Strange behavior with disks moved between PPC and 68k Macs

[MrFahrenheit]

I’ve been a Mac user since 1990, spanning system 6 through today’s OS X and everything inbetween. I know about drive extensions and blessing a system folder and HFS+. 
 

I have a Zip and a Jaz drive that I use for setting up, testing, and troubleshooting various Macs from a SE all the way to a 8600/300. I had set a bunch of them up on a Quadra running 7.6.1 and everything was great for past 5-6 months. 
 

A month ago I switched my Quadra out (that I use for imaging disks etc) with a 8600/300 running OS 9. I had some issues with freezing and such and as a result I think I had to format some of my disks and recopy the system software back onto them. I say I think because I know I did it to one disk but I don’t remember doing it to others. 
 

I’m smart enough to not format them HFS+. 
 

These disks load and mount just fine on any computer. You can see them and everything is good but last night suddenly all of my boot disks stopped working. I got flashing question mark. It was also at the same time as I put away my 8600/300 and pulled out my IIfx to test. Then I tried a IIci followed by an LC and an LC 475.  Nothing worked. I thought at first just Macs were bad, or the drives themselves were bad. 
 

I managed to get into my LC 475 running 7.6.1 and I copied the contents of one of my Jaz disks to the 475 drive and then I formatted the Jaz disk and copied it back. Rebooted and held down CMD-OPTION-SHIFT-DELETE and it booted!  So I tried another of my disks with 7.6.1. Flashing question mark. Did the same steps of copying the files off, formatting, and then copying back and it booted no problem. 
 

Back in the 90s I never used both a PPC and 68K Mac at the same time. When I upgraded to PPC I never went back. So I don’t have this experience. 
 

Is there something with formatting a drive on PPC Macs that makes them not bootable on 68k Macs?  If so, I may have classified some brand new hard drives I bought as dead because I set them up on a PPC and they wouldn’t boot a 68k. 
 

I seem to recall that Apple rewrote the SCSI manager somewhere along the line. Is that what is at play here ?  I guess I’m going to have to go back and copy all of my disks over and format them and copy back. 
 

It would seem a disk formatted on 68k boots a PPC Mac but not the other way around. Am I just going crazy and something else is going on here, or is this officially the reason?  I’ve searched but results from google only point at PPC to Intel issues. 

 

[Crutch]

Having just recently scrounged up some internal SCSI HDs I formatted with a PM 8100/80 back in 1994 and successfully connected them up to my SE/30 and booted from them in 2020, I can at least answer this part of your question definitively:  it is indeed possible to format a SCSI HD on a PPC Mac and have it boot properly on a 68k Mac.

Beyond that - I’m not sure what’s going on here!

 

[MrFahrenheit]

Having just recently scrounged up some internal SCSI HDs I formatted with a PM 8100/80 back in 1994 and successfully connected them up to my SE/30 and booted from them in 2020, I can at least answer this part of your question definitively:  it is indeed possible to format a SCSI HD on a PPC Mac and have it boot properly on a 68k Mac.

Beyond that - I’m not sure what’s going on here!

Ok. Weird. 
 

I’m going to try and narrow down the exact cause and update it here so that if anyone else ever has this issue they can find a solution on google. 

 

[MrFahrenheit]

I can confirm that all of my disks don’t work. Copying the data off of a disk, formatting it on a 68k Mac, and then copying the data back onto the disk allows it to boot. 
 

I don’t know what’s going on here but it’s definitely a mystery. 

 

[Papichulo]

this happend to me recently to. all a sudden none of my floppies were reading. i think onr of the floppy drives may of damaged the film . but some of the floppies could be formatted some not .weird

 

[LaPorta]

Now, which disks were failing to boot: the Zip or Jaz? Which machines were they not booting: all or only some? You were selecting the disk you wanted to boot from in the Startup Disk control panel? Were the disks being ejected at startup immediately, or were the machines reading from them for a while and then ejecting them? Are these internal or external drives? It sounds like a load order thing in that you using the command do ignore the internal drive made it load from whatever disk you had in.

The final thought I had is perhaps there is something with the later version of the Iomega Driver on the 8600 in OS 9 that is doing something fishy with the disks that prevents them from being bootable.

