RX01 Floppies

Noel Chiappa jnc at mercury.lcs.mit.edu
Sun Nov 23 05:45:38 CST 2014

    > From: Johnny Billquist

    > The RX02 is not a standard double density floppy. It is a single
    > density format floppy with a double density encoding for the data area
    > of each sector. ..
    > I have double density IBM floppies at home, and believe me, I have
    > tried using them in RX01 and RX02 drives. 

Something I'm mildly curious about, all, knowing very little of the very-low
level recording techniques used in single-density, RX02, and 'standard'
double-density 8" floppies:

The RX02 documentation indicates that the encoding scheme used in the
double-density data portion of the sector is 'Modified Miller Code'. (Miller
Code I get - it's either 0 or 1 flux reversals per bit time, which is half the
maximum flux reversal rate used in the single-density FM encoding - but the
Modified Miller is beyond me; it's not explained very clearly, and I don't see
any value to forcing my aging neurons to work it out! :-)

So, my question: is either of those (Miller and Modified Miller) the same
recording scheme used in standard double-density, or do those use something
else again?


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