Three out of Four Isn't Bad

[Roger Heflin]

Langdon Stevenson wrote:
> Roger Heflin wrote:
>> Néstor wrote:
>>> I have a situation where I have 36 Gigs of ram on a machine and I 
>>> could only
>>> see 4 Gigs
>>> then I installed the PAE kernel and I can only see 24 Gigs.  I have a 
>>> ticket
>>> opened with
>>> Red Hat to see what they recommend.
>>>
>>> :-)
>>>
>>
>> If that is a 64-bit capable machine, you should run 64-bit on it, you 
>> can run 32-bit userspace stuff, but if you run a 32-bit os with that 
>> kind of ram you run into all sorts of issues with the machine running 
>> out of the 800-900MB of lowmem and this causes fatal issues even those 
>> massive amounts of highmem are available.   You will have enough 
>> issues with 32-bit and lots of ram to make it worth considering the 
>> 64-bit stuff.
>>
>>                               Roger
> 
> 
> I recently upgraded from F7 to F8 and went with the 32 bit F8 version 
> rather than the 64 F7 due to the significant difficulties I had with 
> FireFox/Flash/Java.
> 
> I had installed another 2 Gig of RAM just prior to the upgrade and it 
> showed up fine under F7 64bit.
> 
> However on F8 32bit I can only see 3.2 gig of my RAM.  It is not a huge 
> problem as I don't use it all.  The 64 version of F7 used to gobble up 
> all of my RAM occasionally (I could never figure out why, or what 
> application was responsible).  That problem vanished with the 32 bit F8 
> and 32 bit apps.
> 
> It is interesting though that when the 64 v's 32 bit question has been 
> asked on this list that I have never heard this memory limit mentioned 
> (I may have missed it though).  Perhaps it is just that RAM is now 
> soooooo cheap that it is only just becoming an issue.
> 
> Still.  Looks like a really good reason to go with 64 bit next time I do 
> an upgrade!
> 
> Langdon
> 

Even with 64-bit OSes the desktop boards aren't setup to properly support 64bit 
OSes, mainly since they are used in 32-bit OSes (windows) if they remapped the 
memory properly for 64-bit OSes none of the remapped memory would be there for 
the 32-bit OSes.

The only significant difference between 32bit and 64bit is that 64bit can have 
greater then 3GB per process.   64 bit does have more registers, but often this 
is offset by having to load the 8-bit pointers from memory so there is little or 
no performance difference.

A 32-bit OS with PAE (linux kernel option) should see all of the ram that a 
64-bit OS can.   The best options are to run a 64-bit OS, but use 32-bit 
applications for things like firefox that require plugins that are only 
available in 32-bit.   It does take a small amount of messing around to get the 
install correct, but it is not that hard, the easiest way would be to just use 
the firefox.tar.gz download for 32-bit from firefox's web page.

                          Roger