![]() ![]() Not only is it fixed, but it's so fixed that the state machine and the CPU each take it as so implicit that the Disk II doesn't look for explicit signalling from the CPU for each new byte of output: it assumes it knows exactly when the CPU will produce them and just samples the data lines then, without inspection of the CPU's control lines. So when reading you will not be able to detect flux transitions at a greater precision than that. The state machine which effects the drive's PLL is tuned to the GCR bit rate, which is the same as that of single density FM recording. It was also explicitly limited in terms of density, and effectively limited in terms of potential encoding unless you had a much faster processor. The Disk II controller in its original is effectively limited to the Disk II because of the connections offered in particular it expects direct control of a four-phase stepper motor whereas the standard Shugart bus exposes only step and direction signals.
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