Re: usb disk controller to read c64 disks.

----- Original Message ----- 
From: "Marko Mäkelä" <msmakela@gmail.com>
To: <cbm-hackers@musoftware.de>
Sent: Wednesday, September 21, 2011 2:20 AM
Subject: Re: usb disk controller to read c64 disks.


> On Tue, Sep 20, 2011 at 11:11:38PM -0400, MikeS wrote:
>>>"...to be able to read a "flip disk" in a double sided mech, you would
>>>need to find one where you can hack the mechanics to allow seek to
>>>"track -4".
>>
>>It would also have to be able to rotate backwards... ;-)
>
> Not necessarily. If you copy the raw data in real time (and buffer more
> than one rotation worth of it), you should be able to decode the track
> image in software. GCR is decoded in software anyway, it is not a big
> fundamental difference.

Of course - note the ;-) smiley; as a matter of fact I think at least one of 
the many archiving solutions out there has provisions for doing exactly 
that.

In the same vein I think on most drives it'd be much easier to just move the
upper head to match the track of the lower one than to extend the seek range
below track 0.

But if not flipping the disks was important enough to justify dealing with
the offset tracks then why not provide an option to reverse the drive motor
while you're at it, maybe activated by the head select signal. I wouldn't
think either mod would be particularly difficult.

But I don't have that many disks and I'm not a mountaineer ;-)

m

******************************************************
>
>>I must be missing something: why are you trying to read the "flip side"
>>with the upper head instead of just flipping the disk (assuming the drive
>>doesn't mind the missing index) ?
>
> To save effort. Instead of having to insert and remove disks 2*N times,
> you would have to insert them only N times. It is left an exercise to the
> reader to estimate how big N has to be so that the effort invested in the
> modifications is justified.
>
> An alternative explanation is along the lines of "Why climb a mountain?
> Because it exists."
>
> Best regards,
>
> Marko
>
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