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I know that the Commodore 1571 drive works perfectly well with a C64, since the 1571 will detect it is connected to a C64, and will enter 1541 emulation mode. After which, the 1571 just behaves as a 1541.

BUT, the 1571 is a much more capable drive. Enhanced capabilities beyond the 1541 that I'm aware of include:

  1. Double-sided disk support, doubling the drive's capacity.
  2. Can reliably access tracks 36-40, for even greater capacity.
  3. MFM support, so compatible with CP/M and MS-DOS floppies.
  4. High-speed serial ("Burst") mode for faster file access.
  5. Improved CBM-DOS 3.0 in the ROM.

Is it possible to use the 1571 with the C64 in a manner that can utilize these enhanced capabilities?

NOTE: I'm especially interested in software hacks that can make 1571 capabilities accessible. I know there is little support in the C64 firmware for the 1571 since it pre-dates that drive by many years.

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Reset to default
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Mode Selection and Switching

  • By default a 1571 always boots up in 1541-mode
  • when detecting the first burst (C128) transfer it switches automatic into 1571-mode.
  • OPEN 1,8,15,"U0>M1":CLOSE 1 will switch 'manual' into 1571-mode.
  • OPEN 1,8,15,"U0>M0":CLOSE 1 switches back to 1541-mode

Additional Features in 1541 Mode

While the 1571 behaves by default (or when switched) like a 1541, many of the additional features can be used as well. For example handling both sides of the drive:

  • Command "U0>H0" will select the first (lower, standard) head.
  • Command "U0>H1" will select the second (upper) head (*1).

Additional Tracks

The mentioned increased tracks are by default only available in MFM format.

Fast Transfer

Fast transfer can be used only with a modified/extended C64 Kernel/Fast-Loader - essentially behaving like a C128, thus using the automatic switch to 1571-mode. In fact, for next to everything but basic 1541 operations a modified handler is neccessary.

Back in the days, there has been a near endless amount of utilities and patches to do so - at least it seams like when looking into old German magazines like 64'er. One of the most ambitious might have been BDOS, to handle IBM compatible MFM floppies. It runs as well on the C64 with some simple add on hardware to support burst mode. See p.55 of June 1989 issue of 64'er. To my knowledge it was written by the well known Andre Fachat.

*1 - This still will not behave like a flipped disk on a 1541, as the direction isn't reversed.

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    you can't format a disk to use the extra space. You can however do some light filing to a 1541 to allow it to reach those extra sectors as well. It gets wedged seeking that far. Also it should be mentioned that the transfer speed isn't a limit of the 1541 drive. It's a limit of the c64. The fast load carts fix a bug in the system. On a stock c64 you will never get fast load out of a 1571 because the computer is the bottleneck.
    – John Lord
    Jan 16, 2020 at 5:21
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    It looks like the hardware mod to a C64 to enable burst is trivial, and the firmware patch is just a little more complicated. Thus making the highly desirable faster loading (around 5x faster than slow serial) possible with a C64/1571, but not much faster than the best fast loaders designed for C64/1541.
    – Brian H
    Jan 21, 2020 at 1:11
  • @BrianH Yes, you're right. It's hard to get past that without substantial modifications. It's still the same C64. Then again,double the disk storage and fast loading sounds like a good deal.
    – Raffzahn
    Jan 21, 2020 at 2:18

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