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On 9/4/07, Roy J. Tellason <rtellason at verizon.net> wrote: GALs and PALs are similar devices, with a few key differences... PALs are bipolar devices, and are programmable once. GALs are made of newer technologies, like FLASH or EAROMs, thus can be erased and reprogrammed a number of times. PALs come in pre-coded flavors like 10L6 or 16H2, meaning 10 inputs with 6 low-true outputs or 16 inputs and 2 high-true outputs. With PALs, you took a fistful of your equations, then you, yourself, picked a part in which the equations would fit. To make a complex product, you might have 6 or 8 or 10 flavors of PALs in the same design. GALs are "Generic Arrayed Logic", thus are not pre-configured for certain geometries. A small part would routinely be described as a 16V8, meaning _up to_ 16 inputs and _up to_ 8 outputs, with Versatile choice of high true or low true for the outputs (also there were "registered" PALs like the 16R4 with flip-flops on the outputs for clocking or latching - GAL outputs are also optionally "registered"). In the early 1980s, PALs were popular because one PAL could replace a dozen TTL parts. GALs became popular because you only had to stock one type of 18-pin part, one type of 20-pin part, one type of 24-pin part, etc., rather than well over a dozen non-interchangable, non-reprogrammable parts. Eventually, even GALs were too simplistic for most professional product designs, but they are still popular with hobby projects - look at the Spare Time Gizmos line to see how easy it is to make GAL-based projects. GALs are still readily available for $1 or less. I don't think they've made PALs in a large number of years (not that there aren't still millions of loose parts on the resale market). Hope that illuminates more than obscures, -ethan