Re: A2 5.25" drive on a PC?

["Bryan Parkoff" <nospam@nospam.com>]

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message 
news:dlvhhj$jgj$1@theodyn.ncf.ca...
> Tim Haynes (timhaynes@alumni.NO.SPAM.PLEASE.uwaterloo.ca) writes:
>> We all know that a PC cannot read/write an A2 disk because of basic
>> MFM/GCR differences.
>>
>> What about the possibility of putting together a specialized cable that
>> would adapt a standard A2 5.25" drive to a PC's serial port?  The cable
>> would also have to pull power from somewhere - possibly from a molex
>> connector hooked into the PC's power supply?  And then we'd need some
>> specialized PC software to actually do the reading/writing.
>>
>> Does this seem at all feasible?  Any thoughts?
>
> I just thought of this last week, with the recent thread about reading
> Apple disks on a PC.
>
> But when I gave a quick glance for the disk controller manual, I couldn't
> find it.  So I didn't take a close look at the schematic.
>
> BUt it would be the parallel port that would likely be the useuable
> port, because various control lines are needed, and you have more control
> over the lines than with the serial port where it's all pretty fixed.
>
> The Apple II was a pretty limited system compared to current computers.
> There may have been a good reason to shift some of the work to the 
> controller
> card back then, while today there is bound to be enough computer power to
> handle just about anything.
>
> One would have to look over the controller schematic, figure out what's
> being done, and how to do that in software.  There may be no way to
> eliminate all the hardware; I think of those LS125 drivers that at the
> least may be needed (or something like that) to provide enough drive for
> the signals going to the actual drive.
>
> Given the simplicity of the original controller card, even if some of
> it was needed it wouldn't be much.
>
>   MIchael
>
Hello,

    I do know someone who they already wired Disk II Drive to parallel port. 
The problem is that 6502 CPU must be involved to manipulate Disk II Drive to 
capture bit by bit at 1MHz timing.  80x86 has minimum 8MHz which all 
instructions do not match to 6502 instructions using exact cycle by cycle.
    They tried to use x86 instructions to capture bit by bit through 
parallel port at exact timing, but they got the wrong data in the bit 
stream.  It would be better to build simple few chips like Disk II 
controller.  It can be installed in PCI slot or USB port.  Capture data in 
the bit stream per second would be the memory buffer so x86 instructions are 
able to capture memory buffer and transfer to the memory space.

Bryan Parkoff