Discontinued IC's: Fairchild (?) MB15604; FPGA?

PGA is a Pin Grid Array, which is a package type. No direct relation to the other terms. A PLA is a Programmable Logic Array. It has a programmable OR matrix followed by a programmable AND matrix. This is the most general combinatorial logic device, but has mostly been replaced by PAL, CPLDs, etc. An FPLA is a Field-Programmable Logic Array. There used to be mask-programmable logic arrays, but they're not really available as standalone parts any more, so the term FPLA has mostly fallen out of use. A PAL is like a PLA but with the AND matrix fixed. A PLD is a Programmable Logic Device, and can be almost anything. A CPLD is a Complex Programmable Logic Device, which just means one with lots of pins or terms. There's no well-defined threshold beyond which a PLD becomes a CPLD. An EPLD is an Erasable Programmable Logic Device. Since almost all current stuff is electrically erasable, this term has mostly fallen out of use. An FPGA is a Field-Programmable Gate Array. These typically are "finer-grained" than a CPLD; they have simpler logic elements, but more of them, and more routing resources. Maybe. But mostly I think it's more a matter of the lack of standardization, rather than attempted "control".