8" floppy project

On Tue, Jul 27, 2004 at 09:09:38PM -0700, Fred Cisin wrote: I don't recall either. For those that don't know, the Amiga doesn't have a traditional FDC chip - it uses a massive shift register in the sound chip to clock pre-encoded data on and off the disk, and uses logic functions of the graphics chip to convert entire tracks to and from MFM encoding. That's how they get 11 sectors/track - the intersector gaps are tiny compared to what a sector-oriented controller needs. One consequence of this scheme is that when they wanted to go to 2MB unformatted media (called "1.44MB" by PeeCee folks), they had two choices: create a new sound chip that could handle double the data rate, or halve the data rate of the floppy. They chose to monkey with the floppy. I have several of these - when the drive indicates 2MB media, the motor spins at half the rate so the sound chip can keep up. The upside of this is that you can put one of these floppies on an older Amiga and it will still work. The downside is that you can't steal a cheap/free drive from a PeeCee when your Amiga HD floppy drive dies. All of this aside, as flexible as the Amiga scheme is, there must be some inherent limitations or there would be no need to design a Catweasel. -ethan -- Ethan Dicks, A-130-S Current South Pole Weather at 28-Jul-2004 04:20 Z South Pole Station PSC 468 Box 400 Temp -100. F (-73.5 C) Windchill -131.8 F (-91 C) APO AP 96598 Wind 5.3 kts Grid 127 Barometer 673.6 mb (10868. ft) Ethan.Dicks(a)amanda.spole.gov http://penguincentral.com/penguincentral.html