amiga floppy disk reading experience

On 06/11/2010 02:12 PM, Chuck Guzis wrote: The SMC 9216 and 9229 (and the Western Digital second-source) are actually quite good. They use a DPLL. The 9239 uses an even better DPLL. Some of the all-in-ones used an analog PLL (notably the 279x), some a DPLL. I've never had any trouble with them, so I think they're probably designed reasonably well. I would argue that it's some of the best engineering ever, bearing in mind that all engineering involves tradeoffs. (I would argue that the essence of engineering is knowing how to make the tradeoff of getting the best design for the constraints, including the manufacturing cost.) The GCR is being done at effectively the single-density flux-transition timing, so doing a simple state-machine data separator (which is better than a one-shot but not as good as a PLL) is actually adequate. For a small sector size, a one-byte checksum isn't that bad. No. You can't even run at 2 MHz. The accelerators all slow down to normal Apple II speed (effectively 1.023 MHz average) for disk access. The final disk controller Apple offered for the Apple II, the one that could handle the high-density 3.5" "Apple Superdrive" (not to be confused with their later DVD "Superdrive"), used an on-board 6502 core, running at 2 MHz IIRC. Eric