Re: [gentoo-user] Advice for 64-bit n00b?

[Alan McKinnon <alan.mckinnon@gmail.com>]

On Wednesday 03 March 2010 17:29:06 Stroller wrote:
> Hi there,
> 
> A new (to me) server has 64-bit CPUs. By my standards this is a REALLY
> NICE high specification machine (I appears to be 2 x dual-core), but
> in fact it's about 3 years old & is one of the earliest Intel Xeons
> that supports 64-bits / AMD64 / EMT64. I think it is 64-bit Pentium 4,
> rather than Core 2 architecture.
> 
> # cat /proc/cpuinfo | head -n 25
> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 15
> model           : 4
> model name      : Intel(R) Xeon(TM) CPU 3.00GHz
> stepping        : 3
> cpu MHz         : 2992.346
> cache size      : 2048 KB
> physical id     : 0
> siblings        : 2
> core id         : 0
> cpu cores       : 1
> apicid          : 0
> initial apicid  : 0
> fpu             : yes
> fpu_exception   : yes
> cpuid level     : 5
> wp              : yes
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe
> syscall nx lm constant_tsc pebs bts pni dtes64 monitor ds_cpl cid cx16
> xtpr
> bogomips        : 5984.69
> clflush size    : 64
> cache_alignment : 128
> address sizes   : 36 bits physical, 48 bits virtual
> power management:
> 
> 
> I'm a bit confused by the 36-bit address size mentioned there, but I
> assume this is OK. The Gentoo wiki seems to confirm this CPU is 64-
> bit: http://tinyurl.com/klv7gc [1]

that is correct


> 
> Is there anything I need to know about working with 64-bits / AMD64 /
> EMT64, seeing as I've never done so before?

Nope, it's just another arch. The days of doing weird funky stuff to get amd64 
to work are long gone


> 
> I have started following the Gentoo Linux AMD64 Handbook, because the
> Quick Install Guide is described as "x86". Having untarred the stage I
> am surprised to find a lib32 directory. I thought compatibility with
> 32-bit binaries was optional. Or am I misunderstanding? This is going
> to be a headless server & I can't think that it'll need any binary
> packages - possibly the management utility for the RAID controller
> will be distributed as a binary, I'm not sure yet (the hardware RAID
> key was missing when I got this machine ☹)
> 
> I'm editing my make.conf and looked at the Gentoo wiki for "Safe
> Cflags" - it says 'CHOST="x86_64-pc-linux-gnu"'. But of course
> (according to make.conf.example) one shouldn't change CHOST on an
> installed system. Will the files in the stage 3 have been compiled
> using this CHOST?

Yes. If you used a recent amd64 stage, it will all be fine.
> 
> Any pointers would be gratefully appreciated - I'm wondering if
> there's anything you guys all take for granted that I could mess up if
> I don't allow for it early enough in the installation process.

In make,conf, as long s you are using a reasonably recent gcc:

CHOST="x86_64-pc-linux-gnu"
CFLAGS="-march=native -O2 -pipe"
CXXFLAGS="${CFLAGS}"


-march=native avoids all that tedious mucking about with trying to figure out 
what cpu type you should build for, and moves the heavy lifting off onto the 
compiler.



-- 
alan dot mckinnon at gmail dot com