[sebhc] 64K memory

[Patrick Rigney]

> Carroll Waddell wrote:
> > 
> > I hadn't thought about that. If we could find out the 
> commands for the 
> > H47, might be able to swing it. I've heard that the 47 
> interface was 
> > serial with all the smarts in the 47 drive.
> 
> No; it is an 8-bit parallel interface with handshaking -- 
> much like SCSI. In fact, I think the two are (nearly) interchangeable.

Guys, this is all really great, but I have a question/comment/perspective.
I'm looking at all this and wondering why Carroll wouldn't build some kind
of simple interface on his card, like bi-directional parallel, and simply
use a driver in HDOS and/or CP/M to control it and make it look like any
other drive?  It seems to me that, aside from the coolness factor of using
the vintage controller, you can get more performance and surpass any
architectural limitations inherent in the old hardware AND software.

I worked on a virtual disk subsystem some years ago for a pre-Palm
hand-held.  It used nibble-mode parallel I/O, and was very fast and
reliable, much moreso than serial (although it supported that as well).  The
control program on the PC was trivial, as was the driver in the hand-held.
That company ultimately didn't make it, but I used the same principles a
couple of years ago and started to build on them for a CP/M virtual
filesystem.  It became immediately clear to me that any number and size of
virtual disks could be created over this interface.  You can even create
them on the fly in any size and mount them.

I guess what I'm saying is, aside from the coolness factor of running the
old controller, writing and installing device drivers isn't that hard.  I'll
bet _most_ of the software is well-behaved and just uses the defined system
APIs for filesystem manipulation, so the particulars of the hardware are not
an issue--AutoScribe works the same on the H-47, Z-67, and H-37.  The driver
provides the abstraction, so my bias is to do what is cheapest, fastest, and
creates a lasting, stable solution with the hardware and let the driver do
its job.  One Z-80 PIO and a little glue on Carroll's board with a simple
driver would be all it takes and requires no additional hardware on the PC.
The '8/89 won't know if SY.DVD is a driving a 30-year old Siemens drive or a
3Ghz Dell. :-)

Just my 2p!
Patrick


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