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

From: Peter C. Wallace <pcw_at_mesanet.com>
Date: Tue Dec 9 22:45:45 2003

On Tue, 9 Dec 2003, Eric Smith wrote:

> The part of the ST-506 disk emulation that's of most concern to me is
> whether anything needs to be done about write precompensation. The
> controller shifts the pulses on write to compensate for the peak
> shifts that happen on magnetic media when flux changes are recorded
> close together. If the emulated drive does not emulate the peak shift,
> the read data timing will be further from the nominal timings that that
> the controller expects. This will affect the controller's data
> separator PLL. I'm guessing that it won't be enough to cause
> reads to fail MOST of the time, but it will reduce the timing margins
> enough to that it could potentially cause occasional soft errors.
>

Right, one option would be for the emulator to have a FM, MFM or RLL front end
and actually decode the bitstream. Then the write-precomp could be undone...


Peter Wallace
Received on Tue Dec 09 2003 - 22:45:45 GMT