Microcode, which is a no-go for modern designs

On 01/02/2019 02:31 AM, Paul Birkel via cctalk wrote: Random logic instruction decode was a REAL issue in about 1960 - 1965, when computers were built with discrete transistors. The IBM 7092, for instance, had 55,000 transistors on 11,000 circuit boards. I don't know how much of that was instruction decode, but I'll guess that a fair bit was. The IBM 360's benefited from microcode, allowing them to have a much more complex and orthogonal instruction set with less logic. But, once ICs were available, the control logic was less of a problem. But, microcode still made sense, as memory was so slow that performance was dictated by memory cycle time, and the microced did not slow the system down. Once fast cache became standard, then eliminating performance bottlenecks became important. And, once we went from lots of SSI chips to implement a CPU to one big chip, then it was possible to implement the control logic within the CPU chip efficiently. Jon