I just wanted to compare the performance of the just arrived version of the HP12c with the latest one, running the 2015 firmware.
Both units are different from the original one (and around 150 times faster) but also different from the so-called HP12c+ that was produced around 2008. Both have an Atmel ARM-derived processor, but the newer model is far less energy consuming. Both can be reprogrammed (if you have the right firmware) and have the same connector, but the former used a different pin scheme, while the latter's protocol is USB (albeit with the same POGO-bsased connector).
I have run the simplest of programs for a minute:
02. GOTO 01
Both have exactly the same speed (within the accuracy of my finger starting and stopping the count). Notice the lack of "Hewlett Packard" in the lower part of the keyboard plate. We have just received a batch of the latest model, as well as units of the other current HP models.