The 80V max is not a problem for me. Since I was buying new motors, I simply bought 72V. I read that anything over 80V is lethal, so I'd just assume stay under that anyway.
My issues with the Gecko Servo drive are several. Prior to buying the Gecko and the 1,800 line encoder, Gecko tech support assured me that their 340 would not limit my speed with an 1800 line encoder, and that drive's 250khz pulse rate "can easily handle anything Mach3 can throw at it".
Well, it turns out that the 250khz limit is not only on the input side, but also on the encoder side, so even though you can multiply the inputs by an order of magnitude, you still hit a wall on the motor side. With the 1,800 line encoder, the Gecko limits my speed to about 2,080 RPM. The motor is capable of over 4,000RPM. The Viper can read encoder pulses at 625khz, which is over 5,000 RPM with an 1,800 line encoder.
The Gecko faults at a fixed rate of 147 steps. On a 300 line encoder, that's plenty, but on an 1,800 line encoder used on a spindle, the Gecko faults constantly on harmless tiny following errors. And the Gecko has no 'soft fault' It just shuts down the motor and does not recover which is a huge PIA, and the Gecko is not configurable in any way, so it is not possible to correct these issues. The Viper, by contrast, can have the fault steps programmed wherever you need them to be and it has a 'soft fault' where it will just issue a warning.
There are other annoying characteristics of the Gecko, but those are the two critical problems that make the Gecko unuseable in my application. The Viper has a lot of other very useful features, not the least of which is reporting back to a host via RS232 port. You can read the following erroe, and the mortor load in real time. With a VB macro or more likely a 'Brain' monitoring the servo, Mach3 could actually approach something like t a true closed loop system.
I've ordered the Viper, so we'll see how it goes. Incidentally, I have several of the Gecko 203V stepper drives and I am happy with those.