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Questions with Mac Plus

mloret

Well-known member
Hey folks. Just ordered a Macintosh Plus that is on it's way to my house. The floppy drive needs help so it's booting to the floppy disk with a "?". Question, I have a BMOW floppy emu and also a bluescsi. I'm trying to figure out which will be the best solution to get this thing running. Will both work?

Also it seems that the disk images that work on the floppy emu (".dsk") and different than the ones that work on the bluescis (".hda"). I'm a noob, can someone explain why that is?

Thank you for your help.
 

volvo242gt

Well-known member
Either one should work. The floppy emu uses the Apple II style disk images, hence the .dsk extension. I'll let someone else comment on the BlueSCSI images.

With respect to the floppy drive, Paolo B. over at tinkerdifferent posted a PDF file showing how to readjust the zero track sensor, which may be what it needs to get it reading floppies again. I'd probably go ahead and give it a good cleaning and lubrication, though.
 

mloret

Well-known member
I'm sure it's just original lube that has turned to rock but I'll have to see when it comes in. Thank you for the feedback! I'm learning!
 

dochilli

Well-known member
The bluescsi needs an internal SCSI connector, that the plus does not have. So you need a gender changer to connect it to the external SCSI connector. Could be this one:

The Plus has no TermPower, so perhaps you need an external power supply. If you install a diode on the plus LB you can solve this problem.

The floppyemu will work.
 

rjkucia

Well-known member
I believe the Floppy Emulator can also take HDA images, but I haven't used one so I'm not completely sure. BlueSCSI is cheaper though, and will likely be much faster on the SCSI bus instead of floppy.

Throwing in a suggestion for a RaSCSI - a little more complicated than a BlueSCSI, but has tons more features.
 

cheesestraws

Well-known member
I see the normal confusion about disk images is out again in this thread. To recap many past discussions:

  • The file extensions (hda, img, dsk, etc) are weird and arbitrary and don't match to reality. There's no such thing as an "HDA image" or a "DSK image" or anything like that. People use the file extensions apparently at random for all kinds of stuff. People are like that. I don't even know where ".hda" came from, but the actual contents of the file aren't anything new. It's just a new way to confuse people. So it goes.

  • Most disk emulators, whether they're emulating floppy disks or hard disks, prefer to use 'raw' disk images. These files just contain the bytes from the disk in the order they are in in the disk. The file is the same size as the disk. There is no header or checksum. These often have the file extension '.dsk' on OSes where that matters, but often also have '.img' and I've seen '.raw'. File extensions are meaningless.

  • Classic Mac originated disk images tend to be in DiskCopy 4.2 or DiskCopy 6 formats. Despite the names, these are two different file formats. DiskCopy 4.2 only officially supports floppy disk sized images. DiskCopy 6 images can be any size. The Floppy Emu supports DiskCopy 4.2 images. Many of these seem to be called '.img' files, but I've seen '.diskcopy', '.dc42', '.dsk' and '.dmg'. About the only thing I haven't seen here is '.raw', thank goodness.

  • What is inthose disk images can really be one of two things. This isn't anything to do with the disk image file format, but reflects that fact that on the Mac there are really two kinds of disk. It can either be a floppy-like image that is just a raw partition which relies on a driver built into the OS, or a hard disc like image with its own driver partition and partition table, which allows them to be bootable without a ROM driver.
    • Floppy images are obviously the former, as are HD20 images. This is why you need a prosthetic boot disk to boot from the HD20 on a machine before the 512ke, because there's no driver to tell the machine how to read the boot code from the HD20.
    • SCSI hard discs are the latter.
    • SCSI removables can be either, depending on how they were formatted. For example, a Zip disc that was set up as bootable using HD SC Setup or something will be formatted as if it's a hard disk. A Zip disk that was formatted with the iOmega utility and which needs the Zip extension to be loaded is formatted as if it's a floppy.
    • CDs are a screaming chaos; they can be either. To be bootable, again, they need to be laid out logically like a hard disc with the relevant driver(s). However, if someone has imaged a CD as a single partition, it will appear to work but it won't be bootable. This is why a lot of the OS CDs on the Garden are broken. To confuse the issue still further, some emulators will boot an OS directly from a partition without needing the driver on the disk at all. So it's easy to end up with an image that will boot in an emulator but not on real hardware. Argh.
    • This, tangentially, is why bootable CDs are in the weird position where if you boot from them they mount fine, but they need an extension to be mounted from inside a running OS. Once again, so it goes.
  • Things are even further confused by the fact that some disk emulators are now experimenting with being able to wrap a raw partition in a partition table at runtime. I'm not sure what problem this is actually trying to solve, though it would be quite a cool way to implement, say, USB sticks.

  • That the BlueSCSI people apparently can't tell the difference between a disk format and a disk image format surprises me not one jot.
 

