The 1800 used the 1130's instruction set but from what I heard the CPU was faster. (Integer multiply and divide in particular). And it had some other differences, e.g. index registers were real registers, not the first three locations of core. Also it had a couple more instructions, and the ability to make sections of core readonly once initialized -- I believe this was done with toggle switches rather than under software control. It's been a while. From what I wrote on ibm1130.org/today, apparently at one time I believed Mike Ross and Bob Rosenbloom have 1800's
I have never found a copy of MPX either as a distribution card set or disk image. Would LOVE to have it so we can try it out on the ibm1130 simulator in simh Brian
