Re: 1571 images as G64

Date: Thu, 30 May 2013 18:31:00 +0200
Message-Id: <>
On 2013-05-30, at 00:51, Pete Rittwage wrote:

> Certainly you "could" do it.  I figured by the name of the extension and
> the intro to the document, that it was always just designed as an
> alternate/extension to the D64 format.  Calling it "G64" when used for
> 1571 or certainly Apple images makes less sense.  You could use the same
> format, though, just with a different signature.  GCR-1571, GCR-APL2, or
> whatever.

Yes, signature would be quite important in such case. While the type could possibly be derived from the number of tracks, giving a clear hint wouldn't hurt of course.

> On the Apple disk drive, they basically ripped out the Shugart board and
> made a simple circuit controlled by software, so you have direct software
> control over the actual field coils which move the heads.  While their
> "official" DOS only uses 35 tracks (0-34) like CBM,  it is possible to
> manipulate the heads to move not only 1/2 way in between tracks, but also
> 1/4.  It is still a wide head like the 1541, though, so it will destroy
> data for 1.5 tracks when you write.

Still interesting.. in CBM drives we can access half-tracks because the stepper is an 80 tracks one and the DOS moves it in double-steps. To move it in quarter-tracks would require different stepper I believe. Apart from this, if they need a special circuit to move it in quarter-tracks - does it make any sense when the non-modified drive can't access those anyway?

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Received on 2013-05-30 17:00:05

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