Re: EMC compatible computers

[John Sheahan <jrsheahan-at-optushome.com.au>]

On Mon, Jan 13, 2003 at 06:41:02PM -0500, alex wrote:
> 
> There is a possibility of another hardware model without a  high cost.
> Consider a controller which consists of several low-speed mother boards
> connected together
> either through the parallel data link or the ethernet. 

remember the parallel port is dying. ethernet will be around longer.
the cost of interfacing to either is tiny compared to 
other related costs.

And the parallel port (electrical) performance sucks compared to any 
ethernet - particularly optical ones. 


> All the real time and
> close to the real
> time apps are handled by DOS (Free DOS). Front end is  handled by  Linux.
> DOS

DOS isn't real time.   perhaos using interrupts is - but then rtlinux
would work just as well.   And is more future-proof i think.

Still - it seems to me offloading the hard real time to an offboard
processor is noce. the interface to it is a lot less important. 



> can be serviced by a 386 single board PC. Linux - some kind of a Pentium.
> Software
> cost - 0. Hardware - not very high.

If I have learned anything - in small qty the sw cost is higher 
than the hw cost.  in large qty this reverses. 

> Alex