[nzlug] 32bit vs 64bit speed/performance

[Robin Sheat]

On Tuesday 16 October 2007 23:00:53 Daniel Pittman wrote:
> No, and generally no one will.  The performance gain from all those
> extra registers is generally eaten up by the fact that your CPU cache
> just got cut in half and your programs spread out over all those extra
> cache lines to accommodate those larger pointers.
Cut in half? Pointers are larger, that's really about it. I don't think 
(haven't looked) that the instruction set size is much different, and most 
data other than pointers won't be larger either, so the amount of 
cache 'lost' will be very application specific, and half in the worst case.

> All that said I will be using 64-bit on my new desktop around the time
> Gutsy is released and living with the pain.
I've been using 64-bit Linux since about this time last year, and the only 
issues I have is that flash is a bit flakier using nspluginwrapper, and that 
the GWT browser doesn't work, as it uses Java ints (32-bit) to store pointers 
to talk to native code. Much 32-bit binary code will work, although it's not 
uncommon to not have the 32-bit libraries installed. In some cases there is a 
32-bit version in the repository, and they can happily co-exist. In both 
these cases, the work arounds are to install 32-bit java and 32-bit firefox, 
but I haven't found the need to do either.

I can't do speed comparisons, because I've only ever used 64-bits on this 
machine (Athlon X2 4600+ or something), the number crunching I do do on it is 
quite quick, and DVD ripping can do about 66FPS on one core (leaving the 
other one free to play 3D shooters at max res and detail :) Although, in both 
those situations there will be a lot more in play than just word size.

I'd recommend it if you don't mind a small extra bit of hassle, if only 
because it gives you the feeling that you're using all of your machine :)

-- 
Robin <robin at kallisti.net.nz> JabberID: <eythian at jabber.kallisti.net.nz>

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