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

From: Andreas Holz <asholz_at_topinform.com>
Date: Mon Dec 1 10:32:16 2003

Hello all,

I would like to see a substitution of the now rapidly dying
MFM/SMD-disks. I would appreciate if I could swap out a defective
Maxtor-XT/ drive, and an IDE-drive into my Symbolics or PDP simply by
connecting the "black-box" to the existing cables.

Andreas

Bob Shannon wrote:

>
>
> 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 - 10:32:16 GMT