* Posts by windsurfer

1 publicly visible post • joined 31 Oct 2013

Storage Memory

windsurfer

Re: Nothing new here. Move along

The first implementation of single level store was the Atlas computer in 1962, but the one I'm familiar with is Multics, the grandaddy of most operating systems. The project started in 1964 and was at its peak when I first learned to program on it in '73. We used PL/1 and when you opened a file, you got back an address (actually a segment) pointer which you mapped your structures to. I never had to use the traditional read/write operations. The *nix mmap() function does something similar (but not as cleanly, IMHO).

More relevant to storage memory is the idea of multi-level memory where the paging system would fetch pages from a progressively slower (and cheaper) hierarchy of devices. Multics implemented a paging hierarchy that was originally core memory, drum, and then disk. Later on, it was DRAM, core, then disk.

Here is the paper from '75 which describes the subsystem and concludes that the availability of cheaper memory outweighs the complexity of the page management:

http://bitsavers.trailing-edge.com/pdf/honeywell/multics/redell/mtb/MTB-170.pdf