard and windows would still support it. In that case it would just be a matter of finding a drive and cables. It would be something to look into if you are using a windows desktop. Even if Windows doesn't support it you can probably still boot MSDOS from floppy. It is also possible to find a USB to 5.25 inch 1.2 mb floppy adaptor but it seems unlikely that it would be able to support the unusual DEC format.
 
I would not expect to see a floppy connector in any current desktops. But I could be wrong. I build my own machines but have nothing very old. I know I would want at least a 386. Was never impressed with the 286. Had a Tatung 286 at Unisys long ago and it was a dog. Like you I doubt any USB floppy would work. I will do some looking.
 
By swapping the Decmate chassis with my Rainbow chassis I now have the Decmate coming up and displaying "Decmate II" on the monitor. Inserting a floppy appears to try to boot from it but never actually boots as far as I can tell. Just repeated floppy drive accesses while display a floppy picture then clearing.
 
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