The Disk geometry between PC and Mac formatted High density Floppies are the same:
Density: high
Bytes Per Sector: 512
Sectors Per Track (Cylinders): 18
Number of Tracks Per Disk: 80
Number of Heads/Sides: 2
Total Space on Disk: 1440 KB
RPM of Media in drive: 300rpm
Signal Data Encoding on Media: MFM
The differences between PC and Mac formats are in anatomy of the disk data sectors, sector addressing, file mapping allocation tables, and directory structures. Since the controller of a USB Floppy Drive is built into the drive itself with a tiny micro-controller processor (like an Arduinos' Amtel Microcontroller) and not in the computer like a Mac's SWIM Chip, you are stuck with the limitations of the hardware itself to encode disks any other way. This micro-controller is programmed to read/write/format under PC DOS.
Thus if the dd command can supercede the USB Floppy Drive's Microcontroller's programing and put down sectors as it wants too, there will be problems on how that data is represented on the directory and the file mapping table. In this case, replicating Mac System/OS Sectors on a disk that is formatted as a DOS Disk.
Using the USB Drive, because it is programmed to only work on DOS/FAT 12 format, any floppy disk formatted on it will be PC DOS Formatted under FAT 12. Under this format, Macs with the SWIM Chip and a high density drive can not decode them to extract raw data for booting. In the very least it will load up the first (boot) sector, run the program on it and then crash, which is part of the problem here. It can read and write them only after the system is booted and only if various extensions like PC-Exchange are loaded in as part of the system.
Thus there are problems as stated on this thread. As I know - formatting a disk on OSX after 10.6 for Macintosh format is no longer allowed because MFS is no longer supported on these machines. MFS could be brought back by emulation but it will not be perfect and there will be problems still. OSX will still recognize PC DOS formatted disks however.
Plus you have other issues with PC/OSX file transfers to Mac System/OS which involves Lost File Headers. This is another matter within itself but it is part of this problem of working with New and Old systems users have to be aware of. In short, something is being lost in translation on both cases causing problems for the average Vintage Mac user
John, I know you as a UNIX Expert extraordinaire as this is what you work in and earn your money from so you need to know a lot more than the average user. I'm not at the level you are on that field but you know me as the expert I am. We clashed heads many times before and our friendship continues despite that - you are one hell of a cool character as a friend. So here we are clashing heads again. If UNIX (particularly OSX) can rewrite an entire PC Formatted disk into Mac System/OS disk by superceding the limitations of the USB Floppy Microcontroller through the 'dd' command, then things should be fine. But things are not fine and there are problems. That is why I'm saying it can't happen and one needs a 'middle machine' to bridge the two systems together. It is my belief and opinion that software is limited by what the hardware can do and this is where the problems are. The answer in my opinion is in having a 'middle machine' like a 1400c with a floppy drive module running System 7.
If its just a data floppy disk with files, then those files can be recovered with some work. But being a boot disk, things become that much harder, and will require a 'middle machine' to straighten things out. In this case the following must be done:
From OSX:
- Download what files are needed. For a Boot Floppy that is a system folder with the system files inside it; preferably compressed as a Zip or Sit file to preserve file headers.
- Insert Floppy Disk and format it. (This will make the disk PC Formatted and not Mac formatted)
- Copy files from the OSX storage systems to the floppy disk in the drive.
- Take the floppy disk to the 'Middle Machine'
From the 'Middle Machine':
- Insert floppy disk from OSX into the floppy drive.
- copy the file(s) on it; preferably if it was compressed.
* If the file(s) were compressed, expand them into a separate folder here. Check the files and their icons to make sure they are not corrupted or lost file headers. An icon that looks like a blank piece of paper means that the file header is lost in that file. You need to go back to the OSX machine and try again or use a program like "Utility Dog" in the 'middle machine' to restore the file headers if you know them.
- Remove the floppy disk from OSX and insert a new floppy disk.
- Format the floppy disk as a Macintosh Disk.
- Copy the expanded files/folder into the Mac formatted disk. If it is just a System Folder, drag in into the floppy disk icon.
* If it is a System Folder that was copied, open the folder on the floppy disk and look over the files to see if they are copied correctly, icons are as they should be and then close it. This act will "bless" the System Folder to be able to boot from the disk.
- Eject and take the disk to the system in question, ie: SE\30
From "SE\30"
- If it is a boot floppy disk, turn on system without the floppy disk.
- As soon as the screen is visible, insert the floppy disk and watch it boot the system.
