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newbee guestion, confused about 32bit/64bit
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sammy2ooo
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Joined: 26 May 2004
Posts: 225

PostPosted: Wed Oct 20, 2004 9:38 am    Post subject: newbee guestion, confused about 32bit/64bit Reply with quote

hi folks

i just bought an old sparc station.

livecd root # cat /proc/cpuinfo
cpu : TI UltraSparc IIi (Sabre)
fpu : UltraSparc IIi integrated FPU
promlib : Version 3 Revision 10
prom : 3.10.4
type : sun4u
ncpus probed : 1
ncpus active : 1
Cpu0Bogo : 719.25
Cpu0ClkTck : 000000001575a9de
MMU Type : Spitfire

Now i am confused about how to use 64bit programs. Which import changes to the configs must be done, what must be done to ensure 32bit compatibility?

Any hints, links, suggestions appreciated.

Greets 8O
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GenTimJS
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Joined: 03 May 2003
Posts: 406
Location: NH, USA

PostPosted: Wed Oct 20, 2004 12:41 pm    Post subject: Reply with quote

In general, you are going to have a 64 bit kernel and a 32bit userland in linux

if you -need- a 64 bit userland, head over to www.sun.com/software/solaris
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krakadikt5k
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Joined: 26 Oct 2004
Posts: 18

PostPosted: Tue Oct 26, 2004 1:07 am    Post subject: amd64 = 64bit userland? Reply with quote

It seems that for some reason gentoo on a x86-64 64bit userland tools are avaliable.... not not on mips or sparc.... I was wondering if someone could maybe say why, and if we will get 64bit stuff on mips or sparc anytime soon. I've heard for mips its a compiler issue and will be fixed with gcc eventually.
-dan
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Kumba
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Joined: 16 Jul 2002
Posts: 373
Location: Sigma 957

PostPosted: Wed Oct 27, 2004 12:33 am    Post subject: Re: amd64 = 64bit userland? Reply with quote

krakadikt5k wrote:
It seems that for some reason gentoo on a x86-64 64bit userland tools are avaliable.... not not on mips or sparc.... I was wondering if someone could maybe say why, and if we will get 64bit stuff on mips or sparc anytime soon. I've heard for mips its a compiler issue and will be fixed with gcc eventually.
-dan


A full sparc64 userland is just uneccesary to be honest. The average application most commonly used by users would see no benefits from using 64bit stuff. Maybe large database apps and crypto/number crunchers would, but that's about it.

Mips is an entirely different story. Unlike sparc, which really only has 32bit and 64bit variants, mips has several (ABIs to be specific): o32, n32, o64, n64, eabi. o32 is basically "Old 32bit", or the binary format found in IRIX 5.x. n32 is basically "New 32bit", or the format found in IRIX 6.x. n32 is unique because it requires a 64bit kernel, and is really a 64bit format that runs with the same or slightly better speed of o32 (usually better). It's rather experimental in Gentoo/MIPS atm (I and a few others have poked at it, but it has many bugs and is not ready for consumption by the masses).

o64 is o32 "extended" to 64bit, and is generally regarded as a hack. It's only real use is to build mips64 kernels for SGI Indy and SGI O2 systems, and nothing more (an o64 binary is even regarded as 32bit by 'file'). n64 is the "true" or " new" 64bit format. A full n64 userland could be considered similar to a full sparc 64bit userland. Ideally, people using systems that benefit most from mips64 kernels (O2, Octane, Origin) would use an n32 userland, with a random app (like a big database) built for n64, but until that is stabilized, we're all stuck using an o32 userland.

The last one, eabi, I know little about. I believe this is a format geared more for embedded systems, but I'm not entirely sure. It's not one I've tinkered with really. Maybe in the future, we'll have some use for it.

As for amd64, I know little about that platform and cannot comment too much on it. Suffice to say, 64bit computing is not a new subject. Mips was one of the first processor architectures to produce a 64bit CPU back in 1990 with the introduction of the R4000. What amd64 is, is a 64bit computing platform available to the consumer masses. Before, it was primarily limited to Universities, Government, and Research fields.


--Kumba
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squash
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Joined: 22 Jun 2002
Posts: 79

PostPosted: Thu Oct 28, 2004 3:19 pm    Post subject: Reply with quote

Hi,

This has been covered elsewhere, so I'll be quick.

64 bitness on Sparc does little beyond doubling the sizes of registers. This means that when you run a 64 bit program, it takes the same execution path as a 32 bit one, but takes twice as much memory or many data types. In other words, you lose performance without any real upsides. Using proper CFLAGS to target v9 cpu will give you optimizations for your processor without moving everything to 64 bit.

x86_64 is a different beast. When you switch one of those into 64 bit mode, you not only get 64 bit registers, you get twice as many as in 32 bit mode. (16 vs 8, and they are all 64 bits wide). This goes a long way towards avoiding register starvation, having to use the stack, and so on. You also get a pile of 64bit specific operations. A program compiled in 64 bit vs 32 bit can be very different.

With that said, a few of us have some *really* unstable 64 bit userlands for sparc, which you can build if you have a lot of patience and a good knowledge of hacking software..

Josh
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