Lubuntu, PAE, and 4GB of memory

Ben Coleman oloryn at
Sat Mar 21 19:06:25 UTC 2015

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 Coleman oloryn at | For the wise man, doing right trumps     | looking right.  For the fool, looking
Amateur Radio NJ8J              | right trumps doing right.

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