RE: Re[5]: emc on microway alpha pc?

["Eding, Bert" <b.eding-at-Nyquist.com>]

Just a remark on Your observations,
firewire is deterministic, fast and becomming cheap!
Our servoloop sample ticks go over firewire.
See www.nyquist.com

Bert

-----Original Message-----
From: Terry L. Ridder [terrylr-at-blauedonau.com]
Sent: vrijdag 13 oktober 2000 06:34
To: Multiple recipients of list
Subject: Re[5]: emc on microway alpha pc?



hello;

these are just some observations and my opinion
so take it for what it is worth.

opinion:
i personally would not risk damaging the motherboard
by using the motherboard's parallel port. call me
silly, but i personally will not do it.

observation:
usb and firewire are here and from looking at computer
motherboard offerings the onboard parallel port's days
are numbered. matt shaver and i discussed the disadvantage
of both usb and firewire being non-deterministic.
that leaves few options. once usb and firewire become
mainstream the only option is going to be parallel
port cards (either pci or isa, maybe pcmcia cards).

suggestion:
figure out how to make emc and perhaps your
external controller work just as good as they do now
with usb and firewire. 

jon> On Thu, 12 Oct 2000, Jon Elson wrote:

stratton> stratton-at-mdc.net wrote:
stratton> 
stratton> The ISA bus may well be a bottleneck for many things in today's
stratton> computers, but motion control I/O is not one of them.  No one runs
a
stratton> parallel port anywhere close the 8mhz or so limit of the 8bit ISA
bus.

jon> 
jon> Perhaps not for running step & direction stepper drivers, but for
running
jon> the motion control boards I'm designing for the parallel port, it IS a
jon> bottleneck.  Using an on-the-motherboard ECP port, I get about 600 K
jon> bytes / second (1.6 uS per transfer), without using the special burst
I/O
jon> instructions on the x86 architecture.  This is on a 100 MHz Pentium.
jon> I get about 20 uS per byte with an ISA SPP card, although this
jon> requires the software to do the EPP handshaking, so it is not a
jon> fair comparison.  Since I have to read, and write, more than a dozen
jon> bytes each, every servo cycle, the overhead becomes a concern,
jon> at least.
jon> 
jon> Jon
jon> 

-- 
Terry L. Ridder
Blue Danube Software (Blaue Donau Software)
"We do not write software, we compose it."

digging deep, i feel my conscience burn
i need to know who and what i am
this hunger jolts me from complacency
rocks me, makes me meet myself
----kendall payne---closer to myself---