On Sun, 16 Dec 2018, Norbert Kehrer via cctalk wrote:
I have not tested it, but I suppose, that also the PX-8 and PX-4 used the
protocol,
because the protocol specification defines the following device numbers:
- HX-20: 0x20 (probably also used for the HC-20)
- PX-8: 0x22
- PX-4: 0x23
That is especially interesting.
It is probable that the HX-20 worked with the TF20 on a file level load
and save, but the PX-8 was likely to work on a sector level.
The HC-20s that I had were Japanese machines brought to USA for some
software develpment in Berkeley. HudsonSoft?
The HX20 never caught on very well in USA. It had a few dedicated
applications, such as CableTV configuration.
There was no technical documentation available.
I had a little bit of incomplete Japanese documentation.
During the time that I had some machines, the technical manual and
protocol specification were unavailable in USA.
I don't remember the disk format for the TF20 external drives, and
they were unavailable in USA. IIRC, the only sample disk that I had used
a form of the Microsoft "Stand-Alone BASIC", much closer to the NEC
variants than the Coco. (seek center directory, with short directory
entries that included a starting cluster number, and a linked list Granule
Allocation Table (similar to MS-DOS FAT, and early Mac disk format)
DSDD, with 16 256 byte sectors per track (320K)
The Epson Geneva PX-8 had an external 3.5" floppy available, and CP/M!
However, the PX-8 3.5" had 40 cylinders, with 67.5 tpi, instead of the
common 80 cylinder 135 tpi of other 3.5" disks.
Those 40 cylinder 3.5" drives are quite rare.
I don't know about the track width; for reading, a PC can simply look at
every other track. And formatting a virgin disk and writing to it should
work. But, there is a definite possibility that RE-writing a PX-8 disk
would result in one that the PX-8 couldn't handle (EXACTLY the same
problem as RE-writing a 40 track 5.25" disk with an 80 track 5.25" drive)
With appropriate format handling software on the PC, it should be
possible for a PC connected using your system to work with actual Epson
diskettes, and emulate the Epson external drives.
Thank you for creating this!
Now, I wish that I had been able to keep the HC-20s!
--
Grumpy Ol' Fred ci...@xenosoft.com
