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Old 08-15-2011, 01:02 AM   #1
EDDY1
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What's the difference between regular kernel & pae


I recently installed 3.0 pae kernel on my debian machine, it comes with many errors that are corrected before boot, so they're not logged.
I understand that pae is Physical Address Extension, but don't understand the benefits of pae on a laptop with intel celeron (M) processor
 
Old 08-15-2011, 01:13 AM   #2
Wim Sturkenboom
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The advantage I'm aware of is support for > 3GB memory in the PAE
 
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Old 08-15-2011, 01:29 AM   #3
EDDY1
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My laptop only suppports 2gig, so there is no adavantage?
My amd64 no problem my intel 32-bit spits errors

Last edited by EDDY1; 08-15-2011 at 01:33 AM.
 
Old 08-15-2011, 04:20 AM   #4
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On 64 bit kernels PAE has no function, disable it (shouldn't be there by default, in the first place, IIRC).
On 32 bit systems it is only useful if you have more than 3 GB of RAM.
 
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Old 08-16-2011, 11:59 PM   #5
EDDY1
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Thank you for the information.
Quote:
On 64 bit kernels PAE has no function, disable it (shouldn't be there by default, in the first place, IIRC).
It's an installation within virtual box where I test different Os'es
Quote:
On 32 bit systems it is only useful if you have more than 3 GB of RAM.
Since the 32-bit system only supports 2Gigs ram should I disable the pae here also?
 
Old 08-17-2011, 07:49 AM   #6
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Quote:
Originally Posted by EDDY1 View Post
Since the 32-bit system only supports 2Gigs ram should I disable the pae here also?
Simple as that: If you don't use it (and you won't on a system with 2GB RAM), don't enable it.
 
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Old 08-17-2011, 08:29 AM   #7
EDDY1
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Thank you TobiSGD
 
Old 08-17-2011, 09:27 AM   #8
johnsfine
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Quote:
Originally Posted by EDDY1 View Post
I understand that pae is Physical Address Extension, but don't understand the benefits of pae on a laptop with intel celeron (M) processor
You have "Wins7" in the list in your signature, so I wondered if your question was limited to Linux or also included Windows.

The PAE hardware feature includes both physical address extension and data execute protection.

The easiest ways to exploit stack and buffer overflows involve executing data. If the OS and hardware enable data execute protection, that whole class of vulnerability goes away. In Windows, that is an important protection. If you enable PAE in 32 bit Windows, despite having only 2GB of ram, you eliminate some of the ways that web sites and emails can take over your computer.

I think PAE in 32 bit Linux also enables hardware data execute protection (but I'm not actually sure of that). But many skilled programmers review open source browsers and email clients looking for the errors that could be exploited when you don't have data execute protection. Those get reported and fixed. So data execute protection is a lot less important if you are using open source browsers and email clients.

Quote:
Originally Posted by EDDY1 View Post
My amd64 no problem my intel 32-bit spits errors
Are you talking about OS's or CPU's or what?

An AMD64 architecture OS has no PAE option. There is nothing about PAE to enable or disable. So I don't understand any mention of it in a PAE question.

The hardware features (including data execute protection) that are called "PAE" in 32-bit mode are unconditionally enabled in 64-bit mode. They aren't called "PAE" in 64-bit mode and there is no option to turn them off in 64-bit mode.

Quote:
Originally Posted by EDDY1 View Post
Since the 32-bit system only supports 2Gigs ram should I disable the pae here also?
In 32-bit Linux, PAE is an option at the time you compile the kernel, not at the time you start the OS. Maybe that is what you meant by "disable", but it sounds more like the way one would describe things in 32 bit Windows, where you can enable or disable PAE when you boot the OS.

Last edited by johnsfine; 08-17-2011 at 09:34 AM.
 
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Old 08-17-2011, 12:41 PM   #9
EDDY1
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@johnsfine
Quote:
Quote:
Quote:
Originally Posted by EDDY1 View Post
My amd64 no problem my intel 32-bit spits errors
Are you talking about OS's or CPU's or what?

An AMD64 architecture OS has no PAE option. There is nothing about PAE to enable or disable. So I don't understand any mention of it in a PAE question.
When I mentioned amd 64, I was a bit unclear in my explanation,
My main os is Debian squeeze 64bit, but in testing the 3.0 kernel, I did it in virtualbox on debian testing which is 32bit, I did not compile the kernel I did a distro upgrade & that is the kernel that was installed. After upgrade I noticed pae extension, the kernel gave no errors so, I decided to try on my laptop, where I found that there were some issuses with laptop_mode functions as it attempts to load drivers too early, but they load. Also had to edit laptop_mode file to include the 3.0 kernel.

Quote:
You have "Wins7" in the list in your signature, so I wondered if your question was limited to Linux or also included Windows.
Yes it's on it's own hdd, when I built my machine I didn't think that I would ever have a stable os, but who new that Debian would work so well for me.

Last edited by EDDY1; 08-17-2011 at 12:48 PM.
 
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