Re: Converting .DSK images to 5.25" floppy (part 2)

[mjmahon@aol.com (Michael J. Mahon)]

Roy wrote:

>Michael J. Mahon wrote:
>> Phil Dumpster wrote:
>> 
>> 
>>>"Michael J. Mahon" wrote:
>>>
>>>
>>>>And if you think that transferring images at 19200 baud is a pain,
>>>>wait until you find out about the special hardware you'll need to
>>>>attach an Apple drive to a PC.  ;-)  Writing Apple II disks on a
>>>>PC is not possible without unusual hardware and software which
>>>>is much harder to find and use than ADT.
>>>
>>> Has anyone ever tried to build a bus converter to adapt the 62 pin 8 bit
>>>ISA
>>>bus to the peculiarities of the apple bus?  You would then be able to put a
>>>real
>>>disk II controller into an ISA machine and then be able to use it with some
>>>dedicated software that would emulate the apple operating system, at least
>as
>>>far as the disks were concerned.
>>>
>>> Seems to me the hardware would be trivial - the 64K memory space of the
>>>apple
>>>bus could be mapped into the D or E block of the ISA machine.  Slot select
>>>signals could be generated the same way they are on a real apple.  Only bus
>>>timing might be a little sticky but could be accounted for.
>> 
>> 
>> I went down this path a few years ago...  My first idea was to simply
>> interface a Disk ][ drive to the PC parallel port--it has enough inputs
>> and outputs to control the drive.  Then I discovered that, regardless
>> of the speed of the processor, the maximum sampling rate of a signal
>> on the parallel port is limited by the (often virtual) ISA bus to about
>> 500kHz--not fast enough to do direct head signal decoding (which
>> requires about 2MHz sampling).
>> 
>> Next idea was to interface a Disk ][ Controller card to the parallel
>> port, which could be done, but would require a couple of clocks to
>> be generated outside the PC, so a medium-sized box would be
>> required between the parallel port and the Disk ][, with external
>> power supply.
>> 
>> Both solutions would have required re-writing RWTS for the PC
>> (an amusing task except for the difficulty of getting tight real-time
>> control on the PC).
>> 
>> At this point I reevaluated the situation and noted that adapting a
>> Disk ][ Controller to the ISA bus would eliminate some parallel
>> port issues (but still have ISA timings) and the need for an external
>> power supply and box.
>> 
>> This still seems to be the "path of least resistance" for accessing
>> Apple II disks on a PC (I have no Catweasel experience, and that
>> community seems to have little interest in Apple II's).  It would
>> require some hardware hacking a PC and a PC version of RWTS
>> (with timing finessed, somehow...).  Since my primary interest
>> was _reading_ Apple II disks, I would have been willing to re-read
>> several times to get a track read--a way of tolerating the timing
>> glitches caused by interrupts in the PC/Windows environment.
>> 
>> The combined effects of my having access to other convenient
>> ways to get bits back and forth between my Apples and my PCs
>> and the obsolescence of the ISA bus have caused me to put
>> this on the "back burner".  ;-)
>> 
>> Maybe someone else will take a run at it...
>> 
>> -michael
>
>The TracKstar allows one to read and write Apple II Disk II disks in 
>Disk II drives which are attached to the TrackStar, which, of course, is 
>a II on a PC card. The TrackStar can also read and write to PC drives. 
>However, I don't think you can, in DOS/Windows, access the Disk II drives.

That's correct.  The TrackStar was implemented as its own "little world",
using the PC only as a host.  The PC disk formats used to store Apple II
disk images have not been successfully converted to Apple .dsk image
files, to my knowledge.  (The ability to convert in both directions would
make the TrackStar a much more useful Apple accessory, though still
inconvenient relative to PC file system sharing, which can apparently be
done with appropriate networking).

I have also not seen any definitive explanation of how to install a
TrackStar in a Pentium-based PC (of course it must have ISA slots).
I've been led to believe that some cacheing must be disabled, but
have no idea which caches, how to do it, or whether it would work
with a 700MHz Pentium III.  ;-(

-michael

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