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Screwed up my IMS 8000

A

alan8086

Experienced Member
Joined
Oct 1, 2016
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331
Location
Burnley, UK
I should have left what's well enough alone...

I've spent the last few weeks trying to get my IMS 8000 to a point where I can format disks and successfully movcpm and sysgen a system disk copy.

I'd got as far as finding and replacing a number of logic ICs and 2114 RAM ICs so finally I can format disks. I was still getting garbage characters on the screen when trying to movcpm so I carried on testing...

I can't get to the A:> prompt now. The boot disk loads the IMS CP/M version stuff and just locks up:

WP_20190323_18_34_40_Pro_LI.jpg

I should have been happy with being able to format disks etc but no - I had to go further and find out why I can't movcpm without a load of garbage on the screen and the system locking up!

Once again, I've tested every IC on there. They are all socketed and I have an ABI ICT-24 logic chip tester. The few larger ICs like the cpu, 8255, 8253 that it won't test - I've substituted with known good ones.

Maybe my BIOS is chip rotting?
 
SteveH said:
Could your boot disk have become corrupt? Have you got another boot disk to try before assuming it's a hardware problem. Just a thought.
Click to expand...

I've got the original cp/m system disks and numerous copies of them - they all worked fine up until this point. Don't think its the disks :(
 
Chuck(G) said:
Could be, but not really my first guess--that would be that your disk controller is a bit wonky.
Click to expand...

I discovered I had an IC inserted the wrong way round in its socket. I've desocketed all 300 or so chips to test in my chip tester that many times, I've started making tedious mistakes.This was in the I/O board that has the Serial ICs / Parallel ICs and the BIOS IC. I've removed the chip and it tests fine but I wonder If I've damaged the EPROM? Time to make an adapter to go from 2708 to 28C16? I have a copy of the ROM from an owner of the same machine.

I cant think of another reason why this should have happened. I can test 95% of the ICs in this machine in my tester - bar a few buffer ICs it wont test and the bigger ay-3-1015d / 8255 and the CPU - I've tested every other chip and found no issues. Drives? Cabling? Null modem cable?

:( :( :(
 
Are you able to cobble up a boot disk, say in the first (boot) sector that might give you some insight into what's happening?

It could be something as simple as a multi-sector read going wrong.
 
Chuck(G) said:
Are you able to cobble up a boot disk, say in the first (boot) sector that might give you some insight into what's happening?

It could be something as simple as a multi-sector read going wrong.
Click to expand...

Possibly - with some guidance :rolleyes:

I have working boot disks - do you mean a special purpose boot disk that will have a diagnostic use? Other than my IMS 8000 unit, I can connect its drives to an old MS DOS Pentium PC via an FDADAP adapter if that is any use?

I do have an NEC APC also - not very CP/M 80 compatible but I've used its drives in the past to make working IMD boot disks for the IMS 8000.
 
Yes, like that. Although I've got IMS8000 floppies, I'm not familiar with the innards of the machine, so I'm not the one to turn to for diagnostics. Does the machine have any sort of a monitor ROM?
 
Chuck(G) said:
Yes, like that. Although I've got IMS8000 floppies, I'm not familiar with the innards of the machine, so I'm not the one to turn to for diagnostics. Does the machine have any sort of a monitor ROM?
Click to expand...

No, no monitor that I can see in the literature. Perhaps I could put some sort if diagnostics on a 28C16 EEPROM after making an adapter? The BIOS code is on the setup floppy as an .asm file. There is a section on customising a BIOS, perhaps customizing the first sectors of a floppy would be possible. A learning curve for me.

The only thing left is to swap out the remaining ICs my tester won't touch on the I/O board and the floppy controller

After that its make a 2708 to 28C16 adapter and try a fresh BIOS

Then, I'm not sure - get some diagnostic code in there somehow via a floppy as you say.
 
In monitors for 8085 and Z80 that I've coded, I've found it useful to be able to trigger and trap either a maskable or non-maskable interrupt. This lets you see exactly where the code is hanging up. I suspect that there are bus monitor boards out there for S100 that latch the address on the M1 cycle so you can see where the code is going, but I can't recall any offhand.
 
