The first model, Risc PC 600, was introduced in 1994 and up to 2003 being produced.
The Risc PC using the energysaving ARM RISC CPU, used nowadays in nearly all smart-devices like phones and tvs.
Expansions can be added by adding slices on top. There's also an option to expand/add a CPU.
Our machine has a StrongARM running at 233MHz and a 486DX4 running at 100MHz so this machine is capable of running Windows 95 inside the ROM- or disk-booted RiscOS 3.7.