I'm curious as to exactly what is meant by "external memory"? They must mean memory on the Synchronous Backplane Interconnect: http://gunkies.org/wiki/Synchronous_Backplane_Interconnect I.e. what most of us would call 'main memory'. If this code didn't even allocate main memory by pages, instead of in process-size blocks, it sounds like it's much like 32V (or is it 32V that's being discussed; I thought this thread had moved on to the Reiser demand paging version - my apologies it I've gotten lost). Also, this note: http://gunkies.org/wiki/Talk:CB-UNIX from Dale DeJager (which he kindly gave me permission to post) gives a fair amount of detail on the relationship between the Research and CB/UNIX versions, with a brief mention of USG - precisely the era, and relationships, that are so poorly documented. Interestingly, he indicates that the early versions of what later became CB/UNIX used something in the V1/V3 range (V4 was the first one in C), so it dates back earlier than most people apparently assume. If anyone else has any first-hand notes (i.e.from people who were there at the time), about the relationship between all the early systems, for which the author has given permiosssion to post it, please send it to me and I will add it to the appropriate article on the CHWiki. Probably the most needed is more about the roots of USG; Dale has filled in CB/UNIX, and the roots of PWB are covered fairly well in the BSTJ article on it: https://archive.org/details/bstj57-6-2177 at least, for PWB1. Anything that covers the later PWBs would likewise be gratefully receied. I suppose I should also write up the relationships of the later UNIXen - 32V and its descendants too - any material sent to me about them will be most gratefully received. (If anyone want a CHWiki account, to write it up themselves, please let me know). Noel