29 Oct
2010
29 Oct
'10
12:03 p.m.
Johnny Billquist [bqt at softjar.se] wrote:
Now, I direct you all to page 4-7 of that document,
which talks about
physical addresses on a VAX.
Notice how a physical address on a VAX can be 34 bits, while the
virtual
address is only 32 bits.
VAX virtual addresses have always been 32-bits although system space S1
(the top 1GiB) was never defined. The XVA project allowed it to be used
(on some hardware platforms).
The (related) XPA project allowed the physical address space to grow
beyond
1GiB but only to 4GiB (32-bits).
DEC STD-032 does allow for a 34-bit PA implementation but I don't know
of
one. The VAX 6000/7000/10000 all only implemented 32-bit PA mode
(afaik).
I don't know (off hand) whether the chipset could do more.
So (barring any inormation to the contrary) I think it's only a
theoretical
possibility :-)
Antonio