Modifying microcode

The microcode for the MicroVAX 2 (for which the MICRO2 assembler was used) and the CVAX (which is the CPU in your 3800) is implemented as a mask ROM on the CPU chip itself. No way to change it, and no way you can use MICRO2 to assemble the microcode for the CVAX. ?On 5/30/18, 3:19 PM, "cctalk on behalf of Kyle Owen via cctalk" <cctalk-bounces at classiccmp.org on behalf of cctalk at classiccmp.org> wrote: Has anyone attempted to reassemble and update the microcode on a MicroVAX? Seems like there's enough stuff here to possibly do it: http://simh.trailing-edge.com/semi/ucode/ I'm thinking about trying to find a microcoded architecture to play with before I design something around the Intel 3000 series. I've got a MicroVAX 3800, so I suppose I could run MICRO2 to assemble the aforementioned microcode. But then what? I assume PALs would have to be burned to implement the new microcode. Or is it more complicated than that? I don't have a PDP-11/60, unfortunately. I do have an 11/45, though...so with this modification, I suppose one could have some fun: http://repository.cmu.edu/cgi/viewcontent.cgi?article=3241&context=comp… Thanks, Kyle