LaPorta

Well-known member
As a side note, it irritates me when software in the garden I need is made into ".dsk" images (whatever they may truly be), that are unreadable by Disk Copy 4.2 or 6.x....and then further are unable to be processed by ShrinkWrap or the like. What the heck are these things, and what in the world can read them? Even further, what is the point of making these images if they cannot even be read or opened on the very hardware and software they were meant to be used on?
 

cheesestraws

Well-known member
What the heck are these things, and what in the world can read them

These are probably raw images, suitable for use on something like the floppy emu, or for copying back onto floppies with dd from a modern machine. There's a magic incantation I can't remember to use the diskutil command to convert them to DiskCopy even on fairly modern OS X releases. There's also a tool to do it bundled with LisaEm, iirc.
 

LaPorta

Well-known member
Interesting. So, my usual complaint of "why the heck is there no GUI to just make this work" stands :p. To the OP, I hope these things work out well for you!
 

mloret

Well-known member
I see the normal confusion about disk images is out again in this thread. To recap many past discussions:

  • The file extensions (hda, img, dsk, etc) are weird and arbitrary and don't match to reality. There's no such thing as an "HDA image" or a "DSK image" or anything like that. People use the file extensions apparently at random for all kinds of stuff. People are like that. I don't even know where ".hda" came from, but the actual contents of the file aren't anything new. It's just a new way to confuse people. So it goes.

  • Most disk emulators, whether they're emulating floppy disks or hard disks, prefer to use 'raw' disk images. These files just contain the bytes from the disk in the order they are in in the disk. The file is the same size as the disk. There is no header or checksum. These often have the file extension '.dsk' on OSes where that matters, but often also have '.img' and I've seen '.raw'. File extensions are meaningless.

  • Classic Mac originated disk images tend to be in DiskCopy 4.2 or DiskCopy 6 formats. Despite the names, these are two different file formats. DiskCopy 4.2 only officially supports floppy disk sized images. DiskCopy 6 images can be any size. The Floppy Emu supports DiskCopy 4.2 images. Many of these seem to be called '.img' files, but I've seen '.diskcopy', '.dc42', '.dsk' and '.dmg'. About the only thing I haven't seen here is '.raw', thank goodness.

  • What is inthose disk images can really be one of two things. This isn't anything to do with the disk image file format, but reflects that fact that on the Mac there are really two kinds of disk. It can either be a floppy-like image that is just a raw partition which relies on a driver built into the OS, or a hard disc like image with its own driver partition and partition table, which allows them to be bootable without a ROM driver.
    • Floppy images are obviously the former, as are HD20 images. This is why you need a prosthetic boot disk to boot from the HD20 on a machine before the 512ke, because there's no driver to tell the machine how to read the boot code from the HD20.
    • SCSI hard discs are the latter.
    • SCSI removables can be either, depending on how they were formatted. For example, a Zip disc that was set up as bootable using HD SC Setup or something will be formatted as if it's a hard disk. A Zip disk that was formatted with the iOmega utility and which needs the Zip extension to be loaded is formatted as if it's a floppy.
    • CDs are a screaming chaos; they can be either. To be bootable, again, they need to be laid out logically like a hard disc with the relevant driver(s). However, if someone has imaged a CD as a single partition, it will appear to work but it won't be bootable. This is why a lot of the OS CDs on the Garden are broken. To confuse the issue still further, some emulators will boot an OS directly from a partition without needing the driver on the disk at all. So it's easy to end up with an image that will boot in an emulator but not on real hardware. Argh.
    • This, tangentially, is why bootable CDs are in the weird position where if you boot from them they mount fine, but they need an extension to be mounted from inside a running OS. Once again, so it goes.
  • Things are even further confused by the fact that some disk emulators are now experimenting with being able to wrap a raw partition in a partition table at runtime. I'm not sure what problem this is actually trying to solve, though it would be quite a cool way to implement, say, USB sticks.

  • That the BlueSCSI people apparently can't tell the difference between a disk format and a disk image format surprises me not one jot.
Thank you for this. Noobs like me benefit from the education. :)
 

reallyrandy

Well-known member
I have found that Toast 5.2.1 reads a lot of images that no other software will mount. I downloaded some dsk, dmg, smi, etc. files that Stuffit, Shrinkwrap, Disk Copy 4.2 or 6.x just would not read, but Toast 5.2.1 opened them right up.
 

reallyrandy

Well-known member
Yep, I have a G3 233 that I use as a bridge Mac. It has Firewire, USB and SCSI. Usually I will transfer files from my modern Mac to a USB/Firewire drive via USB. Then transfer to the G3 via Firewire. I unstuff and mount and re-package all software and files in a more compatible format. I can then transfer to a Blue SCSI or SCSI2SD for all my other Macs.
 
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