So, you want to create a hard disk image of a really old Macintosh,
but you are having trouble finding the software? Well, from the looks
of it, maybe you simply will never find some already written software
for this particular use case. Back in the day, the vast majority of
Macintosh users transferred data by copying files between floppy
disks. The more Unix-like methodology of doing a dd and sending the
result over the network is a foreign one to Macintosh users,
especially among old world Macintosh computers.
So, on we go with the search. Surprise surprise, if you know where to look, you can find a treasure trove of documentation on the disk interface.
20190525/DuckDuckGo inside macintosh scsi disk driver
20190525/http://www.fenestrated.net/mirrors/Apple%20Technotes%20%28As%20of%202002%29/tn/tn1189.html
Inside Macintosh was purportedly all on the Internet, but you’re going to need the Internet Archive Wayback Machine in order to see it. As was typically the case in recent years, Apple has been deleting all Macintosh Classic information from their website.
20190525/https://web.archive.org/web/20000306231850/http://developer.apple.com/techpubs/mac/Devices/Devices-122.html
20190525/https://web.archive.org/web/20000229231834/http://developer.apple.com/techpubs/macos8/mac8.html
20190525/https://web.archive.org/web/20000414113920/http://developer.apple.com/techpubs/mac/Devices/Devices-2.html
My old versions of Inside Macintosh (from pagetable.com) are also pretty helpful too. Basically, once you’ve got the driver number figured out to access a SCSI disk, you just call this really simple and easy Toolbox routine where you specify the address of the block you want to read, and it will be placed inside a buffer. Then you can easily complete the rest of the job just by using the documented serial interface in the old Inside Macintosh books.
Now, here’s another surprise. Once upon a time, there was a physical hardware device named Catweasel that allowed you to read Macintosh-style floppy disks from a PC. Unfortunately, it appears to no longer be on the market. If you had it, then there was this fancy Windows software that allowed you to easily access the files within those floppy disks images too.
20190525/DuckDuckGo macintosh device manager scsi disk driver read
write sector
20190525/DuckDuckGo macintosh send scsi disk image over network
20190525/https://www.macdisk.com/disksen.php
20190525/https://www.macdisk.com/macimgen.php
20190525/https://www.macdisk.com/mden.php
20190525/DuckDuckGo Catweasel board
20190525/https://en.wikipedia.org/wiki/Individual_Computers_Catweasel