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

From: Bob Shannon <bshannon_at_tiac.net>
Date: Mon Dec 1 10:11:58 2003

Peter C. Wallace wrote:

>On Fri, 28 Nov 2003, Bob Shannon wrote:
>
<snip>

>
>>
>
>
>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
>

Given an ATA drive, its much simpler to emulate the controller to CPU
interface than it is
to emulate the controller to disk interface. This is especially true
for the MAC-series drives, but
totally untrue for the 7900 (which uses a pair of generic TTL-level I/O
boards).

If the controller is well emulated, the software again sees no
difference and runs normally
with a much smaller investement of design effort.

>
Received on Mon Dec 01 2003 - 10:11:58 GMT