x86 or amd64 arch

[NeddySeagoon]

Amity88,

It means that the mantissa is larger inside the FPU than that stored in memory.
I'm not sure what effect it has on Matlab and SPICE but we did have one interesting case here a few years ago when it made a big difference.
Unfortunately, google can't find the thread for me.

[V-Li]

I have a Dell laptop with following config
Intel Core 2 Duo T9600
2GB DDR2 800Mhz RAM
Intel GMA 4500

This is my company laptop and i've decided to move it to gentoo as well.
Now question is whether i should go for x86 or amd64.

I'll be using Sun Virtual Box quite a lot
There is no chance of any RAM upgrade.

I've used x86 in most of my machines till now
From what i've read there's little performance difference between two archs.

The impact is low, so the choice is completely up to yours. Sometimes (like Flash) 64bit is lacking some support.

I did notice that gnome went stable in amd64 weeks before same for x86.
Is this true in general? What would you guys advice

This depends. At the moment, x86 has 29 open requests, while amd64 has 57, so x86 is "better". This can change from time to time, but normally they are quite even. For comparison the last couple of Gnome stabilisations.

01 Aug 2010; Christian Faulhammer <fauli@gentoo.org> gnome-2.30.2.ebuild:
x86 stable, bug 324077

31 Jul 2010; Pacho Ramos <pacho@gentoo.org> gnome-2.30.2.ebuild:
amd64 stable, bug 324077
...
04 Jun 2010; Markus Meier <maekke@gentoo.org> gnome-2.28.2.ebuild:
x86 stable, bug #314899

...
03 May 2010; Olivier Crête <tester@gentoo.org> gnome-2.28.2.ebuild:
amd64 stable, bug #314899

...
17 Oct 2009; Markus Meier <maekke@gentoo.org> gnome-2.26.3.ebuild:
x86 stable, bug #281427

08 Oct 2009; Olivier Crête <tester@gentoo.org> gnome-2.26.3.ebuild:
Stable on amd64, bug #281427
...
15 Mar 2009; Markus Meier <maekke@gentoo.org> gnome-2.24.1.ebuild:
x86 stable, bug #260063

11 Mar 2009; Daniel Gryniewicz <dang@gentoo.org> gnome-2.24.1.ebuild:
Marked stable on amd64
...
08 Sep 2008; Markus Meier <maekke@gentoo.org> gnome-2.22.3.ebuild:
x86 stable, bug #236971

07 Sep 2008; Olivier Crête <tester@gentoo.org> gnome-2.22.3.ebuild:
amd64 stable, bug #236971
...
02 Feb 2008; Chris Gianelloni <wolf31o2@gentoo.org> gnome-2.20.3.ebuild:
Stable on amd64 wrt bug #208366.
...
01 Feb 2008; Christian Faulhammer <opfer@gentoo.org> gnome-2.20.3.ebuild:
stable x86, bug 208366

[Amity88]

@ NeddySeagoon,

Thanks for the info I have one last question, is the 64bit version of gcc any faster than the 32bit version?

[d2_racing]

GCC 64 bits will use 100% of the instructions available on a 64 bits processor and GCC 32 bits will leave all the 64 bits instructions stuff even if your processor is compatible.

Faster I don't know, but at least GCC will use all the power avaible on your processor if you own a 64 bits processor and you use GCC with a 64 bits installation.

[NeddySeagoon]

Amity88,

I suspect there is little difference but I have not tested.

[xibo]

the x86-64 has twice as many general purpose registers and twice as many sse registers as the x86 which should result in less cache/memory accesses.

it's 80 when using fpu, and 128 when using SSEx set.
So no, amd64 don't use 128 except when told to do so (mfpmath=sse will higher it as it will use SSE instead of FPU)

And it have nothing to do with amd64, x86 also use SSE@128bits

The Pentium 3 and Athlon XP have SSE, the Pentium 4 and Athlon-64 have SSE2. Also, all newer-to-those chips have SSE(2).
SSE uses 32 bit floating point numbers, or (SSE2) 64 bit double precision floating point numbers. The reason why the registers are 128 bit long is because SSE works with vectors of 4 floats / 2 doubles instead of individual values.