Editing Memory management unit (section)

=== Segmentation plus paging ===
Some systems, such as the [[GE 645]] and its successors, used both segmentation and paging.  The table of segments, instead of containing per-segment entries giving the physical base address and length of the segment, contains entries giving the physical base address of a page table for the segment, in addition to the length of the segment.  Physical memory is divided into fixed-size pages, and the same techniques used for purely page-based demand paging are used for segment-and-page-based demand paging.

The [[Signetics]] 68905 MMU, designed for the [[Motorola]] [[Motorola 68000|68000]], [[Motorola 68010|68010]], and [[Motorola 68012|68012]] microprocessors, supported segmentation and paging.<ref name="signetics 68905">{{cite book |url=http://www.bitsavers.org/components/signetics/_dataBooks/1986_Signetics_Microprocessor.pdf#page=579 |title=Microprocessor Data Manual 1986 |pages=2{{hyp}}568-2{{hyp}}598 |publisher=[[Signetics]]}}</ref> Both Signetics and [[Philips]] produced a version of the 68000 that combined the 68905 on the same physical chip as the processor, the [[Philips 68070|68070]].<ref name=Zehr/>