Ubuntu 14.04 LTS 32-bit vs. 64-bit Performance

[whitecat]

PAE really really sucks.

For me it's morre interesting to see comparison of 8-16GB RAM system with PAE on 32bit vs 64 bit.

But PAE testing is good idea

PAE really really sucks.

The biggest single reason to go 64-bit is exactly
because of physical address space. Your virtual address
space needs to bea multiple of the physical one:
when you hit 1GB of RAM, 32-bit virtual memory is no longer
acceptable. You literally do need more virtual memory than
physical.

PAE turned that very simple fact on its head, and screwed
things up royally. Whoever came up with the idea was
totally incompetent, and had forgotten all the DOS HIGHMEM
pains. There's a damn good reason why we left the 286
behind, and started using 386's, instead of having HIGHMEM
crap with windows into a bigger physical space.

Repeat after me: virtual space needs to be bigger than
physical space. Not "as big". Not "smaller". It needs to
be bigger, by a factor of at least two, and that's
quite frankly pushing it, and you're much better off
having a factor of ten or more.

Anybody who doesn't get that is a moron. End of discussion.

[...]

So repeat after me: PAE didn't ever really fix anything.
It was a mistake. It was just a total failure, and the
result of hw engineers not understanding software.

So no, PAE does not mean that you can use more than
4GB of RAM. Even before PAE, the practical limit was around
1GB, and PAE didn't move that post a fraction of an inch!

http://www.realworldtech.com/forum/?threadid=76912&curpostid=76973