I know there are many people out there that have problems getting Mach3 to talk to the Gecko G540. I know because I read a lot of threads trying to figure my problem out. I tried multiple parallel cards, etc.... Reconfigured BIOS, reinstalled software, etc, etc... Nothing ever worked.
The fix was pretty simple, and I came across it by accident. I was on eBay looking for another parallel card when I came across a motherboard from Intel that had a built-in DB25. I thought it might be an obsolete board despite the fact it said new in the ad so I went to the Intel website and sure enough they still make these motherboards with native DB-25 legacy devices.
Well after ordering and receiving an Intel DG41TX motherboard and a Celeron processor from Amazon my Taig mill is finally under computer control!
It is not an expensive motherboard and the processor didn't cost that much either. I wish I knew this from the get go.
I hope this helps someone out there.
(Newbie with Absolutely no Machining Experience)