On Tue, Jul 17, 2018 at 2:49 PM, Grant Taylor via cctalk < cctalk@classiccmp.org> wrote:
> I conceptually get that the GoTEK can't go any faster than the Floppy's > IDE (I thought floppy was a derivative of IDE.) bus can carry the data. IDE came much later and isn't very similar to the floppy interface. Here's more history of it than you probably wanted: IBM invented the 8-inch floppy drive and had a proprietary interface to it (discussed here recently). Memorex made plug-compatible drives, but the IBM interface did not become an industry standard. With IBM's earliest floppy drives (23FD "Minnow"), even the medium, rotation rate, data encoding, and index hole locations weren't compatible with what became the industry standard. Minnow was shipped to customers as part of IBM mainframes and control units as a read-only device to load microcode, though obviously internally IBM had equipment to write the disks. IBM redesigned it as the 33FD "Igar", and that did set an industry standard for the media format, but still did not standardize the electrical interface. The Shugart SA-900/901 drive standardized a 50-pin interface for eight-inch floppy drives. The Shugart SA-4000 series 14-inch winchester hard disk drives used a similar but not identical 50-pin interface. The SA-1000 series 8-inch winchester hard drives moved the data to a "radial" interface using separate connectors for each drive, while keeping the 50-pin interface for control and status. The SA-4000 and SA-1000 series established defacto standards for early winchester drives. Shugart invented the 5.25-inch floppy drive. The Shugart SA-400 drive standardized a 34-pin interface for 5.25-inch floppy drives, which was for the most part a subset of the 50-pin interface, with the pins rearranged. Most 5.25-inch floppy drives provided spindle motor on/off control over the interface but had no head load solenoid, where previously most 8-inch floppy drives gave the interface control over the head load solenoid but had no spindle motor control. (Many of the later 8-inch half-height floppy drives followed this trend.) The Shugart Technology (a different company, later renamed Seagate) ST-506 drive standardized a 34-pin interface for 5.25-inch winchester hard drives, which was in most regards a subset of the SA-1000 interface, with a different pinout, and a different differential signalling standard (RS-422) on the radial data connector. When 3.5-inch floppy drives and hard drives were introduced, most used the same 34-pin interfaces as their 5.25-inch counterparts. All of the drives and interfaces previously described are bit serial, with discrete control lines for all drive functions. The interfaces have no parallel bus structures for either data or control. There were third-party hard disk systems for the IBM PC, but the first official IBM hard disks for PCs were for the PC/XT and PC/AT. The PC/AT controller in particular was based on a Western Digital design.The IDE hard disk interface was essentially the host interface of the Western Digital hard disk controller. As such, it uses a parallel data bus for both data and commands. There are no discrete drive control signals. > I was hoping to avoid some timings of the physical aspects of spinning the > disk and seeking. > Unfortunately not. A floppy drive doesn't have any way to know what sector the host wants, so a drive emulator has to simulate the rotation process. Most floppy interfaces, including those used on PCs, don't have buffered seek, so there's no easy way for the emulator to short-circuit the step process either, though you could possibly tell the computer to configure the floppy disk controller chip for a faster seek rate.
