Internal floppy drive on iMac G3 - Firmware downgrade

[max1zzz]

sucess! imac g3 reading a 800kb floppy disc!

the odd thing, i don't think it downgraded the firmware....

gonna grab a second cpu card and see what happens.....

EDIT:

now, you know what. i think we just wasted allot of time....

new cpu card, boot into 8.1, floppy drive works

boot into 9.2.2, it dosen't....

firmware on the card is 1.2

however, i did forget to remove the updater from startup items, so it could have done something to the firmware on the card, but both report 3.0.f2....

 

[dougg3]

Hmm, nice find on the 'fmwr' resource!

I'm not sure why the progress bar doesn't come up...it probably means that something in the updater script failed and it decided not to try replacing the firmware. I think I saw that happen when I had a checksum wrong on my B&W G3 updater, but we haven't messed with the checksums so it's not installing for some other reason. For whatever reason, the Open Firmware script decided it couldn't update the firmware. Hmm. You did power it down, push the paper clip into the programmer's button, power it on, and wait for the long beep, right? Then it acts like it's going to update, but it reboots instead?

It's possible that the 1.2 firmware changed something and now the 1.0 firmware updater script doesn't know how to handle it. That would take more digging in, but since you have the floppy working, it's probably not worth it

I'm glad you got it working! Woohoo! I am not sure what possibly could have re-enabled the floppy drive though if the firmware didn't install. Maybe nobody ever bothered rebooting back into an older OS back in the day to see if that was part of the problem?

 

[max1zzz]

Part of the problem may be how the psu is wired for that imac, there is no soft power on, also it dosen't have and speakers, and seems it won't give the startup tones through the headphone socket, so it makes this kinda hard but what i did was:

run the updater, wait for the imac to power down

pull the power

hold the programmers button and plug the power back in

at which point it would sit at a white screen for a bit then reboot

if i kept holding the button it would go to open firmware, if i let go it would just boot normally and prompt the update failed.

i also tried not holding the button, and got the exact same result, and i tried without pulling the power after it shuts down, and got the same resulat

Who knows what made it work, maybe no one ever bothered trying a older version of the os, but i find that hard to believe... i did try a differen't cpu card, bur as i didn't remove the updater from startup items it could have done something to the firmware...

The only way to ever really know is if somone else trys it

it would be intesting to see if it is possible to re enable floppy support in os9, but i have no idea where to even start on that

 

[Bunsen]

Congratulations!

 

[max1zzz]

Thanks and I must thank you guys, especially dougg3, for their help with the firmware (although it turned out to be unnessery)

And I have just tried it under os 8.5 (after allot of fussing, kept freezing as soon as I started the installer...) and it is still working will try it under 8.6 tommrow, I suspect either it or 9.0 will break it

 

[dougg3]

Hey, no prob. I'm just glad you got it to work! It'll be good to know for future reference.

I would be really interested in figuring out what it takes to re-enable it. I wonder if we could diff the floppy disk driver between 8.5/8.6 or 8.6/9.0 (whichever breaks it). That would be *awesome* to figure out what to patch so 9.2.2 still had it enabled. You should definitely post your OS test results so we can get a good idea of where to look.

 

[markyb86]

can you post a pic of the floppy connector?

 

[max1zzz]

Yeah, gonna increment up one os version at a time and seeing which one breaks it

Would defo be cool to see if we could get the floppy drive working in os 9

Markyb86, I will post one first thing tommrow morning, just the iMac has been packed away again

 

[markyb86]

awesome, no hurry and thank you :approve:

 

[olePigeon]

I still think it may be a Firmware issue, because my USB floppy works in 9.2.2.

 

[dougg3]

The onboard floppy port would use a different communication method though; it's not a USB drive. It would be very possible for an OS to quit including support for the onboard iMac floppy port while still supporting USB floppy drives (and still supporting other Macs' onboard floppy drives too).

 

[max1zzz]

markyb86, is it just a pic of the connecter on the board you want? just about to go and put the imac together for more experimenting

 

[markyb86]

Yes that's what I was interested in, thank you

 

[uniserver]

alright i am going to have to rip apart a imac tray loader and solder on the floppy header and try it now

I've always wondered with the LC-II's they remove the second floppy header, would soldering one back on enable it?

 

[max1zzz]

Good luck, hope it works

And, i have just tried installing 8.6, and it broke floppy support, so make sure you have 8.5 or 8.1 to hand

And as promised markyb86, pics of the floppy connector on the board:

and something odd happend while testing today, seems the imac still has the old style icon for when it can't find a boot disc in it's firmware:

No idea how i got it to do that though....

 

[dougg3]

Interesting! So 8.6 broke it. (We can assume 8.5.1 probably still had it enabled?)

I wonder what changed between those operating systems. Does 8.6 still have an iMac System Enabler? I see that 8.5 appears to have System Enabler 462 for the iMac. It contains, among other things, a single driver called .Infra (presumably for the IrDA)

Could the Mac OS ROM file have changed (8.5 has version 1.1.5), and there's something in the newer one that disables the floppy? That would probably get my first guess for where the change occurred, but I wouldn't have the first clue about hacking that file. I was hoping maybe I'd find a DRVR resource called "iMacInternalFloppy" or something that had been removed in 8.6, but no such luck

 

[protocol7]

The ROM file could be the culprit. It'd be worth trying to replace it with the one from 8.5 or 8.5.1 and see what happens.

 

[markyb86]

Awesome, thank you.

I wonder what changes were made to the design to remove a floppy from the exterior as well....

 

[max1zzz]

replaceing it with the one from 8.5 (1.1.5) broke it (made it crash on boot), trying to track down some newer ones, gonna extract the one out the rev b install disc (which i believe is 1.2.1)

 

[dougg3]

Another crazy thought -- what about trying a newer Mac OS ROM (like the one that came with 8.6) with Mac OS 8.5? Does that still boot, and if so, does the floppy work? That might be a way to figure out if the ROM file contains the change.

It looks like the Mac OS ROM file starts out as an Open Firmware script and then contains an LZSS compressed ROM image that it decompresses. Decompressing the ROM image manually might allow us to look and see what all it contains...