PaulNM grabbed a keyboard and wrote:
>
>
> On 12/12/2013 02:11 AM, David Guntner wrote:
>> Scott Ferguson grabbed a keyboard and wrote:
>>> On 12/12/13 17:42, erosenberg@hygeiabiomedical.com wrote:
>>>> Dear List -
>>>>
>>>> I am running 32 bit sid with a pae kernel. What is the maximum RAM that
>>>> can be used?
>>>
>>> 64GB
>>
>> Really? As I understand it, a 32-bit operating system cannot address
>> more than 4G of memory.
>>
>> What am I missing here?
>
> You're missing that it's a complete fallacy. Pretty much any processor
> from the Pentium Pro and up support PAE, and thus 64GB of RAM. Microsoft
> decided not to support that on the 32-bit versions of their consumer
> operating systems, but there's no technical reason preventing a 32-bit
> OS from using more than 4GB. (I mention MS because that's where most
> people I talk to get this idea from.)
>
> Provided the motherboard supports it, that is. :)
Gotcha. :-)
Ah, ok. While, yes, MS decidedly doesn't support it, I was actually
thinking in terms of 32-bit addressing - which *would* only support up
to 4GB. Thanks for the mention of PAE; I did a quick search on it and
found the following at Wikipedia:
"In computing, Physical Address Extension (PAE) is a feature to allow
32-bit x86 central processing units (CPUs) to access a physical address
space (including random access memory and memory mapped devices) larger
than 4 gigabytes.
"First implemented in the Intel Pentium Pro in 1995, it was extended by
AMD to add a level to the page table hierarchy, to allow it to handle up
to 52-bit physical addresses, add NX bit functionality, and make it the
mandatory memory paging model in long mode.[1] PAE is supported by Intel
Pentium Pro and later Pentium-series processors except most 400 MHz-bus
versions of the Pentium M.[citation needed] It is also available on AMD
processors including the AMD Athlon and later AMD processor models."
And it went on in all kinds of details from there.
So there are some nifty hardware tricks that let you get around the
limitation. Good stuff! :-) Thanks for the info.
--Dave
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