Ultimate FDC? (Was: IBM 6360 - Filesystem(ish) info?

Warner Losh imp at bsdimp.com
Wed Feb 20 17:40:07 CST 2019

On Tue, Feb 19, 2019 at 3:38 PM Chuck Guzis via cctalk <
cctalk at classiccmp.org> wrote:

> On 2/19/19 2:02 PM, Fred Cisin via cctalk wrote:
> > Ability to read MFM data with FM headers (RX50)
> It's not that simple.  There's the matter of "DEC MFM" which encodes a
> few bit patterns differently to avoid collision with FM headers.

The RX50's are MFM encoded. There's no FM anything on it, unless it's that
way on all MFM diskettes.

Other DEC diskettes may have done this, but RX50's are just higher track
density, but old pre IBM-AT data encoding rate diskettes.

At least on the Rainbow the floppy chip is kept in MFM mode all the time,
unless you've written something to hack it to read alien disks.


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