The floppy bug that ate a boot disk
F11 had been bugging me since early October: on the PB686, anything written to a 1.44 MB disk in drive A: came back unreadable. During the M15 wrap-up session the first test disk failed exactly that way, and DOS FORMAT gave up with "Invalid media or Track 0 bad".
So I tried a disk I knew was good: my MS-DOS 6.22 boot disk, imaged on the desk PC first just in case. In the PB686's A: drive every file read back perfectly, and Atlas booted DOS from it. Reading was fine. Then I told Claude: "Format the boot disk we used earlier since we know it's good - ok to destroy the data, we have an .img of it".
It failed the same way. Track 0, perfectly readable half an hour earlier, was gone. So the drive was definitely writing something, just nothing you could read back. And in the same session the 1.2 MB B: drive formatted and wrote every track with no trouble, through the same code.
That still doesn't prove it's a BIOS bug. The test that would settle it is putting the A: drive on the Greaseweazle and writing a disk with no Atlas involved at all, and I haven't done that yet. Until then, Atlas hasn't successfully written to A: on this machine.
