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

From: Peter C. Wallace <pcw_at_mesanet.com>
Date: Sat Dec 6 10:48:34 2003

On Fri, 5 Dec 2003, Tom Jennings wrote:

> On Fri, 2003-12-05 at 14:28, Jules Richardson wrote:
>
> > > Construct an electrical interface of the simplest possible hardware to
> > > get the job done (electrical interface, buss termination as required,
> > > etc) and do the whole job in C or even Perl.
> >
> > I agree, with the only caveat being that the computer required doesn't
> > have to be something costing a large amount of money.
>
> As you point out, it can be a case-of-beer's-worth of computer, for many
> simulated devices.
>
> > The only coding effort is to talk to the custom homebrew interface that
> > handles ST506 or whatever flavour of drive you're needing to emulate.
>
> I take it ST506 has analog data for a controller-side separator; this
> makes it harder, but as others point out, it could be 'tricked' or
> probably simulated with an 8-bit flash converter, and/or use Duell's
> idea for an analog sector recorder!

The ST506 interface has _NO_ analog signals only digital... The only
interesting information is the time between transitions...


>
> Disk size being what it is today, you could probably record each
> "sector" as AtoD'd analog data in a userland program.

Much simpler, just record a bit atream...

>
> (My LGP-21's rotating memory probably contains interesting data, so I'm
> probably going to copy the tracks (32 physical) to disk with an opamp on
> the head windings driving a sound card, and post-process the NRZ data
> later. I'll likely take multiple copies of each track for safety.)
>
> > The hardware interface is the problem; in the case of ST506 it sounds
> > non-trivial and that's even assuming that once built the data stream
> > could be decoded and generated by the software (as I get the impression
> > that said data stream can change widely depending on what controller was
> > used to format the hard drive that you're emulating)
>


We dont need to decode that data stream, only record it and play it back...


>
> I'm guessing that for slow interfaces, SASI or maybe ST506, you could
> make a semi-generic hardware interface that had a dozen latched output
> bits, some input bits, an 8-bit DAC and ADC, and with only enough
> hardware drivers to talk to it, do the rest of the simulator in
> software.


No A-D needed...

>
> DMA-speed interfaces like SMD would require hardware buffering, and
> delays could generate timing issues in the controller. But I bet a lot
> of machines could use a slow interface.
>
>

Peter Wallace
Received on Sat Dec 06 2003 - 10:48:34 GMT

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