New server advice - quad core any special settings needed?

[Gavin McCullagh]

Hi,

On Wed, 29 Aug 2007, Krsnendu dasa wrote:

> I'll be starting with 4 GB of RAM, (possibly increasing it in future.) Which
> kernel should I use?

As 32-bit machines usually address memory on a 32-bit address space, if you
have more than 2^32 bits of memory (about 4GB), you run out of addresses
and can't use the remaining RAM.  Actually, PCI devices must also be mapped
into the 32-bit address space which usually leaves you with more like
3-3.5GB).

If you're using a 32-bit kernel, you can either use:

  - the -generic- which will usually use a little over 3GB (4GB minus some
    address space used by the pci devices)

  - the -server-  which should use the full memory (using PAE), but at some
    processing cost
	http://www.spack.org/wiki/LinuxRamLimits

If you use a 64-bit kernel, just using the standard -generic- kernel will
allow you to address 2^64 bytes, so you don't need to worry about memory
limits.  The only thing is that fully 64-bit systems are relatively new and
still have some issues, usually with proprietary software (eg. there is no
adobe flash plugin or acrobat reader for 64-bit).  You can if you wish do
more complex things to run 32-bit apps on a 64-bit system.

	https://help.ubuntu.com/community/32bit_and_64bit
	http://www.phoronix.com/scan.php?page=article&item=616&num=1

I'm not sure what the issues are with WINE and 64-bit but it seems likely
a 32-bit windows app will need to run in 32-bit mode on linux.

Gavin