[tmead]

We're running Mach3 on a Compaq evo P4. After some poor initial performace running steppers I looked at the signals at the parallel port. The pulses are not regular when viewed on a scope. Seems that every third/fourth pulse is reasonably OK, but in between they wander or are not present.
Changing from ACPI to Standard PC made no difference.
The Compaq is running a fresh install of XP, with the network adaptor disabled and no other software installed.
Oddly the issue is almost identical on a Dell 620 laptop with a docking station parallel port.

I'm hoping to try a PCI video card tomorrow and disable the onboard video. The other thing that I've heard may be an issue is the USB keyboard ? We also have a logitech wireless mouse, but it does plug into the standard mouse port.

Any more suggestions ? Maybe i need to find some older hardware ?

Tim

[neilw20]

I use a USB to PS2 adapter for keyboard, and plug into the PS2 socket.
USB port can have time latency problems, which makes the keyboard scan timing erratic.
This was noticeable as clunking (erratic drive but never used a CRO on it) when holding down a jog key for continuous movement.
Also using the space bar to pause was unreliable and it is not good for the ESCAPE key to be delayed.

[tmead]

Just to let you folks know - Its working now !

I tried pretty much every adjustment I could find reference to for the compaq evo that I was using. By this point I had a clean XP pro install with no other software, no internet connection, moved to a standard PC setup, disabled everything that was non-essential (USB, network) and moved to a PS2 keyboard and mouse. Still irregular pulses and crap motion.

Swapping to an Athlon 2200 based PC gave some interesting results, with motion that speeded up with movements of the mouse, but at least it was smoother ! Swapping to a PS2 mouse/keyboard made no difference. Changing to standard PC setting fixed that and it ran sweetly.

I need to give the Athlon PC back (it's from home and my kids are getting irritated about the lack of internet etc !), so I bought a parallel card for the Evo. It's a startech PCI1PECP. That's the answer ! Even on the plain vanilla XP setup without any mods it is working really well. The change is definitely in the parallel port. There are loads of Compaq Evos around out there, and the onboard parallel doesn't work for cnc !

Sadly the original evo that had all the mods is now pretty dead. It had a partition reshuffle to allow a dos partition to run turbocnc (same juddering progress form the onboard parallel) and all the windows tweaks suggested on forums and artsoft. It's now firmly dead, as XP wont even start in safe mode after I tried to set it back to the normal configuration - oh well, back to a re-install I suppose !

Tim

[neilw20]

There is an example of an on-board parallel port that won't respond in a timely manner to Mach3.

Looks like trying a separate parallel card is the cheapest and easiest first diagnostic after the driver test.

Considering how cheap you can get cards, easier then OS re-install unless your time has no value at all.

[tmead]

Certainly it's the first thing I'd try. The new card was less than 20GBP, and I'm sure if I'd tried I could have found a cheaper one.
Having now tried two Compaq Evos (company has a stock of them !) that both show the same issue with the onboard port this is a likely candidate.

Tim