Machines with >= 4GB of RAM

[Julian Elischer]

Obviously for >4GB you need PAE
but at one stage it was required that to run with 54GB of ram the kernel
base was moved down from the 3GB point (0xc0000000) to the 2GB point 
(0x80000000)

Is this still required?
And what is the configuration value to achieve this?
I've been trying to thing os search criterea that would
retrieve mails that spell this out and searched the
handbook, but without too much success.

I'm guessing that

options  KVA_PAGES=512

may be a start, but is it still required, and do I have to change anything 
else to match it?
(where does the Makefile work out where to link the kernel for?)
  Is a value of 512 enough for a machine with 16GB of RAM?

Any hints, (even a better google search string) appreciated.

Julian