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

From: Peter C. Wallace <pcw_at_mesanet.com>
Date: Sun Nov 30 11:12:25 2003

On Fri, 28 Nov 2003, Bob Shannon wrote:

>
>
> Mike Gemeny wrote:
>
> >>it's a museum!!! Emulate hardware for display?
> >>
> >
> >
> >
> >I agree, I’m running two 2883s on Access under simulation. I run a single
> >7900 on the TSB E version, and a single 2883 on the F version.
> >
> >
> >
> Ok, you can try to support 'classic' HP disk drives, and pay for
> filters, etc. Until your media
> wears out, or your heads need replacement. These are all life-limited
> components.
>
> But at some point the original disk hardware will no longer be practical
> to support. That time is
> fast approaching for all but CS/80 series disks, and they have a
> lifetime limit also.
>
> So at some point disk drive emulation will be the only option. Its
> important to develop these
> emulations NOW, while there are still some working 'real' disk drives to
> use as a reference for
> the development of the emulation.
>
> As for appearances, emulated drives can be built into the chassis of
> non-functional drives
> for a museum-quality appearance. But if you shun disk hardware
> emulation now it may not
> be as easy or practical to implement after the real hardware is gone.
>
> Personally, I've already bypassed emulating real HP disk drives and have
> developed my own
> disk controller for HP 1000's (not supported by RTE). RTE-IVB is such
> an ugly O/S I have
> no interest in running it, so compatibility with actual HP hardware was
> not as important as was
> making the device driver development and interface hardware as simple as
> possible.
>
> Now I run modern ATA (IDE) disk drives on my HP 1000's. This is just so
> much more
> practical than running real drives (including the real CS/80 disks I have).
>
> You might want to rethink your objections to disk hardware emulation.
> I'd be happy to help
> adapt my existing emulation scheme to include compatibility with 'real'
> HP disk drives.
>
> Another possibility would be to produce a kit-form of my existing ATA
> disk controller for
> HP collectors, but this would only be supported by HP-IL/OS, and not by
> RTE (unless
> someone wants to write an RTE driver for my controller!).
>


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
Received on Sun Nov 30 2003 - 11:12:25 GMT