Re: AMD64 impressions (Re: AMD64 box)

[David Rhodus <drhodus@xxxxxxxxx>]

On Nov 7, 2003, at 5:48 AM, Matthew Dillon wrote:
> 	The best comparison is the AMD box verse the P4 box.  Both are UP
> 	boxes.  The AMD box is 2.1x faster then the P4 box.  If clock speeds
> 	scaled, that would make the AMD box equivalent to 2.6GHz P4.  Since
> 	clock speeds don't scale, the AMD box is more like a 3.3GHz P4.
From most of my timing, the AMD 1.4ghz comes in around equivalent to my
P4 3.06ghz from buildworld timing. Also most of the numbers are a lot
lower on the AMD side as far as memory operations and context switches
which seems like a big benefit.
>     (2) The AMD's syscall overhead is very low compared to the P4.
> 	I ran the 'sc1' test in /usr/src/test/sysperf.  The AMD box
> 	comes back at 242nS/loop while the P4 takes 1300nS/loop and
> 	the DELL box (LEAF/SMP) takes 617nS/loop.

getuid() 0.916s 2402600 loops =  0.381uS/loop
on my AMD 1.4ghz.

I think big reason for the speed improvement here is because on every
syscall entry on a P4 you hit a branch misprediction and the AMD it 
cares
more about just blowing through the instructions which makes it a lot 
faster
at most things.

-DR