Introduced in March 1975, the /70 is the bigest of the -11s. The KB11B  is a re-enginered version of the /45's CPU, with some new features. Two of the most important changes was the addition of cache (2 KByte of bipolar memory) and the 22-bit memory management. The latter enables the usage of memory up to 2 Mwords, using the UNIBUS map, which translates 18-bit UNIBUS addresses to 22-bit physical addresses. The kernel/supervisor/user operating modes and the MMU was standard. Important options: FPP, MASSBUS adapters (RH70's, up to four) with direct memory access.

The original processor had the floating point unit of the /45, which turned out to be ineffective, so it was resdesigned (KB11C). Overall performance is 0.6th of the VAX-11/780.

A normal system occupied at least two H960 cabinets (memory and CPU), the UNIBUS expansion needed another. There were also later revisions sold in another cabinet, without the front panel (Datasystem 570?).