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It was not long until it became clear that DEC was once again entering the 36-bit business with what would become the PDP-10.

BBN started talks with DEC to get a paging subsystem in the new machine, then known by its CPU name, the KA-10.

DEC was not terribly interested.

However, one development of these talks was the inclusion of two dual memory areas, allowing all programs to be divided into a protected ( exec in DEC-speak ) portion and a user portion.

Additionally, DEC was firm on keeping the cost of the machine as low as possible, including only 16K words of core and placing registers in RAM, resulting in a considerable performance decrease.