I/O for the future

A friend and I were talking about the demise of the ISA bus this
morning. (This is in my opinion really unfortunate, as the ISA bus is
a good one for simple hardware - about the only thing that could be
better would be seperate address and data lines). I pointed out to him
that by trying to do real time motion control on a desktop PC we put
ourselves in an interesting position:

We need the fast processors of newer machines to get high step rates,
but we need the I/O capabilities of the 1998 or so models which
typically have <200 mhz processors.

If we start to collectively get more into hardware step pulse
generators and the like, we may be able to go for a quite a while
buying up trailing edge machines with ISA. Lots of these are
available inexpensively, often in lots from companies that upgraded or
went belly up. I could see someone making a business of selling
machines (like the Dell Optiplex's a guy brought 20 of to my local
hamfest) with EMC already installed and configured for the hardware...
Even package them in pairs so people have a spare in case something
fails.

Another thing to look at would be the small industrial PC's - things
like PC/104. And cpu's on an ISA card. These are likely to retain
ISA (or functional similar busses in a different form factor) for
quite some time, but they are pricey if one wants the latest
generation processor.

My friend came up with an interesting idea: what about a USB-ISA
converter. This could take the form of an ISA expansion chasis (maybe
a board to drop into an old PC case) with a lot of slots, connected to
the PC via USB. It might also be available in a 'single slot'
version. For linux at least, all the I/O port access is done with
library functions, so it should be possible to trap access to
specified ports and tunnel it off through the USB to a microcontroller
on the other end that would convert it back to ISA. I suppose one
could also do something similar with PCI, or possibly even an enhanced
parallel port instead of USB. The advantage of course would be
continued ability to use current hardware designs, both the
specialized boards developed by our members, and older commercial ones
like the RT802 quad DAC I found in the trash at work...

Chris

PS - I wonder if one can optoisolate USB? Actually, running it over
TOSLINK fiber would be cool!

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT