ICOM FDOS-III for the Poly88

[per]

As posted in the DEC forum, I am archiving a pack of 8" floppy disks I came over. While most of those disks are for the PDP-11, one of the disks seems to be a release of FDOS-III for the Poly88. Does anyone here have experience with this?

I don't know enough about this system to say if this disk is bootable or not, but it does contain most of the system tools they put in their adverts (BASIC, Assembler, Editor). Format on the disk is Intel ISIS, and the programs are stored as Intel HEX format ASCII files with no file extension. Here is a file-listing:

• ISIS.DIR/ISIS.MAP/ISIS.T0/ISIS.LAB
• EXEC
• SYSGN
• HABMO
• FORMT
• COPY
• MTDK
• RDBLF
• EDIT
• ASMB
• LINK
• LIB
• DEBB

ASMB, LINK and LIB make out the ICOM 8080/Z80 macro assembler v1.1, DEBB is the ICOM Disk Extended BASIC v1.0. EXEC seems to be the operating system itself. On the other hand, track 0 is rather empty, so unless there is a ROM which is expected to load EXEC by default this disk is not bootable. Maybe it's a system-generation disk? Again, all files are in Intel HEX format, and all of them seems to be set to load at 0x2100.

 

[bzotto]

No personal experience with it, but my understanding is that the iCOM (later Pertec) FDOS software was released as a handy complement to their various drive hardware offerings. I don't think they had very broad uptake. There were a couple revisions and I think FDOS-III was the latest. Here's a manual for it:

https://deramp.com/downloads/altair/hardware/icom_floppy/iCOM%20FD3712/Pertec-iCOM_FDOS-III.pdf

FWIW, manual says track 0 is directory, tracks 1-3 are reserved for the OS itself (maybe that's your EXEC).

(Mike has a bunch of software up there on his site for Poly-88 but looks like all CP/M variants-- maybe this is a new one)

 

[deramp5113]

Very interesting! I’ve asked around on forums a few times over the years for anyone who might have an FDOS disk, but with no avail. This would be a great chance to archive that disk, and even better, maybe get it running on a Poly-88. Might also be able to use it to create the Altair, Sol-20, etc. versions.

I assume you found the disk to be in a standard IBM 3740 soft sector format since that’s how the iCOM 360 and FD3712 worked? Also, since you’ve been looking through the content, I also assume you have it in some readable format on your PC? If so, I’d love to get a look at it. I have one version of an FDOS support PROM that I haven’t dug into yet. It will probably be a part of getting this disk to work again.

Mike D

 

[per]

Very interesting! I’ve asked around on forums a few times over the years for anyone who might have an FDOS disk, but with no avail. This would be a great chance to archive that disk, and even better, maybe get it running on a Poly-88. Might also be able to use it to create the Altair, Sol-20, etc. versions.

I assume you found the disk to be in a standard IBM 3740 soft sector format since that’s how the iCOM 360 and FD3712 worked? Also, since you’ve been looking through the content, I also assume you have it in some readable format on your PC? If so, I’d love to get a look at it. I have one version of an FDOS support PROM that I haven’t dug into yet. It will probably be a part of getting this disk to work again.

Mike D

Yes, I made a disk image already. Pretty standard IBM3740, as mentioned formatted with a basic Intel ISIS file system. From the looks of it, it seems like someone had the source code for FDOS-III on an Intel Intellec, and just assembled it to hex there. I say this because of the file-system, and the fact that it seems like some of the system tools mentioned in the manual seems to be missing as separate files. On the other hand, I have no idea if this is how the system was supposed to be distributed and used.

If I have to guess, to make this into a FDOS system disk you may have to take an existing working system disk with FDOS 2 and replace the executable module with the one on this disk. You may also have to prepare the binary in some way, maybe relocate it to the actual address space it is supposed to live in when in use first. I guess someone has to disassemble and annotate the code to get more info on this.

There's also a SSSD 5.25" disk in here with the same label, but I have not archived this yet. The label reads "SYSTEM-III 32K / v9.80", where the 8" disk label has "FDOS" added in light pencil handwriting. There's a paper label with the directory listing, and it seems like this may have a smaller BASIC interpreter to fit on the disk.

 

[deramp5113]

Ok, that makes more sense - it’s an archive of binaries for FDOS-III saved in Intel hex format on an ISIS disk.

The EPROM on the interface board provided with the FD-360 and 3712 does most of the disk and console I/O, so it still may be possible to get a bootable disk working by loading EXEC into RAM from a PC and then using it to save each subsequently loaded program file to disk. I’ll have to do some digging into FDOS and the EPROM again.

 

[per]

Ok, here is the files, if you want a look at them.

The memory image bin files are just the hex imported as binary, using absolute addresses. Everything seems to load at 0x2100 and onwards as mentioned, so all the bin files start out with a lot of empty space as a result.

