[Info-vax] Comparison between Nehalem-EX and Power7

[glen herrmannsfeldt]

Michael S <already5chosen at yahoo.com> wrote:
(snip)
 
< In general, current incarnation of x86-64 instruction set architecture
< (a.k.a. AMD64,  a.k.a. Intel 64) is limited to 48-bit _virtual_
< address space. That's probably would suffice for a couple of
< decades.Going beyond that would require some, hopefully relatively
< small, changes to system-layer architecture - may be a new page table
< format. User-layer stuff shouldn't be affected.

I haven't looked at x86-64 so closely yet.

It is usual to have multiple levels of tables to avoid large
tables with many entries, and to allow for paging of the tables.

S/370 and VAX use two levels of tables, segment/page for S/370,
and two levels of page tables for VAX.

The 64 bit extension to S/370, z/Architecture, uses five levels,
with some tricks to avoid the need for all five until addresses
get that big.

-- glen