A few more tantalizing crumbs of info about Voyager's CCS ISA: it has just 64 opcodes, per the instruction layout I posted previously. One of the people who worked on Voyager has said it's a relatively normal set of operations for the vintage and architecture. Arithmetic, I/O, tests, branching etc.
But one unusual aspect that's alluded to is that some commands (I/O specifically?) have "individual" and "tandem" variants.
