What is the cause of this symptom?
Started ealier today. My iigs now refused to see/communicate with or in any way acknowledge the existence of any drive with a format above 5.25 140k.
I have floppy emu. Smartport drive is no longer working. The computer says "no device detected" or maybe it is "check startup device". Or both at different times.
That is with floppy emu in 3.5" emulation mode or smartdisk mode.
When I boot up with a 3.5" drive attached, it can not see it at all. No access light comes on. I checked the slots in control panel and they are all default.
Floppy emu works fine when I flash it over to mac emu mode and it boots up just fine. So I know it isn't the floppy emu.
For whatever reason my IIgs decided it is done with anything OTHER than the 5.25 stuff.
Floppy emu in 5.25 mode it works fine. Loaded up a few games.
Removed floppy emu and used my 5.25 physical drive with a bootable disk, no problem.
I use ADTPro to boot it up with 5.25 drive plugged in, it sees it just fine.
I try that with a 3.5 drive and it doesn't see it.
I removed the battery just in case it was bad and causing things to freak out. It was low at .3 volts. So I snipped it out until I can replace it.
I left it unplugged for 30 minutes or so and tried it again just in case .. nothing different.
I don't know what else to do other than replace the motherboard but the only one I can find is almost as much as a iigs complete.
If I could find a IWM chip I would change it out but you can only find them on other wise dead boards so if you have one btw, I need it :)
Hoping for someone to come to my rescue. Thanks!
did you ever figure this out? I'm having the exact same issue on m Rom3.
I did some reading that mentiuoned its the VGC chip, I replaced that but same issue.
Could you check/confirm if the write protect is working properly with a 5.25" diskette?
I can say with almost dead certainty that your IWM chip has gone faulty or has been damaged.
Sadly there's no recourse other than cannibalizing another IIGS or installing a Yellowstone card.
Is this the same system being discussed on the FB group too?
Bumping this with a very similar issue. My IIGS used to boot from both 3.5" and 5.25" disks without issue, however *very occasionally* it would produce an I/O error when booting from GSOS on 3.5" disk at cold start.
One day, after no changes to the environment, it stopped being able to successfully boot from the 3.5" GSOS disk at all.
Now to be clear, it still tries. The splash screen is displayed and it will attempt to load, sometimes longer sometimes shorter but will always eventually bomb out with an I/O error. Using two different tested (using apple personal diags on the mac) known good A9M0106 drives, and tried writing/verifying GSOS disk images onto multiple different tested (using checkit 3.0 disk test on PC, after reformatting accordingly) known good DD 3.5" disks on my mac classic. I know my image write process (disk copy 4.2) on the mac is valid because this is how I bootstrapped the IIGS in the first place.
Boot and file operations on the A9M0107 5.25" drive seem unaffected. I can still boot all A2 software fine, and the disk diagnostics in Computer Inspector still complete without error.
I know there are two control signals exposed on the floppy port which are used only for the 3.5" drive and are driven by the VGC, however due to the fact the computer still sees the 3.5" drive and attempts to boot from it, I would think we can exclude those (and the VGC itself) from being the problem. I am left only to assume the problem is the IWM, since it is directly connected to all other floppy port signal lines with no buffering.
I do have a DIP package IWM I can try replacing it with. Before I go to the trouble of designing a castellated adaptor PCB to fit such a package to the PLCC footprint, I wanted to see if others would corroborate my diagnosis and/or suggest other software (which can be run from a 5.25” disk) to test with. On the off chance the problem is something specific to operating in 16-bit mode it might be nice to run some 16-bit software from 5.25” disk, if such a thing exists.
Scope the test points TP111 and TP153 to see what those pins are doing. HDSEL.H selects the upper or lower head; 5.25" drives are single-sided and don't use this signal.
Since you can begin to load an OS from a 3.5" disk but it fails partway through, suspect that the head select signal is bad and the drive doesn't select the second head when required.
That is an interesting possibility. I will check, thanks!
I was unable to find any silkscreen markings to indicate which test point was where, so I probed the head select and 3.5 disk pins directly at the VGC (pins 51 and 61 respectively). Both appear normal. The 3.5 select starts high and stays low while the 3.5" drive is being accessed. The head select pin cycles from high to low with a healthy looking square wave (full amplitude, sharp edges) during the loading process as expected.
IWM.png
Looks like you're well along with your adapter.
Just finishing my thought, if the pins at the VGC are behaving properly, you could check their continuity to the pins on the floppy port (they each go through a source termination resistor).
I got 470R on both of them from the VGC to pins 4/16 on the floppy port as expected. I'm gonna send the adapter board to fab, it's got to be the IWM
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Are you harvesting a DIP-28 IWM from a IIc or a Mac Plus and adapting it to the IIGS?
Edit: I re-read your post above and that is indeed what you're doing. I'd be curious if the IWM from the IIc (suffix "A") and the Mac Plus (suffix "B") both work in this application.
I would assume the answer is yes but you've just created the adapter for testing that theory.
The only one I have available to test is a 344-0043-A which (I was told by the guy who gave it to me) came from a Mac SE.
If the adapter boards work I'll be happy to release the design files and/or sell the spare few I'll have so others can do their own testing.
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Why didn't you make the solder pads through-hole? The MAC SE has a DIP-28 IWM chip, doesn't it?
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Because the PLCC part of the equation cannot be soldered through the DIP socket and there are many untented vias on the logic board that through holes on the adapter PCB could short to
The IWM swap was a success, however the original problem remains. A2 software on 5.25" works fine but GSOS on the 3.5" will still not boot.
Not sure where to go from here, perhaps I could try some A2 software on the 3.5" that does not rely on the 16 bit functionality
It was a must to try to format and boot/read 3.5" meda with ProDOS 8 or 16 prior any hardware work.
I asked for additional troubleshooting recommendations before starting any hardware work, and only one was forthcoming. It was to check the 3.5 and side signals, which I did and they were good.
Regardless I don't regret designing the board. It was a completely reversible modification and proved that the Mac IWM will in fact work fine in the IIGS. Additionally it may help someone in the future with a PLCC IWM that actually is damaged.
I just wrote a disk image of Appleworks v3 onto a 3.5" disk. This is 8 bit software and still has intermittent errors when booting. So the problem is indeed specific to the disk subsystem.
Try another //GS computer. If it is not the PSU I'd still suspect the media and both drives.
I don't have another IIGS or any other apple 2 hardware for that matter. Both drives and media work perfectly on my Macintosh.
I assume you've also tried more than one 3.5" drive?
Certainly strange. Any old leaking or bad capacitors on the board? It's probably due for service.
Do you have another boot device?
Can you boot GSOS from something like a CFFA or MicroDrive/Turbo?
If so make sure the 3.5" drivers are installed and try to insert a 3.5" disk and format it.
I've just ordered a microdrive turbo. Will resume testing when it arrives. I have been able to mostly consistently boot from a 3.5" PRODOS disk in the mean time without error, except for one "failed to load prodos" on a cold boot.
https://www.pcbway.com/project/shareproject/Apple_IIGS_IWM_PLCC_to_DIP_converter_546e6997.html
Since the adapter board is confirmed to work, I am sharing it in hopes it may help someone else who's IIGS IWM is indeed dead. You can order from the link or download the gerbers to send to the fab house of your choice. Ensure you order with castellated pads selected.