Disk hardware emulation, was Re: Grandfather system RTE6/VM?

On Fri, 28 Nov 2003, Bob Shannon wrote:

Another possibility is to emulate only the actual drive in hardware. That is a simple FPGA +ATA drive based device could emulate the magnetics and head positioning interface of the original drive. Then you could use the same disk controller and the system software would see no changes. Since there is so much excess storage available in current ATA drives, plus the original data rates are quite slow relative to a FPGA serial data recovery clock, an inefficient but simple to implement sector data record and playback data encoding scheme could be used, for example by storing ~5 bits per original data bit, the time between data transitions could recorded and replayed (with possible emulation of magnetic bit timing aberrations to undo the effects of write-precomp) (I think Eric Smith gave me this idea...) Peter Wallace