Lubuntu, PAE, and 4GB of memory

Andre Campos Rodovalho andre.rodovalho at gmail.com
Sun Mar 22 01:01:54 UTC 2015


Some BIOS are limited to 3.25G RAM. This might be your case... The 32bit
systems are limited to 4Gb. 32 bits in theory can handle 4Gb, but sometimes
not practically...
AFAIK PAE is enabled automatically when the processor has this
capability... You can disable it or force it with kernel parameters.


2015-03-21 16:06 GMT-03:00 Ben Coleman <oloryn at benshome.net>:

> On 3/20/2015 20:19, Andre Campos Rodovalho wrote:
> > Are you using a 32 bit operating system and/or hardware??
> The CPU is 32 bit, but PAE-capable.  I'm running 32-bit Lubuntu 14.10.
>
> For testing purposes, I popped out one of the 1GB memory sticks and put
> in a 256MB in it's place, giving the machine a total of 3.25G RAM.  Free
> still shows the same amount of Total memory as with 4GB of RAM.  This
> tells me that at least 768MB of RAM is going unused when I've got the
> full 4GB in there.
>
> The BIOS has a couple of settings for video-related memory access;
> Onboard Video Buffer (which may be irrelevant as I'm not using the
> Onboard Video) can be switched between 1 and 8MB; AGP Aperture can be
> set between 32MB and 256MB.  Changing either of those settings makes no
> difference in what free shows as max memory.
>
> lshw shows memory size as 4GiB, so on *some* level the full memory size
> is being seen.
>
> I do realize that in a 32-bit memory space, *some* of that memory space
> has to be reserved for non-RAM system purposes, but it's my
> understanding that PAE effectively produces a 36-bit memory space.
> Either I'm misunderstanding the effect of PAE on that 'reserved' memory
> space, or PAE isn't being used.  I'm wondering if it's the latter, and I
> need to do something to have PAE be used.
>
> Ben
> --
> Ben Coleman oloryn at benshome.net | For the wise man, doing right trumps
> http://oloryn.benshome.net/     | looking right.  For the fool, looking
> Amateur Radio NJ8J              | right trumps doing right.
>
>
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