[ubuntu-uk] ubuntu-uk Digest, Vol 72, Issue 11

Lee Williams lee.willy1977.williams at gmail.com
Thu Apr 7 14:55:17 UTC 2011

On 07/04/2011 15:28, Dave Hanson wrote:
> On 07/04/11 14:04, ubuntu-uk-request at lists.ubuntu.com wrote:
>> On 7 April 2011 13:54, Lee Williams<lee.willy1977.williams at gmail.com>  wrote:
>>> >  It's not a problem installing 32bit on a machine with>  ~3.5GB ram... rather
>>> >  the memory after the ~3.5GB or so is not "dedicated to system resources";
>>> >  rather, system resources have used up the remaining memory*addresses*, so
>>> >  the memory cannot be seen nor used by anything, as it has no address. When
>>> >  2GB RAM is installed, system components taking up 1GB or so of addresses has
>>> >  no effect, as there are 4GB of addresses in total, meaning 3GB of addresses
>>> >  are left available for the 2GB of RAM.
>>> >
>> I had to read that a few times, and it still makes no sense.
>> Fact is an install of Ubuntu on 32-bit system_can_  see and_use_  all
>> of the RAM.
>> Al.
> I run 8gb of ram on my laptop (64 Bit) and Ubuntu recognises 7.5gb of 
> it, Not too sure what you guys are getting at to be honest.
> Won't he be fine with the amounts he intends to add?
> Dave


Sorry if I've caused confusion.

I've not tested it with Ubuntu but a kernel running with PAE (Physical 
Address Extension) supported and enabled on a processor that supports 
PAE too will allow a user to have up to ~64GB of memory and the system 
will see and use all of that.

The ~4GB limit is an historic limit for 32bit processors due to the 
memory addresses available to it... however see 
http://en.wikipedia.org/wiki/Physical_Address_Extension for more 
information on what PAE does to get around it.

PAE is not needed with a 64 bit processor on 64bit implementation on 
your OS as the memory addresses available bring the "limit" up to if I 
remember correctly around 256TB... :o

Hope that clarifies it, again sorry if I've caused confusion.


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