****Re: ****Re: ****What's up with 64 bit Linux

[Chris Gehlker]

On Nov 22, 2007, at 10:32 PM, Craig White wrote:

> On Thu, 2007-11-22 at 18:46 -0700, Chris Gehlker wrote:
>> On Nov 22, 2007, at 5:49 PM, Jon M. Hanson wrote:
>
>> I readily admit that what I can easily find on the web corresponds to
>> the "Compatibility mode can only be set at boot time so it's not
>> something you can switch back and forth while the system is running"
>> model that you lay out above and that model is perfectly consistent
>> with what Craig reports. Something is missing though. These machines
>> can run either 32 or 64-bit Windows but only 64-bit Linux. It doesn't
>> make sense.
> ----
> but that isn't what I said at all.
>
> It's not that 32 bit Linux can't run on these systems...it's that the
> code within the i386 kernel and modules doesn't work properly and I am
> reliant upon open source developers, mainly kernel developers to work
> through the issues presented by this specific hardware.
>
> The fact is that even on the 64 bit versions, there has been  
> regression
> within Fedora 7 which used a 2.6.21 kernel when released and the last
> update used a 2.6.23 kernel and now the systems no longer poweroff  
> when
> instructed to shut down (not a big deal but a minor nuisance).
>
> The 2.6.23 kernel used on Fedora 8 is even worse for this specific
> hardware. That hardware is not available with Windows XP
> pre-installed...only Vista. Obviously there is some support for this
> hardware within Windows Vista that isn't incorporated into 2.6.23
> kernels (yet at least, perhaps in a test kernel that I am not aware  
> of).


OK, So your experience is that i386 runs but not as well as i86_64.  I  
notice from that link you cited that the Fedora folks recommend the  
opposite approach.
>
>
> As for 64 bit Windows...it's there but few are using it because it  
> is so
> incredibly buggy that you have to be a martyr to use it so I'm told.
>
> It's easy enough to boot a 64 bit Linux and run 32 bit versions of
> programs provided that you have the library support to do so. Many
> choose to do that for things like Firefox so they can use 32 bit only
> versions of plugins such as Adobe's Flash and Acrobat Reader.

OK then Jon's information about having to pick a mode at boot time is  
wrong. But the real problem here is that while the advantages of  
running 64-bit apps on a 32-bit OS are clear, there aren't any  
advantages to doing it the other way around.
>
>
> I just wanted to point out that you are drawing conclusions that I  
> don't
> believe are supported by my own experiences.
>
> Looking at this matrix that is part of Fedora 8 installation
> documentation,
> http://docs.fedoraproject.org/install-guide/f8/en_US/sn-which- 
> arch.html
> it's pretty clear that they are recommending installation of the 86_64
> version for all Intel Core 2 Duo, Centrino Core 2 Duo, Xeon and AMD 64
> processors.

Yes. But they don't say why. When I took an operating systems class,  
not that long ago the goal was clearly to avoid 64-bit code whenever  
possible because it page faults more. Of course now that I look again  
at the referenced page, it doesn't say that x86_64 is actually 64-bit  
code.I could be mostly 32_bit code optimized for 64-bit processors.

--
A young idea is a beautiful and a fragile thing. Attack people, not  
ideas.