Hi, On Wed, Jan 9, 2013 at 12:43 PM, dmccunney <dennis.mccun...@gmail.com> wrote: >>> >>> EMS used a 64KB page frame located in the block between 640K and 1MB, >>> and paged memory above 1MB into it for use. >> >> I vaguely thought EMS 4.0 didn't need a page frame? (Where's Eric to explain >> all this when you need him? Heh,) > > I don't recall. But the underlying issue is how you access stuff > above 1MB RAM on a CPU with a 1MB address space. For the CPU to see > it, it must be in the 0K - 1MB range, and that mandates copying it > from RAM above 1MB into that range. This means you need a defined > area in the 640-1MB range were it will be copied, and will mean you'll > have to page stuff into it in chunks that will fit in that area. > Sounds like a page frame to me.