Re: x86 vs. x86_64

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Author: Stephen
Date:  
To: Main PLUG discussion list
Subject: Re: x86 vs. x86_64
Do not forget there is a limitation in chipset that will be needed to
use 4g of more of ram in a 32 not OS



On 3/25/10, Kurt Granroth <> wrote:
> Just to be pedantic; Matt is correct in his use of 'AND' with the
> memory. It is 'have more than 4GB RAM *AND* something that can use more
> than 4GB in one process'.
>
> Basically, this is due to PAE. The PAE extension (which all modern CPUs
> support) allow the OS to access up to 64GB of memory, even on a 32-bit
> x86 system. There's no need for a 64-bit processor for that.
>
> HOWEVER, PAE doesn't permit a single process from mapping or allocating
> more than 4GB. That's where you'll need 64-bit processors.
>
> And if you don't know for sure that you need that capability... then you
> definitely don't. It's very very rare (unless, of course, you are in
> the fields that do need that and then you'd know that).
>
> On 3/25/10 5:38 PM, Stephen wrote:
>> this is pretty accurate. if you are at the 4g limit or more then 64
>> bit. or if you are doing some really high end memory intensive
>> applications then you will have a need, otherwise 32 bit is the better
>> idea for compatibility and ease of use (some weirdness with flash in
>> 64 bit, solvable but you have some hoops to jump, there are a few
>> others like this)
>>
>> On Thu, Mar 25, 2010 at 3:32 PM, Matt Graham<>
>> wrote:
>>> From: Nathan England<>
>>>> Before I spend any time downloading and trying it myself, has any one
>>>> taken
>>>> the time to compare performance differences in every day usage between
>>>> ubuntu x86 and the 64 bit version?
>>>
>>> There is essentially ZERO performance difference between 64- and 32-bit
>>> Linux
>>> for normal user apps AFAICT on a Gentoo box. Couple that with the fact
>>> that
>>> at least one app (epsxe, PSX emulator) doesn't work at all on 64-bit
>>> Linux,
>>> and it's a no-brainer: Use 32-bit.
>>>
>>> The only reason that I can see to use 64-bit Linux is if you have more
>>> than 4G
>>> RAM in your box AND you've got something that can benefit from
>>> malloc()ing
>>> more than 4G of RAM in one process. So if you're running a big DB or a
>>> huge
>>> numerical simulation or something like that, go 64-bit. Otherwise, go
>>> 32-bit.
>>>
>>> (Constructive criticism and flying attack porcupines welcomed, since the
>>> above
>>> post may be full of bovine feces....)
>>>
>>> --
>>> Matt G / Dances With Crows
>>> The Crow202 Blog: http://crow202.org/wordpress/
>>> There is no Darkness in Eternity/But only Light too dim for us to see
>>>
>>>
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>>
>>
>>
>
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--
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Stephen
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