flashx20 - Floppy and screen for the Epson HX-20

[Fred Cisin]

> On December 16, 2018 at 11:14 PM allison via cctalk <cctalk at classiccmp.org> wrote:
>>
>>> 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
>>>
>>>
>>>
>> PX-8!
>>
> A subject dear to me.  I still have the px-8 I bought new (borrowed the money from my sister) as a young man in 1984.  Alas, I could never afford the PF-10 disk drive.
>
>
>>> 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.

On Sun, 16 Dec 2018, Will Cooke via cctalk wrote:
> Somewhere in my searches I recall reading that the 3 1/2" drives used 
> the same format as the 5 1/4" ones.  Maybe 40 tracks of 16 256 byte 
> sectors.  Oddly, I believe that 2 tracks are "reserved for CP/M" even 
> though it is in ROM and not stored on disk.

It was not uncommon for CP/M disks to have "reserved" or "system" tracks, 
even when the particular disk was not a bootable "system" disk.

I don't remember for sure, and don't have convenient access to my 
materials, but 16 256 byte physical sectors makes sense.

The drive manual
http://electrickery.xs4all.nl/comp/px8/doc/PF-10Manual.pdf
SAYS 9 512 byte sectors, but that seems likely to be in error from a cut 
and paste boilerplate from a different machine, because the more specific 
information is all for "64 sectors", which means CP/M RECORDS or "logical 
sectors" of 128 bytes each.  THAT would be consistent with either 8 512 
byte PHYSICAL sectors, or 16 256 byte PHYSICAL sectors.

--
Grumpy Ol' Fred     		cisin at xenosoft.com