Certainly the published interface is constrained by what was "officially" released. Just pondering if there was an internal engineering roadmap from 16->18->22 bits around this time or did things evolve more discretely?
I think it evolved. Remember there was one type of core memory for the 11/03 that only worked in a 16 bit box as did the little 4k memory boards that required the 11/03 to do refresh cycles. Maybe the MSV11-CD memory board (had one of those) as well. I think it used "bits 16-17" for the +15,-5 or something like that and plugging an 18 bit card into a slot like that would cause the usual fireworks.
But back in the beginning your choice was RX01 floppies (interrupt so they didn't care), or the RKV11.
I've got the 1975 or so version of the 11/03 short book, I can take a look. But I remember very clearly the insanity of the RLV11 controller board with the whole BA11-S requirement for the CD bus (which was repurposed as the PMI on the 11/83). Always wondered if you could run an RLV11 in slots 2-3 on a BA23 box. Probably.
C
