On 10/17/2011 09:50 AM, Stephan Wiesand wrote:
> On Oct 17, 2011, at 18:20 , Yasha Karant wrote:
> [...]
>> Now I have a decision to make:  IA-32 SL 6.1 or X86-64 SL 6.1 .  The processor will support X86-64, but the machine only has 4 Mbyte of RAM as delivered (upgradeable to 8 Mbyte -- but this is a cost) -- which is only 0.5 Mword in X86-64 64 bit mode.  The hard drive is 500 Gbyte SATA at 5400 RPM -- not a high performance unit.
>
> I guess we're talking Gigabytes of RAM here, not Megabytes?
>
>> There is no special need for 64 bit work on the machine that primarily is an end-user linux workstation: web browser (including use of university services only available through such an interface), IMAP email client, OpenOffice, various LaTeX interfaces, some display of video, use of Linux VirtualBox to use MS Win (for which the unit is licensed) to use a MS Win only application, but no development or programming -- and the ability for a skilled end user under Network Manager to connect to whatever 802.11 WAP that is available without my intervention.
>>
>> Thus, my feeling is to stay with the IA-32 environment.  Any thoughts to the contrary?
>
> Yes: The 32-bit kernel will leave 25% of your 4 GB RAM unused, I believe. And all processes will be confined to 3 GB of address space (even if purely virtual). Increasingly, new features are only made available by TUV for the 64-bit flavour (KVM, xfs, samba3x on SL5, pNFS). Since the Java and Flash plugins are now available as 64-bit builds, much of the hassle with running 64-bit SL is now history. x86-64 has a future, ia32 IMHO hasn't (x32 seems interesting but will take a while to arrive and will use a 64-bit kernel). The extended register set and faster PC-relative addressing are not available to ia32 applications. A 500GB disk is plenty for installing the .i686 packages alongside the 64-bit ones.
>
> That being said, staying with ia32 may still be slightly more convenient, and part of the 1 GB of real memory you gain with x86-64 will be consumed by 64-bit pointers/longs and alignment.
>
> Choose your poison ;-)
>
> HTH,
> 	Stephan
>
>

You are correct; errors from too much late night work and too much 
multitasking.   4 Gbyte RAM as base, thus 1 Gword in IA-32 mode, and 0.5 
Mword in X86-64 64 bit mode.

I agree with the issue of "pick your poison", but none of the features 
you mention currently are needed by the end user on a simple client 
workstation.  I suspect that I shall continue to use and recommend 
VirtualBox until such time as the distro equivalent becomes more easily 
fully functional -- for a long time, I stuck with VMware until both the 
VMware license become onerous and VirtualBox had all of the essential 
functionality of VMware for the applications under which I use a virtual 
machine to run a guest OS (e.g., MS Win).  I am concerned that 0.5 Mword 
will not be sufficient and that there will be excessive swapping to the 
hard drive.

Although a migration from IA-32 SL 6 to X86-64 SL 6 does require a 
complete re-install, if one is careful with saving the various current 
(e.g., SL 6.current in both the IA-32 and X86-64 environments) IA-32 
libraries in the right places so that these can be put back in place 
under the X86-64 (e.g., mv the entire tree to a partition that will not 
be touched by the install, such as /home, and then cp back the contents 
to the correct location (e.g., /lib), the 64 bit environment should 
support 32 bit executables.

Yasha Karant