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From "Ronald Klop (Mailing List)" <ronald-mailingl...@base.nl>
Subject Re: [OT]RE: Maximum memory that can be assigned to Tomcat on windows platform
Date Thu, 01 Dec 2011 11:05:33 GMT



Op donderdag, 1 december 2011 09:39 schreef Casper Wandahl Schmidt <kalle.privat@gmail.com>:
> 
>   
>  See below. I hope MS Outlook does some decent indend so my response is clear -.-
>  
>  -----Original Message-----
>  From: Christopher Schultz [mailto:chris@christopherschultz.net]
>  Sent: 30. november 2011 18:51
>  To: Tomcat Users List
>  Subject: Re: Maximum memory that can be assigned to Tomcat on windows platform
>  
>  -----BEGIN PGP SIGNED MESSAGE-----
>  Hash: SHA1
>  
>  Casper,
>  
>  On 11/30/11 3:37 AM, Casper Wandahl Schmidt wrote:
>  > Another question to ask is, why do you have 8GB memory when running
>  > 32bit? That is just stupid since 32bit cannot address more than 4GB of
>  > memory no matter what you do. Any sysadmin should know that right?
>  
>  That's per process. All reasonably recent 32-bit OSs can address way more than 4GiB
internally.
>  
>  For example:
>  http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778%28v=vs.85%29.aspx#memory_limits
>  
>  This is generally done through PAE
>  (http://en.wikipedia.org/wiki/Physical_Address_Extension) which allows 32-bit OSs to
access more than 4GiB at the kernel level, though each process is still limited to 4GiB.
>  
>  Aha so I learned something new today :) I'm still puzzled as to how a 32 bit CPU can
compute and fetch a memory cell with address above 4GB since it cannot hold this large value.
Anyway that is just too much low-level computer science for me, all I ever had was a seven
week course on architecture and networking (a single week out of the seven) :)
>  
>  -Casper
>  
>  Running a machine with more than 4GiB in 32-bit mode isn't stupid at all IMO. If you
have relatively small processes, there's no need for the overhead of 64-bit even if you have
16GiB or more.
>  
>  - -chris
>   
>  
> 
> 
>   
 I have an analogy for you.
 If you look out of your window you only see a small part of the world. If you move your window
you wil see another part of the world.
 This is what the OS does with PAE. It moves the window on your RAM frequently. That is why
a 32 bits application only sees max. 4GB. That is the size of its window.

 Ronald.
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