Kaypro System disks?

On 7 Jul 2009 at 17:33, feldman.r at comcast.net wrote: > <quote>Both the Kaypro 2x,4,10 (DSDD) and Zorba 40 trk (DSDD) formats > have a peculiarity that prevents you from using a disk that is created > on the "native" computer.? In both cases, the only way to transfer > files is to first format a transfer disk in the Kaypro or Zorba format > using MEDIA MASTER and your computer.? Then use the Kaypro or Zorba > computer to transfer files from the "native" disks to the disk you > created with MEDIA MASTER.? Then using MEDIA MASTER, you can transfer > the files to any format you wish.

Well, yes and no. The Kaypro formats, at least in its non-Advent ROM incarnations, 10 512-byte sectors per track, leaving out the IDAM on each track. The NEC 765 and its derivatives go blind for a period after the index (the original 765 and 8272 are blind for longer than the later versions of the chip) long enough to avoid seeing the IDAM. The problem with the Kaypro is that there is no IDAM on Kaypro- formatted diskettes, so the IAM of the first sector isn't seen and only 9 sectors instead of 10 are visible to the 765. There are several ways around this. One, as mentioned, is to format the Kaypro diskette on the PC and write files to it, but that assumes that you still have the Kaypro around to write the files. Another commonly used method is to tweak the spindle speed a bit slower so that the first sector IAM just slips past the "window". Another is to isolate/disconnect the INDEX/ signal from the floppy drive so that it isn't seen at all and the 765 always has its eyes open.

Finally, one can replace the uPD765 with a uPD7265, which leaves out the IDAM nonsense and Kaypro disks will read just fine.