Extremely CISC instructions

On Wed, Aug 25, 2021 at 7:07 PM ben via cctalk <cctalk at classiccmp.org> wrote: Well, it might do.There is no requirement for the PERQ machine code instruction set to include that, or any other particular instruction. The PERQ loads its microcode from disk when it boots. The hardware that the microcode runs on is pretty much RISC, for example all but one class of instruction [1] execute in one microcycle. You can have just about any machine code instruction defined in the microcode, yuu could have the CRC or POLY instructions if you wanted them. I remember a 'competiton' some years back for the shortest machine code ROT13 encoder/decoder, somebody submitted a 1-instruction solution for the ERQ, the catch being tht of course it needed an extra bit of mcrocode to implement that instruction. [1] Those being the instructions that load the microcode control store. These take 2 microcycles. That was pretty much done in the hardware (the 'combiner PROMs'). The microcode handled generating the memory addresses and starting the appropriate overlapped memory cycles, the hardware aligned the words (barrel shifter) and combined them with the appropriate logical operation. Most PERQ2T2s were actually landscape (1280*1024 pixels) But I'l skip the emulation. After all there are 3 classic PERQs and an AGW3300 rather close to me here... -tony