 

[cheesestraws]

I seem to recall that Apple rewrote the SCSI manager somewhere along the line. Is that what is at play here ?  I guess I’m going to have to go back and copy all of my disks over and format them and copy back. 

If I remember correctly, Iomega mucked about with the Zip driver at some point around that time; if you format the discs under the new driver, I believe they're not bootable.  If you format them as if they're a SCSI hard disc on a machine without the drivers on, I believe they will work to boot and be read/writeable on the newer machines.

 

[LaPorta]

If I remember correctly, Iomega mucked about with the Zip driver at some point around that time; if you format the discs under the new driver, I believe they're not bootable.  If you format them as if they're a SCSI hard disc on a machine without the drivers on, I believe they will work to boot and be read/writeable on the newer machines.

Pretty much what I was trying to say; you just said it in a much cleaner way!

 

[cheesestraws]

Pretty much what I was trying to say; you just said it in a much cleaner way!

Ahh, that'll teach me for skimming the replies, I'm duplicating other people's ideas

Pretty sure I had this issue with a Plus and a more recent PowerBook ages ago, when I was booting my Pluses off Zip disks.  I think I resolved it by just formatting the Zip discs as generic SCSI removable discs using a generic formatting tool.

 

[MrFahrenheit]

Now, which disks were failing to boot: the Zip or Jaz? Which machines were they not booting: all or only some? You were selecting the disk you wanted to boot from in the Startup Disk control panel? Were the disks being ejected at startup immediately, or were the machines reading from them for a while and then ejecting them? Are these internal or external drives? It sounds like a load order thing in that you using the command do ignore the internal drive made it load from whatever disk you had in.

The final thought I had is perhaps there is something with the later version of the Iomega Driver on the 8600 in OS 9 that is doing something fishy with the disks that prevents them from being bootable.

The issue I was having affected Zip and Jaz disks. In fact, I have since found it also affected hard drives that I formatted with FWB HDT 2.5.3 on the PPC Mac and would not boot a 68k Mac. 
 

These 3 different “disks” were not booting any 68K Mac that I have but did boot PPC Macs. 
 

I was using the same Iomega driver 5.0.3 under 7.6.1 to format my drives, but I did an Apple “Special Menu” Format Disk on the affected disks. No I didn’t choose HFS+, I chose the regular HFS. 

I tried several methods to boot the disks. The Zip and Jaz are external drives. Termination is an active terminator. Jaz is SCSI ID 6 and Zip is 5. Jaz is last on the bus with the terminator. The hard disks I tried were internal drives. ID0. 
 

I tried many methods of booting including Command-Option-Shift-Delete, setting the disk as a startup disk, nothing worked. 
 

Formatting the disks (including the hard disk) under 7.6.1 on a 68k allowed them to boot again on 68k. 

 

[MrFahrenheit]

If I remember correctly, Iomega mucked about with the Zip driver at some point around that time; if you format the discs under the new driver, I believe they're not bootable.  If you format them as if they're a SCSI hard disc on a machine without the drivers on, I believe they will work to boot and be read/writeable on the newer machines.

I am using Iomega driver 5.0.3 on System 7.6.1 to format the disks using the Tools app. Some of the disks were erased using the “Special Menu” format disk under OS 9 on PPC. 
 

One thing remains constant:  

I boot a 68K Mac with my Jaz disk running 7.6.1 and Iomega driver 5.0.3 and proceed to erase a Zip disk in the Tools app, put a System Folder on the Zip disk, I can boot a 68K Mac. Same goes the other way (boot zip erase Jaz). 
 

I can use these disks to boot a PPC Mac and 68k Mac interchangeably. If I boot a zip or Jaz on the PPC Mac and erase one, and install a system folder it boots fine on a PPC Mac but will not boot up a 68k Mac. Same drives, same system software installs, same Iomega driver. The system folders are copies from fresh installs. 
 

After I discovered this “issue” I realized this was also why a brand new hard disk (NOS I bought on eBay) worked fine on PPC but wouldn’t boot on a 68K. I initially thought the hard disk was bad and set it aside. 
 

Going back i reformatted it using FWB 2.5.3 on a 68K and sure enough it proceeded to boot just fine after.