7 Jul
2009
7 Jul
'09
12:38 p.m.
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.
--Chuck