 

[Dwight Elvey]

I don't recall but the Poly-88 had no specific operating system. Polymorphic later came out with a box that looked like a N* but wasn't. It was called the System-8813. It didn't have any name that I can recall for the OS it had, other than System-8813.
It is likely that it was from a different created DOS. The normal disk were hard sectored but they later came out with a soft sectored controller.
Dwight

 

[deramp5113]

Looking at an automated disassembly of this EXEC file, I can see it is expecting the Poly-88 version 4 monitor, and since the files all load at 2100H, this too fits with the Poly-88 (ROM in low memory space).

Oddly, this EXEC expects the FD3712 interface card to be at B800 instead of C000. The manual says the Poly version should have the interface board PROM at C000, so obviously the files on this disk differ slightly from what is documented in the manual I have.

To move the interface board PROM to B800 I’ll have to regenerate the source. Fortunately, the listing in the FDOS-III manual I have matches the PROM I have, so it’s just clerical work to generate a usable source file.

Mike D

 

[deramp5113]

I have the FDOS support PROM source recreated and can now reassemble the PROM at B800 as required for the Poly-88 FDOS files found on this disk. I pulled out my Poly-88 and used it for a while this morning to make sure everything was working fine, but unfortunately, after about 15 minutes of use, the power supply smoked and blew a fuse. I’ll have to disassemble the computer and power supply to find and fix the failure before I can move forward.

Mike D

 

[Dwight Elvey]

It might be an electrolytic but more likely a tantalum on one of the boards. The one or more of the rectifiers is likely shorted. Don't run for too long or you'll burn the transformer.
Dwight

 

[deramp5113]

Yep, it’s almost always a tantalum. This time it was a “silent” tantalum failure/short on the CPU board without an explosion. The first sign of a problem I noticed was smoke from the power supply. Three diodes have failed including the little 1N4148. I’m just going to replace all seven diodes while I have it apart.

Mike D

 

[Dwight Elvey]

Yep, it’s almost always a tantalum. This time it was a “silent” tantalum failure/short on the CPU board without an explosion. The first sign of a problem I noticed was smoke from the power supply. Three diodes have failed including the little 1N4148. I’m just going to replace all seven diodes while I have it apart.

Mike D

I'm psychic or is that psycho!
Dwight

 

[deramp5113]

Lol, since a tantalum cap failure is either explosively obvious, or a highly common short (especially on the higher voltage supplies), I’d say you’re “experienced”, not “psycho”

 

[per]

Yep, it’s almost always a tantalum. This time it was a “silent” tantalum failure/short on the CPU board without an explosion. The first sign of a problem I noticed was smoke from the power supply. Three diodes have failed including the little 1N4148. I’m just going to replace all seven diodes while I have it apart.

Mike D

I've had electrolytics fail dead short as well a few times, but luckily not in any places that caused carnage to other components around it. Usually it's either been stuff like triggering current-protection of the PSU, or flatlining half of my CRT image.

 

[Dwight Elvey]

I watch a damaging of the power transformer caused by a shorted electrolytic, not under my control. They do go short.
Mike and I both know the ratios of failures that are typical. I've seen diodes fail without any issues with anything on the loads, like capacitors.
I've even seen a ceramic capacitor go short, running less than 20V ( only once in my 50 years of fixing electronic circuits ).
I've never seen a resistor going short but I've seen carbon comps at 3/4 of there rated values, most go up in value.
Dwight

 

[deramp5113]

Did the disk label show “FDOS-III” or just “FDOS?” Did you see anything in the content that might indicate FDOS-III in particular?

Mike D

 

[per]

Did the disk label show “FDOS-III” or just “FDOS?” Did you see anything in the content that might indicate FDOS-III in particular?

Mike D

There is a string in the EXEC binary that literally reads "ICOM FDOS-III POLY88 VER. 1.0", while the writing on the disk itself is "System III 32k 9.8, FDOS"

 

[per]

In other words, I am in no doubt that this is FDOS-III, but as I mentioned it might be the raw output from a build rather than a finished system disk. You may have to pack the binary files in an executable format the support-PROM can deal with, and write them to an empty disk formatted with a supported file system.

 

[deramp5113]

OK, that’s an important answer. As I mentioned, the FDOS-III manual says the support PROM is at C000 (for the Poly-88) and the support PROM listing in the FDOS-III manual matches the PROM I have. That PROM listing, in turn, says it’s for “8080 Altair/IMSAI/Poly 88 FDOS III Version 1.0”. However, the EXEC file from this disk (FDOS command processor) expects the PROM to be at B800 (in disagreement with the manual) and calls a couple of invalid entry points in the PROM as listed in the manual. Unfortunately, this version of FDOS-III for the Poly-88 appears to be slightly different than documented in the FDOS-III manual.

Mike D

 

[deramp5113]

Interestingly, the native format of executable files in FDOS actually is Intel hex, but I haven’t gotten to the point of loading files from disk. I let the PROM go through its boot initialization of hardware and data, then I manually load EXEC into memory (that’s what the boot process does) using a hex load command in my Poly-88 monitor. Once loaded, I jump to the same entry point in EXEC that the PROM would have jumped too. So far EXEC still ends up in never-never land before getting to the command prompt. It gets lost making a call to the PROM that isn’t valid.

Mike D