Internal floppy drive on iMac G3 - Firmware downgrade

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

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

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?

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....

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

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.

Awesome, thank you.

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

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)

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...

Intresting, will try that later, just trying to get my macbook to mount this fricking drive....

EDIT:

It is indeed disabled in the mac os rom, been playing with the mac os 8.1 HDD, if i use mac os rom 1.2, the drive dosen't work, if i use mac os rom 1.1.2, it works just fine.

just a pity 8.6 won't boot with 1.1.2

And a update, i have got the drive working in mac os 8.6

Using mac os rom 1.1.5 (rather than 1.1.2) did the trick

Very nice work! Are there any other public "Mac OS ROM" releases between 1.1.5 and 1.2? We could extract the ROM image from the file and try to find the difference between the last working version and the first nonworking version.

Edit: Looks like that's a negatory.

yep, seems 1.1.5 is the latest,

however i would like to try 1.2.1, since the 1.2 i used was from the Powermac G3 install disc, so may well be the reason the floppy isn't working in that version

And uniserver, did you try this yet? and if so did it work?

I'm guessing 1.2.1 won't work, but it's just a guess. 1.2.1 is from iMac Update 1.1, which was also released at the same time as iMac Firmware Update 1.0. I bet that's why people blamed the firmware update for disabling the floppy drive.

would make sense, i also wonder if people where just mixing up "iMac Firmware Update" and "iMac Update" because i must say, i initially thought the iMac update 1.1 was a firmware update.

Anyway, i'm pretty happy with the box booting 8.6, just got to finish off building it now just needs a floppy drive and hdd ordered for it...

This is very cool, can't wait to see the pics of the modded box.

Thanks

If you want to see the build process head over to macintosh garden and i have a thread over there on it, this is the second time i have done this mod, this time i'm trying to make the box a bit neater and with more features

Think i might mount up the floppy drive tommrow, will have to order my 8600 a new FDD and cable...

Cool, looks like i have another forum to join.

Topic link

http://macintoshgarden.org/forum/project-classic-mac-gameing-box-in-a-xbox-360-case?page=1

Very cool project max1zzz! I'll be watching that thread too.

I know you're satisfied with 8.6, but this whole mystery of the floppy support piqued my interest. I did some more digging and I think I see what happened. I decompressed several versions of the Mac OS ROM file (thanks to the SheepShaver source code)--1.1.2, 1.1.5, and 1.2. Starting with version 1.2, they removed the .Sony and .MFMFloppy DRVRs from the Mac OS ROM file. I still see their names referenced in places, but the actual DRVRs are no longer there. It didn't affect earlier machines with floppy drives because they use their built-in ROM which still has the floppy drivers, but it definitely affected the iMac.

It does kind of raise the question...would it be possible to bring support back to newer Mac OS versions by adding an extension that installs the .Sony and .MFMFloppy DRVRs on New World machines? The other possibility might be to patch the very newest Mac OS ROM file to include those drivers. Unfortunately, I am not well-versed in classic Mac driver voodoo, but I have to believe it's possible.

Yeah, would deffo be interesting to see if a way could be found to enable it on mac os 9, but i'm not sure how you would go about it. I would think trying to add them back to, say Mac os rom 3.0 (which came with 9.0) would be the best place to start

Well, I extracted the .Sony and .MFMFloppy drivers out of the Mac OS ROM file version 1.1.5. I'm pretty sure they're complete anyway...can't 100% guarantee it because I don't totally know how to parse the ROM resource list. Anyway, interestingly enough they appear to be written with 68k code rather than PowerPC.

I guess at some point we could try to figure out how to load drivers and see if loading them would re-enable the floppy drive in a newer OS version. Could probably be done from an extension or something rather than patching the Mac OS ROM file. It could also fail miserably though If you're ever interested in trying it, let me know and I can try to figure out how to manually load the drivers from an extension.

yeah, i would definatley be interested in trying to get the FDD working under os9, probably gonna stick 2 20gb hdd's in the box (or maybe 2 16gb cf cards) so i have pleanty of experimenting space

If you implement it via an extension versus the ROM, would you still be able to boot from a Floppy?

Unless the iMacs have a similar floppy driver at the Open Firmware level, I doubt they ever were able to boot from that internal floppy port. The floppy driver that I have found is in the Mac OS ROM file, which would only be loaded from an existing boot drive. So there's no real advantage to putting it in Mac OS ROM as opposed to an extension--at least that's my working assumption.

I dunno if it's even possible to fit a system small enough on one anyway

http://macintoshgarden.org/forum/project-classic-mac-gameing-box-in-a-xbox-360-case

Click to expand...

Darn, and I passed a streetpie 360 on trash day :/

if you wanted to do something like this in a xbox case they can be picked up damn cheap, i won one on ebay for £4.50 once (RRoD Console, so entire caseing, metal cage, and the scrap logicboard)

Out of intrest, did anyone else try this? still a little unsure if the firmware "updater" did anything, or weather no one ever thought of trying a older os / mac os rom before

Although nobody else has chimed in yet, I'm 99.9% sure that the Mac OS ROM file is the culprit considering that several drivers are removed from it in the newer versions that don't work.

And now that I think about it some more, the floppy drive never would have been bootable -- because the Mac OS ROM file is too big to fit on a floppy!

max1zzz: if it isn't too much trouble, it would be useful if you could list the drivers when you're in 8.6 with the older Mac OS ROM that has your floppy drive enabled.

To do that: Download MacRelix, open it up, and in the command prompt type "drvr" (without the quotes). Then hit return, and it should give you a list of drivers. It would be very useful to get the list that it spits out. I'd particularly be interested in knowing if .Sony and .MFMFloppy are in the list. Then, if you did the same thing with a newer Mac OS ROM file that doesn't have the floppy enabled we could confirm whether something's missing from that list.

I'm suspecting .MFMFloppy is going to be present with the older Mac OS ROM and missing with the newer...and making an extension that contains and loads it may be all that's needed. Maybe.

will do tomorrow, presumably that will be the case

I did see some claims it was bootable, and i somhow managed to get the imac to seem to try to boot from the FDD (floppy icon on screen and it didn't boot from the hdd) no idea how i got it to do that. but of coarse you couldn't get os 8 on a floppy anyway.

Isn't the OS8 netboot disc an 7.5.5 modified boot disk to fit on a 1.44mbDD?

You're probably right -- I don't know of any OS 8 floppies. But no matter what, there's no way a New World Mac could boot from a floppy due to the Mac OS ROM file being too big. It's a moot point though, because the iMac was the only one that actually had a floppy port on the logic board