[mdlug] opensuse 64 bit vrs 32 bit advantages speed etc.

[Aaron Kulkis]

Dan Pritts wrote:
> On Fri, Nov 02, 2007 at 11:01:31AM -0400, Raymond McLaughlin wrote:
> [aaron kulkis quoted too]
> 
>>> 4) buy 64-bit hardware, install 64-bit OS and run
>>>     both 32-bit and 64-bit code.
> 
>> Option 4 is a available on *some* Intel 64 bit processors.
> 
> Any 64-bit intel CPU you'd buy in a "PC" would qualify.  You'd have
> to go way out of your way and pay a lot more money to buy an Itanium.
> 
> Core 2 Duos are 64-bit; "Core" (what you might think of as "core 1")
> CPUs are not.
> 
> There are 64-bit versions of the pentium 4 & celeron, as well as
> Current xeons are, I think, core2-based.  some of the older p4-based
> Xeons.  Current xeons are, I think, core2-based.
> 
> The relevant intel marketing word is "EM64T".

But which of those are capable of booting up to a
64-bit operating system and then running 32-bit
code? -- it's NOT a trivial thing -- we had 64-bit
CPUs for over a decade before AMD developed one
that could accomplish this feat.


> 
>> My off the cuff recollection is that when Intel first entered the 64 bit
>> market their product, codenamed Itanic^h_um was a fresh new architecture
>> with no backwards compatibility, and thus unencumbered with concerns
>> about supporting legacy code.
> 
> It is not compatible with x86 but it might be with HP PA-RISC.  Not sure;
> but the architecture comes out of work done originally at HP and it was
> certainly the market successor to PA-RISC.

I believe Itanium was a joint HP/Intel project for HP's
next generation of HP-UX workstations.

And then Intel got miffed when HP switched from
PA-RISK CPUs to x86 architecture instead of Itanium.

> 
> A relevant intel marketing word for Itanium is "IA64".
>
>>> Basically, the 64-bit platform is not yet ready for
>>> general purpose computing -- it fulfills certain
>>> niche areas (massive finite element analysis,
>>> extremely large database operations, etc) but has
>>> not yet been completed in many areas.
>>>
>>> Even on AMD-64 chips, which can run 32-bit code
>>> in a 64-bit platform (the only CPUs I know of which
>>> are capable of doing this), there are currently
>>> a lot of problems still.
>>>
>>> Unless you have some bleeding-edge NEED for
>>> 64-bit code, my advise is to wait until this
>>> mess is all sorted out -- it's probably going
>>> to take another 12 - 24 months.  Personally, I
>>> don't need the frustration, and NOTHING that I
>>> do would benefit significantly from 64-bit install,
>>> but a lot would be degraded significantly if I
>>> were to go that route at this time.
>> I disagree with this assessment. I would have had more validity 18
>> months ago but the software has matured in that time, and of late you
>> would really need to go out of your way to buy a 32 bit machine, eg
>> closeouts and refurbs. Aguablu good enough for now, but also closer to
>> the end of its life cycle and support cycle.
>>
>> And on a x86_64 machine you could install 32 bit everything and be
>> happy, or provided your distro carefully (I can vouch for openSuSE) you
>> can install 64 bit and be just as happy and arguably better off for
>> having made the transition.
> 
> Red Hat supposedly does a good job of including 32-bit compatibility
> libraries too (I know I install lots of compatibility libs on my
> servers but i generally run native 64-bit code).  I think windows
> does OK too but I'm sure there are exceptions.
> 
> There are a few other enhancements that were made in the AMD64
> architecture that can help beyond the extra address space.  The one
> that comes to mind is that they doubled the number of CPU registers;
> i've read that x86 is "generally felt to be a register-starved
> architecture" so this could be a help.  Certainly for many benchmarks
> it doesn't seem to matter.  However, this supposedly helps Java
> performance a lot, and maybe better compilers will help in teh future?
> 
> Personally, I'm with Aaron - for the desktop I wouldn't bother with
> a 64-bit OS today, unless i had need & budget for huge amounts of
> memory (photoshop or video editing come to mind).  
> 
> But of course Raymond is right, there's not much choice other than
> to buy 64-bit CPUs.
> 
> danno
> --
> dan pritts
> danno at umich.edu