macmini's pata instead of parallel?

Initially I thought that 7i92 would be enough, but here's their website:
store.mesanet.com/index.php?route=produc...t_id=302&search=7i92
store.mesanet.com/index.php?route=produc...t_id=303&search=7i92
(are these the same boards, but the first one is just with two headers, while the second one has a proper lpt connector?)

anyway:

There are currently six 7I92M compatible breakout cards available from Mesa, the 7I74 through 7I78 and 7I85. The 7I76 is a step/dir oriented breakout with 5 axis of buffered step/dir outputs, one spindle encoder input, one isolated 0-10V analog spindle speed plus isolated direction and enable outputs, one RS-422 expansion port, 32 isolated 5-32V inputs and 16 isolated 5-32V 300 mA outputs. The 7I77 is a analog servo interface with 6 encoder inputs, 6 analog +-10V outputs, one RS-422 expansion port, 32 isolated 5-32V inputs, and 16 isolated 5-32V 300 mA outputs. The7I92 supports two breakout cards so for example a 10 Axis step/dir configuration or 12 axis analog servo configuration is possible with a single 7I92M and two Mesa breakout cards.

If 7i92 gives hardware step generation, why do they suggest using these Mesa breakout cards (yet another 200$), not a plain simple BOB?

Do you think having 7i92 + BOB + separate computer (macmini with linuxcnc) would be better than just a PC board + BOB? If so, I'll see what I can do to obtain 7i92.

A basic parallel port breakout board doesn't do much except maybe optoisolation and voltage buffering and you are limited to only 17 io points in the normal parallel port configurations, usually 5 inputs and 11 outs, and the optos are often rather slow junky ones.

A $200 7i77 does way more. It turns the ports 17 io pins from the FPGA card into 6 +/-10v DACs, 6 high speed differential (or single ended) encoder inputs (3 inputs each or 18 total), 6 enable outs (5 tied together 1 independent), plus 48 isolated digital I/O points (32 5-32v sinking inputs, and 16 5-28v sourcing outputs) and a RS422 Smart Serial port for further expansion. That is something like 75 separate IO points just on one card. (It would take 3 normal parallel port breakout boards just to equal the digital IO and they would probably not have the 24v tolerance. And you still would not be able to do the DAC.) There isn't a more cost effective way I know of to control an analog servo CNC machine.

If you only need a few IO points and just control some step dir drives there are much cheaper options than the 7i77 (the most expensive of Mesa's DB25 daughter cards.), but if your running servos it is one of the better choices.

If you are running steppers, one of the stepper oriented daughter cards can offer differential outputs for the step/dir connections to your drives. Plus all of the additional I/O options.
For a simple hobby machine a basic parallel port type breakout might be sufficient, but for a large industrial machine with lots of goodies and safety features, it probably isn't.