Downgrading iomega zip disk embedded driver

[squoril]

As many of you know the mac plus requires iomega driver 4.2 to work on a mac plus, newer doesn't work.
Ive also learned that mac formatted zip100 disks have a hidden partition with the embedded driver so it can be bootable,
You can use IomegaTools to low level format the disk which replaces this hidden driver with whatever version of Iomega tools you used
However IomegaTools 4.2 (not the 4.2 driver) will NOT run on a mac plus, its needs system 7 AND a Mac SE or newer for the 256K ROMs with more SCSI support.

I am in the unique spot of A. Having a mac plus and ONLY a mac plus B. having disks with newer driver versions than 4.2, C. not wanting to simply use an alternate method of making Plus bootable zip disks (HDT, silver lining, etc)

Ive done some digging and learned that at the disk level the hidden driver partition is possibly 400 blocks and begins with block 21 (Driver 5.0.3 installed on my disks went to block 250ish, observed using Sedit running on my Plus)


I need some help, right now i have no disks with embedded driver 4.2 or a way to run Iomegatools 4.2 to make one.
Is their someone who can initialise a zip with Iot4.2 and get me a hex dump of the drive from block 0 to 450 (or where ever it goes back to zeros after the driver payload) my goal is to make a tool to one click downgrade the driver on zip disks to 4.2 that runs on a plus.

thanks
-squoril

 

[CC_333]

Do you have access to the patched Apple HD SC Setup?

I discovered years ago that if you format a Zip disk using that, it will work without Iomega drivers at all.

I used several disks formatted this way, and they worked fantastically on any Mac that supports the standard Apple drivers (pretty much all of them). the only negative I can think of is that you lose the ability to eject them without having to either reboot or use a utility that can remount "ejected" (unmounted) hard drives.

Beyond that, if you want to keep the Iomega drivers, by all means get the 4.2 driver if you can. I think your idea of making your one-click tool is great for those who don't want to bother with technically unsupported drivers and use the official Iomega ones.

c

 

[Realitystorm]

I found the same as cc_333, if I only planned to used the Iomega zip drive as my boot drive, and therefore not change disks while the system is on, the patched Apple HD SC setup worked fine. The only benefit I found of using the official Iomega driver was when I wanted the Iomega icon, and I wanted to be able to eject the disk and swap in a different one while the system was on. I believe I did a trick where a I would boot from a Zip Drive, then copy the system file to a ram drive, and then activate that system file, I think it was control and click, or something similar. After I did that I could ejected the ZipDrive. Not something I have needed to use in over a decade.

 

[squoril]

Do you have access to the patched Apple HD SC Setup?

I discovered years ago that if you format a Zip disk using that, it will work without Iomega drivers at all.

I used several disks formatted this way, and they worked fantastically on any Mac that supports the standard Apple drivers (pretty much all of them). the only negative I can think of is that you lose the ability to eject them without having to either reboot or use a utility that can remount "ejected" (unmounted) hard drives.

Beyond that, if you want to keep the Iomega drivers, by all means get the 4.2 driver if you can. I think your idea of making your one-click tool is great for those who don't want to bother with technically unsupported drivers and use the official Iomega ones.

c

I used HDT 1.3.1 to burn the HDT generic driver onto a zip drive which made it bootable on a plus, very simple and easy to do. I have not tested the limitations but i do know System 7 wouldnt let me eject the boot/system zip so i will have to set up a second zip drive to be able to use a second zip disk, I would be curious if iomega drivers would let you or if that's a system 7 limitation.

 

[CC_333]

System 7 wouldnt let me eject the boot/system zip ... I would be curious if iomega drivers would let you or if that's a system 7 limitation.

I'm pretty sure it's a System 7 thing. If you attempt to eject any startup disk by dragging its icon to the Trash, System 7 will refuse and display this dialog:



Curiously, it will eject the disk if you choose Eject from the Special menu – at least it does in Mini vMac. Of course, if the ejected startup disk can't be reinserted, things will break. On real Macs, this behavior is probably limited to floppy disks (Mini vMac pretends that all disks are floppies, so the SSW tends to treat them as such) as a hold over from the days when Macs only had one or two floppy drives (one internal and one external) and no provisions for an internal hard disk (such as your Plus).

c

 

[squoril]

I'm pretty sure it's a System 7 thing. If you attempt to eject any startup disk by dragging its icon to the Trash, System 7 will refuse and display this dialog:

View attachment 97622

Curiously, it will eject the disk if you choose Eject from the Special menu – at least it does in Mini vMac. Of course, if the ejected startup disk can't be reinserted, things will break. On real Macs, this behavior is probably limited to floppy disks (Mini vMac pretends that all disks are floppies, so the SSW tends to treat them as such) as a hold over from the days when Macs only had one or two floppy drives (one internal and one external) and no provisions for an internal hard disk (such as your Plus).

c

That's the error i get, I dont remember which eject method ive tried, will report back later, the HDT driver makes it appear as a standard SCSI hard drive.

Run on ramble from here on --------
Some unrelated things i observed the driver on my zips was 5.0.3 and SCSI probe shows a version of B0.5-ish i remember the 5
Added an internal zip drive externally (Set ID 3 physically end of chain. termination off) to the external zip drives chain port (Set ID 6 physically center of chain. termination on) SCSI probe sees the ID 3 drive and shows version K.08 but wont mount a disk, Enabled its termination (which changed ID to 2 as i needed jumper) and It automounted the disk on system 7 start and i got a quick popup updating firmware or something, fast loading bar and was gone before i knew what happened, Im guessing this is the Iomega auto disk firmware update. However I had the iomega 4.2 driver in the extensions which let it mount so im not sure what it updated. I need to check if the SCSI probe version for any of the drives has changed or if it replaced the driver in the extensions folder. The disk continued working and i saw in Sedit that the Version number in the zip disk hidden driver partition was still 5.0.3

I now have backed up the hidden partitions of a virgin MAC100 zip disk with factory 5.0.3 embedded driver
All i need is a zip100 with the 4.2 hidden partition driver and i think i can downgrade a zip disk so its bootable on a mac plus, using the mac plus to do that.

one other oddity is this is a fresh install of os 7.1 and the installer clean up extension is crashing because it wants an FPU? (F-line error on crash)
So i removed that extension so it will boot so its not there 100% yet