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The PDP-11 had virtual memory in later models and could address more real memory than the 8086 afaik.
by clausecker 3y ago
The PDP-11 had virtual memory in later models and could address more real memory than the 8086 afaik.
- JPLeRouzic 3y agoAre you sure the PDP-11 has virtual memory in later model? They improved memory space because QBUS went from 64K (16 bits) to 256K (18 bits) to 4M (22 bits) but always usable only within a 64K window. But I don't think it has way to resume instruction execution when encountering a memory trap. You must be thinking of the VAX-11 where virtual memory was an explicit goal in its architecture (hence its name). https://en.wikipedia.org/wiki/VAX https://en.wikipedia.org/wiki/VAX
- clausecker 3y agoThe PDP-11 has virtual memory with 8k pages. There are four address spaces of 64k each, one each for supervisor/kernel/user and for each of these text/data. This was extensively used with e.g. 2.11BSD to cram programs into the address space that are way too large for what the PDP-11 can do. And yes, that includes the ability to resume on memory trap. You can read more on the Gunkies site: http://gunkies.org/wiki/PDP-11_Memory_Management http://gunkies.org/wiki/PDP-11_Memory_Management