A little history, if it helps...
The EXOS2 PMC8 is basically an LXD75 with decent bearings on all axes and a belt drive (yes, I know that yours had problems with your beaings, but I really can't recall hearing of another that was similarly afflicted). The mount's design is therefore old, but like others of similar vintage, it still works. Basically, ES added the PMC8 to two pre-existing mounts (EXOS2 and the G11), thus putting most of the development investment in the controller and associated software and not as much the hardware.
The little iExos-100 is a new mount design that came later, appearing to take cues from the Losmandys. The RA, at least (not sure about the DEC) has a wheel gear, not a ring gear. Much better. Lots of folks doing well with the little guy, though some who are swinging bigger glass have benefitted from a tripod/pier upgrade.
The heavy silver-box PMC8 controller is intended for use in harsher conditions. The box is a big heat sink, with what's said to be a conformal coated board, etc. inside. Designed for the mount-that-lives-in-your-observatory sort of situation, whether you need that or not. Overkill, at the price point, but I can live with that... I've seen vids of EXOS2's used that way, but I expect the G11's would be more common. Wes and Jerry did a custom upgrade for a fer-really observatory in the southwest US, that I believe used the silver box.
The iExos-100 doesn't use the same physical board. It's smaller and less expensive, with better connectivity features but otherwise functionally equivalent, AFAIK.
The PMC8 controller itself is an interesting design. It's based on the Parallax Propeller chip. It's quite unique as a real-time processor. No interupts, etc. Instead, you have eight small CPUs, clocked in round-robin fashion, with shared memory in the middle. Each CPU gets its time slice. No funky debugging of transient real-time events, as each CPU has its own role. Firmware's on board, and appears to be straightforward to debug and upgrade. More details are in the Programmers reference, which should install, along with the ASCOM driver sources.
Hope this helps...
Edited by Devonshire, 03 April 2023 - 05:38 PM.