Operating Systems 2020W Lecture 23

Video

Video from the lecture given on April 3, 2020 is now available.

Notes

Lecture 23
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Last lecture (except for review!)

When you do PAE addressing on 32 bits, you're extending addresses to be
36 bits (to get 512G) or more.  Trouble is, standard pointers are 32 bits.

So normally on such systems individual processes would have 4G address spaces at most, and the kernel has to deal with pointers larger than 32 bits (really, page tables with more bits/levels).

Whenever your RAM gets bigger than your address space, you have pain.
(Apple //e's could have 128K or more RAM, but the 6502 had 16 bit addresses. So to get access to memory above 64K you'd swap it in in 16K chunks.  PAE does basically the same thing.)
  - you can't address all of memory with a single pointer