Re: A2 5.25" drive on a PC?

["Bill Garber" <willy46pa@comcast.net>]

"josephoswaldgg@hotmail.com" <josephoswald@gmail.com> wrote in message 
1132764690.952421.302500@z14g2000cwz.googlegroups.com">news:1132764690.952421.302500@z14g2000cwz.googlegroups.com...
>
> sicklittlemonkey wrote:
>> This is a neat idea, and I don't think the 6502 is necessary or even
>> desirable
>> for this sort of device.
>>
>> > Sounds pretty much like an Apple II with a nibble copier in that 
>> > dongle.
>>
>> More like an Apple II drive card (AKA Woz Machine) and a driver on the
>> host
>> PC to interface it to an emulator. The WM could be implemented in
>> software
>> on a microcontroller with enough RAM (say 8 or 16k) to buffer a track
>> of nibbles
>> (plus some timing info to handle nonstandard disks).
>
> Yes but microcontrollers that support so much RAM in an efficient
> enough way to handle a whole-track buffer are pretty much on an equal
> level with a 6502, but with the disadvantage that the cycle timings are
> all different, so you have to redesign an RWTS routine that is
> equivalent to the 6502 version in order to support writing, except in a
> "track-at-once mode" or something. Implementing the woz machine state
> controller in software on a microcontroller is also going to be *very*
> tricky. The hardware version runs absolutely cycle-for-cycle
> predictably at a 2 MHz clock rate.

Being the read/write cycle for the drive itself is so tight,
I recommend dropping direct read/write completely.

> That pretty much means you are making a microcomputer roughly as
> powerful as the Apple II+Woz machine in your dongle, or giving up
> single-sector writes.

Giving up any direct access to the drive and file systems is
most advisable.

> For read-only purposes, you could basically dump the read pulses
> sampled at a 2 MHz rate or so, into a FIFO, then process it on the host
> PC.

Memory cost and size nowadays is such that reading the
entire disk to ram would be the way to go, then manipulate
the data in ram, and write it all back to a fresh disk or
formatting the one read (if it is not an original) and
you'll have something you can actually use efficiently.

Also, the best connection to the PC/Mac would be USB,
being that is the trend now. Serial, too slow, and
parallel, almost non-existant in newer machines, are
not feasible. A memory device attachment?, maybe, but,
the software would be very complex. These would be,
just a few, SD/MMC/CF, etc......... Or better maybe
would PCMCIA.

Bill Garber