Slide 4 of 89
Cray worked at every level of integration from the packaging, circuitry, through the operating system, compiler and applications. Part of his success was his ability and willingness to work at all levels and understand every one of them deeply. He excelled at five P’s: packaging, plumbing, parallelism, programming and understanding the problems or apps.
By plumbing I include both the bits and heat flow. A lot of computing is a plumbing problem: deciding on bit pipes, reservoirs or memories, and interchanges (switches). Are there big enough pipes? And are the reservoirs big enough? After all what is a processor other than just a pump. Memory is a storage tank. Gene Amdahl’s rules state that for every instruction per second you need a byte of memory to hold it and one bit per second of I/O. That carries into Cray’s rule for every flops or floating-point operation per second you need a word of memory for holding the results and two memory accesses of bandwidth!