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Re: Access real hard disks - or their images

Posted: Fri Mar 12, 2021 12:16 am
by adespoton
Everything said so far is true. What's confusing is that things can be limited by the following:
HFS vs HFS+ drive partition
OS version
Mac OS ROM

So as a result, under HFS, I believe you can actually address up to 4GB on a single partition. Unfortunately, most ROMs won't be able to boot off of anything above 2GB. And the OS version has to be able to format the partition and reference the data on it.

Bringing this back to BII, it of course uses virtual storage, and the data is referenced inside some sort of integer, and the ROM is in reality a patched one. As a result, it has its own limitations on what can be booted from and what can be addressed, totally separate from the capabilities of HFS or HFS+, AND totally separate from the OS version being used.

To address more than 4GB, you need a ROM that can do it, an OS that can do it, and a partition format that can do it. Same goes for the 2GB limit, and the 2GB bootable partition limit.

But if anyone wants to do an exhaustive test, I'd be interested in the results :D

The bit about data forks and resource forks is also key -- there's a separate maximum for each, as well as a max file limit imposed by the OS AND a max file limit imposed by the partition format. This is where 7.5.2 and later removed a lot of the limits at the OS level. But you still need the ROM and FS support.

Re: Access real hard disks - or their images

Posted: Fri Mar 12, 2021 8:11 am
by salaxi54
Question: are disk images interchangable between emulators? eg. Basilisk, Shapeshifter, vMac etc.

Re: Access real hard disks - or their images

Posted: Fri Mar 12, 2021 12:36 pm
by Ronald P. Regensburg
Mostly yes. Depends on the size and the formatting. Also depends on the System/MacOS version running in the emulator. As you can deduce from the above discussion, Mac OS Standard formatted and moderate size is the most compatible.

Re: Access real hard disks - or their images

Posted: Fri Mar 12, 2021 5:24 pm
by adespoton
And as I just posted in a different thread, Mini vMac treats the image as a floppy with an alternate serial identifier, so aliases will break. I seem to recall this is also true for CD images.