Tony Duell asked about the difference between the two processors - here is what I found after a little google work; Steve The stuff below was brazenly copied from: http://www.everything2.com/index.pl?node=ARM2 "As soon as the ARM1 project was completed, work began on its successor, the ARM2, which later in 1985 became the first commercially available RISC processor. This processor was intended to correct some problems noted with the first design, and was aimed specifically for use in the Acorn Archimedes series of personal computers. While the ARM1 was a success as far as it went, there were some performance problems which needed to be fixed before it could be realistically used in the Archimedes. One of the key problems was a lack of hardware multiply support. This led to a software routine being used to do multiplication, using shifts and adds, which was "horribly slow", according to Steve Furber. This was fixed in the ARM2, by adding two instructions: MUL (multiply) and MLA (multiply with accumulate). These allowed the ARM2 to be realistically used for mathematical calculation, and very simple digital signal processing, in particular generating synthesised sound. Another issue which still affects most ARM processors even today is the lack of floating point hardware. Acorn decided to address this problem by adding hardware co-processor support to the ARM2, and at a later date intended to ship an optional floating point accelerator. Ultimately, the ARM2 FPA was never produced, despite demand from the Acorn user community: the first hardware FP came as an option with the ARM3 powered A5000, and around the same time a third party ARM3 and FPA upgrade was marketed by Simtec for all Archimedes computers. Finally, the design team noted that banking only registers R10 to R15 in fast interrupt mode was slightly over-frugal, and added R8 and R9 to that list. This increased performance of the very common FIQ by lowering memory accesses to stack registers. The ARM2 was manufactured at a slightly smaller fabrication size than the ARM1, 2.5?m as opposed to 3.5?m, had just over 25,000 transistors, and ran at 8MHz."