3 ms·
I'm a big pdp-11 fan but this wouldn't have worked because 128K address space isn't enough even in 1975. Listen to Dave Cutler talk about this in the 3h long in
by dboreham 3y ago
I'm a big pdp-11 fan but this wouldn't have worked because 128K address space isn't enough even in 1975. Listen to Dave Cutler talk about this in the 3h long interview.
- clausecker 3y agoThe 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