Later IBM PS/2 series is where they showed up in the real world, but didn't get a whole lot of penetration outside of that.

BitWrangler wrote on 2023-02-27, 03:56:

Later IBM PS/2 series is where they showed up in the real world, but didn't get a whole lot of penetration outside of that.

I see... So it was only used in few places... Personally I only saw some bootable CDs used 2.88MB floppy images, but 1.44MB is still more common.

Recently I've been trying to generate 2.88MB DOS bootable images of different variants that I could use with GRUB4DOS, and I ended up ruining quite a few image files in the process due to many programs unaware of 2.88MB disks and tried treating them as 1.44MB ones. The reason I'm using 2.88MB here is that I could store more programs and configurations on the image than using 1.44MB.

LSS10999 wrote on 2023-02-27, 06:28:

BitWrangler wrote on 2023-02-27, 03:56:

Later IBM PS/2 series is where they showed up in the real world, but didn't get a whole lot of penetration outside of that.

I see... So it was only used in few places... Personally I only saw some bootable CDs used 2.88MB floppy images, but 1.44MB is still more common.

Recently I've been trying to generate 2.88MB DOS bootable images of different variants that I could use with GRUB4DOS, and I ended up ruining quite a few image files in the process due to many programs unaware of 2.88MB disks and tried treating them as 1.44MB ones. The reason I'm using 2.88MB here is that I could store more programs and configurations on the image than using 1.44MB.

The 586 motherboard floppy controllers and BIOSes do support it, I think.
Those high-speed floppy controllers were also being used by cheap streamers (those that mount in a floppy bay).

For 720 KB/DD, a 250 KB/s floppy controller is sufficient (XT era);
For 1,44 MB/HD, a 500 KB/s floppy controller is sufficient (AT era).

Those very fast floppy streamer cards for ISA slot supported 1500 KB/s or so.
If a streamer was connected to a normal FDC, it still worked, albeit slower.

So a Super I/O or LPC bus version of a modern floppy controller shouldn't be any worse that the special card.

The problem is the 2,88 MB drive itself, maybe. It was virtually non available,
except for IBM PS/2 PCs with their strange floppy cables.

Perhaps the VirtualBox people simple never saw a real drive they could experiment with, not sure.

Jo22 wrote on 2023-02-27, 07:38:

The 586 motherboard floppy controllers and BIOSes do support it, I think. Those high-speed floppy controllers were also being us […]
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The 586 motherboard floppy controllers and BIOSes do support it, I think.
Those high-speed floppy controllers were also being used by cheap streamers (those that mount in a floppy bay).

For 720 KB/DD, a 250 KB/s floppy controller is sufficient (XT era);
For 1,44 MB/HD, a 500 KB/s floppy controller is sufficient (AT era).

Those very fast floppy streamer cards for ISA slot supported 1500 KB/s or so.
If a streamer was connected to a normal FDC, it still worked, albeit slower.

So a Super I/O or LPC bus version of a modern floppy controller shouldn't be any worse that the special card.

The problem is the 2,88 MB drive itself, maybe. It was virtually non available,
except for IBM PS/2 PCs with their strange floppy cables.

Perhaps the VirtualBox people simple never saw a real drive they could experiment with, not sure.

On many motherboards with a floppy disk connector you can always find the option for 2.88MB, but it'll only work if you have the right disk and drive.

I just did an experiment with VBox... it seems if you mount a 2.88 MB floppy on VM startup, its BIOS will actually set it as 2.88MB so you can see the option to format it as 2.88MB on system startup. Otherwise, there will only be the option to format it as 1.44MB or 720KB, and programs may incorrectly format the images as 1.44MB if inserted in this state.

Also, Quick Format does not appear to work on a VBox-preformatted 2.88MB disk, only full format is possible and I can still get 2.88MB after format. Good news is that images formatted this way can be quick formatted from this point on and will still be 2.88MB. Also, it seems I can also reformat a 2.88MB image that was previously (incorrectly) formatted into 1.44MB back into 2.88MB from Windows using full format.

So in overall... 2.88MB floppy images can be used with VBox, but these problems are present:
- A 2.88MB image file (regardless of actual size used by the filesystem) must be inserted before VM power up, or VBox will default into making the virtual floppy drive as 1.44MB.
- Regardless of whether the image is (FAT12) preformatted or not on its creation, Quick Format cannot be used unless the image has been formatted from inside the OS (Win9x) at least once.
- Some features, namely Windows 9x startup disk, cannot be created, regardless of format status. It seems to complain about the disk being write-protected, even though in reality it was not, and I can still write contents into it. It is still possible to transfer system files via SYS or using the Format dialog, however.

While the other two issues are minor, the first issue is important as by mounting especially a brand new floppy image prior to system power on, one would be required to press F12 on VM startup and manually choose the virtual hard disk to boot, or VBox will try to boot into the floppy image which is unwanted in most cases. You can change the default boot order in the VM settings' System tab if desired.

It would be better if VBox offered an GUI option to set the disk controller's default format when no images are mounted beforehand...