The design of the Pentium Pro bus was influenced by Futurebus, the Intel iAPX 432 bus, and elements of the Intel i960 bus. Futurebus has been intended as an advanced bus to replace VMEbus used with the Motorola 68000 from the late 1970s, but it stagnated in standardization committee for more than a decade if you count all the twists and turns. Intel's iAPX 432 initiative was also a commercial failure, but in the process they did learn how to build a split-transaction bus to support a cacheless multiprocessor system. The i960 had further developed the split-transaction iAPX 432 bus to include a cache coherency protocol, ending up with a feature set highly reminiscent of the original Futurebus ambitions.