Which calculators run RPL under the hood?

[rprosperi]

I believe ALL Pioneers are based on a SysRPL core, with varying maturity of the kernel as time progressed. It has been reported (I believe after an extensive disassembly) that the 42S used a larger amount of assembler code than other models, but this no doubt is due to being so early and requiring lower-level tweaks to accomplish the required 41 FOCAL compatibility. Creating all models on a common platform was one of the core goals when SysRPL was conceived. It is still cheaper/faster/safer to build a "low-end" model like the 20S on an existing platform than to create a new one, even if that model's demands are not high.

Also, the later derivatives of the 39g/40g series machines (39g+, 39gs, 40gs) were also RPL-based, but emulated on ARM, similar to the 48gii, 49g+ and 50g.

I believe the later derivatives of the Pioneers (10BII-Gold, 17BII-Silver, 33S, 17BII+, et. al.) were all re-implemented when outsourced to various firms in China. Later still, the 10bII-Silver and 10bII+ were then brought back in-house and done (in C?) by Tim I believe (the 10bII+ for sure).