SOMETHING INTERESTING/CAUTION
When the HD20 INIT is used with System 2.0/Finder 4.1, something very interesting happens. Not only does it allow an MFS system to see an 800K disk and format it MFS, it also allows it to read an HFS formatted disk inserted into the 800K drive.
Normally with 64K ROMs under an MFS system, an HFS disk inserted would not be recognized by the system without the HD20 INIT installed and a dialogue box would appear asking if you wanted to initialize the disk. Surprisingly this configuration allows it to read HFS formatted disks. But since it doesn't know from HFS, the disk appears as if it's MFS, no extra pixels in the disk window header, so you can't tell them apart at all. And there's no telling what writing to an HFS formatted disk with an MFS only system would do to the disk. So be aware.
The same thing happens using pre-HFS systems with 128K ROMs, but I certainly didn't expect it to happen with the HD20 INIT that seemingly should not even work with a system and finder that aren't aware of it. This really sheds some light on what the HD20 actually tells the system when it loads.
When the HD20 INIT is used with System 2.0/Finder 4.1, something very interesting happens. Not only does it allow an MFS system to see an 800K disk and format it MFS, it also allows it to read an HFS formatted disk inserted into the 800K drive.
Normally with 64K ROMs under an MFS system, an HFS disk inserted would not be recognized by the system without the HD20 INIT installed and a dialogue box would appear asking if you wanted to initialize the disk. Surprisingly this configuration allows it to read HFS formatted disks. But since it doesn't know from HFS, the disk appears as if it's MFS, no extra pixels in the disk window header, so you can't tell them apart at all. And there's no telling what writing to an HFS formatted disk with an MFS only system would do to the disk. So be aware.
The same thing happens using pre-HFS systems with 128K ROMs, but I certainly didn't expect it to happen with the HD20 INIT that seemingly should not even work with a system and finder that aren't aware of it. This really sheds some light on what the HD20 actually tells the system when it loads.