Quentin Garnier wrote:
> On Mon, Dec 11, 2006 at 11:22:13AM +0100, Gilles Gravier wrote:

> > Your system will be shuffling double quantities of information from 
> > memory to CPU and back... and CPU will be doing computation on double 
> > the size of objects. Very often (except in some specific cases) this 
> > results in slowing down your machine compared to 32bits.
 
> That's not entirely true either;  the processor has many more registers,
> so the stack is less used, and functions parameters are not passed on
> it, so depending on the code, there might be less memory activity.  I'd
> be interested in seeing numbers for the syscall latency, too.

Consider the usual suspects like lists, hashtables and such. Since in C
these are typically pointer- not index-based they'll be twice as large
on a 64-bit architecture. Also many software historically makes use of
"long" when you need at least 32 bits. Software which makes heavy use of
any of these definitely needs more memory to accomplish the same tasks.
It's certainly not as bad as twice the amount on average. Albeit I suspect
there are optimizations (more registers) available in 64-bit mode which
outweigh this penalty in part and won't be accessible in 32-bit mode.

Also what about the NX-bit? Is that available or used by NetBSD in 32-bit
mode?

-- 
Christian