Things should work out fine or with minimal issues from here.
Density: high
Bytes Per Sector: 512
Sectors Per Track (Cylinders): 18
Number of Tracks Per Disk: 80
Number of Heads/Sides: 2
Total Space on Disk: 1440 KB
RPM of Media in drive: 300rpm
Signal Data Encoding on Media: MFM
The differences between PC and Mac formats are in anatomy of the disk data sectors, sector addressing, file mapping allocation tables, and directory structures. Since the controller of a USB Floppy Drive is built into the drive itself with a tiny micro-controller processor (like an Arduinos' Amtel Microcontroller) and not in the computer like a Mac's SWIM Chip, you are stuck with the limitations of the hardware itself to encode disks any other way. This micro-controller is programmed to read/write/format under PC DOS.
Thus if the dd command can supercede the USB Floppy Drive's Microcontroller's programing and put down sectors as it wants too, there will be problems on how that data is represented on the directory and the file mapping table. In this case, replicating Mac System/OS Sectors on a disk that is formatted as a DOS Disk.
Using the USB Drive, because it is programmed to only work on DOS/FAT 12 format, any floppy disk formatted on it will be PC DOS Formatted under FAT 12. Under this format, Macs with the SWIM Chip and a high density drive can not decode them to extract raw data for booting. In the very least it will load up the first (boot) sector, run the program on it and then crash, which is part of the problem here. It can read and write them only after the system is booted and only if various extensions like PC-Exchange are loaded in as part of the system.
Thus there are problems as stated on this thread. As I know - formatting a disk on OSX after 10.6 for Macintosh format is no longer allowed because MFS is no longer supported on these machines. MFS could be brought back by emulation but it will not be perfect and there will be problems still. OSX will still recognize PC DOS formatted disks however.
Plus you have other issues with PC/OSX file transfers to Mac System/OS which involves Lost File Headers. This is another matter within itself but it is part of this problem of working with New and Old systems users have to be aware of. In short, something is being lost in translation on both cases causing problems for the average Vintage Mac user
John, I know you as a UNIX Expert extraordinaire as this is what you work in and earn your money from so you need to know a lot more than the average user. I'm not at the level you are on that field but you know me as the expert I am. We clashed heads many times before and our friendship continues despite that - you are one hell of a cool character as a friend. So here we are clashing heads again. If UNIX (particularly OSX) can rewrite an entire PC Formatted disk into Mac System/OS disk by superceding the limitations of the USB Floppy Microcontroller through the 'dd' command, then things should be fine. But things are not fine and there are problems. That is why I'm saying it can't happen and one needs a 'middle machine' to bridge the two systems together. It is my belief and opinion that software is limited by what the hardware can do and this is where the problems are. The answer in my opinion is in having a 'middle machine' like a 1400c with a floppy drive module running System 7.
If its just a data floppy disk with files, then those files can be recovered with some work. But being a boot disk, things become that much harder, and will require a 'middle machine' to straighten things out. In this case the following must be done:
From OSX:
- Download what files are needed. For a Boot Floppy that is a system folder with the system files inside it; preferably compressed as a Zip or Sit file to preserve file headers.
- Insert Floppy Disk and format it. (This will make the disk PC Formatted and not Mac formatted)
- Copy files from the OSX storage systems to the floppy disk in the drive.
- Take the floppy disk to the 'Middle Machine'
From the 'Middle Machine':
- Insert floppy disk from OSX into the floppy drive.
- copy the file(s) on it; preferably if it was compressed.
* If the file(s) were compressed, expand them into a separate folder here. Check the files and their icons to make sure they are not corrupted or lost file headers. An icon that looks like a blank piece of paper means that the file header is lost in that file. You need to go back to the OSX machine and try again or use a program like "Utility Dog" in the 'middle machine' to restore the file headers if you know them.
- Remove the floppy disk from OSX and insert a new floppy disk.
- Format the floppy disk as a Macintosh Disk.
- Copy the expanded files/folder into the Mac formatted disk. If it is just a System Folder, drag in into the floppy disk icon.
* If it is a System Folder that was copied, open the folder on the floppy disk and look over the files to see if they are copied correctly, icons are as they should be and then close it. This act will "bless" the System Folder to be able to boot from the disk.
- Eject and take the disk to the system in question, ie: SE\30
From "SE\30"
- If it is a boot floppy disk, turn on system without the floppy disk.
- As soon as the screen is visible, insert the floppy disk and watch it boot the system.
Things should work out fine or with minimal issues from here.
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