Hmm - I just connected the two shugart drives to my Imagedisk rig - the A: drive failed all the 300K TestFDC tests and the B: drive passed as usual. Normally they both pass...

A: Drive failure:

TESTFDC A Error.jpg

For 300k single density only, I get - Format Write Error (0) NoSector

Tried two different SSSD 3M disks.

passes the 500K tests fine.

Maybe an issue with a drive or the cable? I had previously swapped the drives round when they were in the IMS 8000 plus swapping the various jumper positions. Always got the same freeze at CP/M boot issue.

B: drive passes Ok:

TESTFDC B Passed.jpg

A: Drive seems to got through the IMD format process Ok - 26 sectors / 250kbps FM / Sector size 128

Also seems to Write my IMS Setup disk from an image I have saved Ok too. I doubt I will have time to see if it works in the IMS8000 - evening is drawing to a close...
 
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In 2009 there was a guy in Austrailia who was restoring an IMS 5000 machine, the boards in it were as follows:
64Kb Dynamic Ram Board IMS C00464
I/O Board IMS c00442
Z80 CPU Board IMS C00451
Floppy Control Board IMS C00431

I believe that this should match up with the boards in your system, except that you have RAM spread across multiple boards. The other difference is that the IMS 5000 used 5.25" disks. As part of the restoration process, he wrote a Monitor ROM for it. I will send you the files.
 
new_castle_j said:
In 2009 there was a guy in Austrailia who was restoring an IMS 5000 machine, the boards in it were as follows:
64Kb Dynamic Ram Board IMS C00464
I/O Board IMS c00442
Z80 CPU Board IMS C00451
Floppy Control Board IMS C00431

I believe that this should match up with the boards in your system, except that you have RAM spread across multiple boards. The other difference is that the IMS 5000 used 5.25" disks. As part of the restoration process, he wrote a Monitor ROM for it. I will send you the files.
Click to expand...

I know the story - remember reading it on Herb's retro technology site. Thanks for wanting to send the files!

I'll try and find it again and refresh my memory.
 
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Its getting odder now - I swapped the drives so B: is now A:, made all the jumper adjustments etc...

Same result on using the original IMS 32K CP/M disk and any copies of it.

However - If I use a movcpm / sysgen'ed CP/M disk that came with the machine, (has 64K written on it so I assume it was the original working copy) - I now get an A: - but no response to any keyboard input..

Also works with a IMD's copy of the above disk.

64K disk response.jpg64k Disks.jpg

I have a flashing cursor after A>

I can type DIR etc but pressing Enter results in no response.

I did swap the two UART chips round in the I/O board earlier?
 
That did make me wonder if your problem isn't with your console interface... but I figured that you knew how to test that one.

At any rate, for the single-density stuff, it's entirely possible that your "tweener" is incapable of FM encoding. Lots of PCs are--you should run the "testfdc" utility here to see exactly what your PC is capable of.
 
Chuck(G) said:
That did make me wonder if your problem isn't with your console interface... but I figured that you knew how to test that one.

At any rate, for the single-density stuff, it's entirely possible that your "tweener" is incapable of FM encoding. Lots of PCs are--you should run the "testfdc" utility here to see exactly what your PC is capable of.
Click to expand...

As I said above - I ran TestFDC on both drives, I've done so many times before. Normally both drives pass all the TestFDC tests.

I have an Adaptec AHA-1542 ISA SCSI card in my 'tweener' box. The floppy controller on it is FM capable - passes all TestFDC tests.

This 300k failure is new behaviour - Hopefully the issue is to do with the drives and not my IMS 8000. Would explain a lot considering I cant find much wrong with the thing!
 
Chuck(G) said:
So your A: drive is 1.2M, not 360K? Otherwise, there's no reason for 300Kb/sec to work on it.
Click to expand...

Both drives are 8" SS Shugart SA800-2 's I set the BIOS to 1.2MB for both in my Pentium 133 tweener box. I chose the adaptec ISA controller card as research suggested its FDC would pass all the low density/FM tests. All I know is that usually both drives pass all the TestFDC tests except for the ones it skips by default.
 
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