Producing CPU upgrades for the RiscPC would be insane. Firstly, the non-CPU hardware is just too slow, and would rapidly become the bottleneck. (ie, a RiscPC couldn't keep one XScale stoked with data). Secondly, most people who keep RiscPCs do so to run ancient software that won't work on an A9 or an Iyonix; installing a bundle of XScales in it would be pointless.