That AT&T RISC CPU: the Hobbit.
According to Jimbo's bag of unbelievable tidbits:
However, the Hobbit-based Newton was never produced. According to Larry Tesler, "The Hobbit was rife with bugs, ill-suited for our purposes, and overpriced. We balked after AT&T demanded not one but several million more dollars in development fees." Apple dropped their interest in the Hobbit and moved on to help form Advanced RISC Machines, ARM, with a $2.5 million investment. When the company sold their stake in ARM years later, they netted $800 million.
And a very interesting note:
One interesting side effect of the Hobbit design was that it inspired designers of the Dis virtual machine (an offshoot of Plan 9) to use a memory-to-memory-based system that more closely matched the internal register-based workings of real-world processors. They found, as RISC designers would have expected, that without a load-store design it was difficult to improve the instruction pipeline and thereby operate at higher speeds. They felt that all future processors would thus move to a load-store design, and built Inferno to reflect this. In contrast, Java and .NET virtual machines are stack based, a side effect of being designed by language programmers as opposed to chip designers. Translating from a stack-based language to a register-based assembly language is a "heavyweight" operation; Java's virtual machine and compiler are many times larger and slower than the Dis virtual machine and the Limbo (the most common language compiled for Dis) compiler. Android's Dalvik virtual machine, the Parrot virtual machine and Lua virtual machine are also register-based.