# Reserve low 64K of RAM on AMI/Phoenix BIOSen

## Shining Arcanine

I was at my local Linux User's Group meeting this week and there was a presentation on how to compile your own kernel. I ended up giving half the presentation from my seat because no one knew what many kernel options did and they did not actually need to compile them. People also did not know how to properly tune the kernel. My only regret is that I forgot to tell people to disable the routing stuff because I doubt anyone there planned on having their laptop double for a L3 router.

Anyway, the guy giving the presentation had "Reserve low 64K of RAM on AMI/Phoenix BIOSen" off, so I mentioned it. He said that he has never had a problem with it off and suggested I try having it off, so I did and suspend/resume appear to work without an issue. I am not sure if this is because the kernel happened to not be using the low 64KB of RAM when I tried it or if it is because the BIOS bug was fixed a really long time ago and this option is there for legacy purposes.

Does anyone know whether or not this bug was fixed by Phoenix (in my case) before 2006?

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## Hu

 *Shining Arcanine wrote:*   

> Anyway, the guy giving the presentation had "Reserve low 64K of RAM on AMI/Phoenix BIOSen" off, so I mentioned it. He said that he has never had a problem with it off and suggested I try having it off, so I did and suspend/resume appear to work without an issue. I am not sure if this is because the kernel happened to not be using the low 64KB of RAM when I tried it or if it is because the BIOS bug was fixed a really long time ago and this option is there for legacy purposes.
> 
> Does anyone know whether or not this bug was fixed by Phoenix (in my case) before 2006?

 Git history shows that the configuration option appeared in x86: add X86_RESERVE_LOW_64K dated Tue Sep 16 10:07:34 2008 +0200.  It appears the reservation code itself was added in x86: add DMI quirk for AMI BIOS which corrupts address 0xc000 during resume dated Tue Sep 16 09:29:09 2008 +0200.  A quick scan of the bugs referenced in those commits leads to comment #109 from Ingo Molnar, which says in part: *Igno Molnar wrote:*   

> Both AMI and Phoenix BIOSes are affected, both old and new BIOSes. There's no good date cutoff and no good BIOS type and system type cutoff either.

 

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## gerard27

I now own an Asus MoBo with AMI Bios.

One thing:My next MoBo will have to have another bios.

AMI sucks.

Gerard.

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## Shining Arcanine

 *Hu wrote:*   

>  *Shining Arcanine wrote:*   Anyway, the guy giving the presentation had "Reserve low 64K of RAM on AMI/Phoenix BIOSen" off, so I mentioned it. He said that he has never had a problem with it off and suggested I try having it off, so I did and suspend/resume appear to work without an issue. I am not sure if this is because the kernel happened to not be using the low 64KB of RAM when I tried it or if it is because the BIOS bug was fixed a really long time ago and this option is there for legacy purposes.
> 
> Does anyone know whether or not this bug was fixed by Phoenix (in my case) before 2006? Git history shows that the configuration option appeared in x86: add X86_RESERVE_LOW_64K dated Tue Sep 16 10:07:34 2008 +0200.  It appears the reservation code itself was added in x86: add DMI quirk for AMI BIOS which corrupts address 0xc000 during resume dated Tue Sep 16 09:29:09 2008 +0200.  A quick scan of the bugs referenced in those commits leads to comment #109 from Ingo Molnar, which says in part: *Igno Molnar wrote:*   Both AMI and Phoenix BIOSes are affected, both old and new BIOSes. There's no good date cutoff and no good BIOS type and system type cutoff either. 

 

Thankyou for the information. I will turn this back on.

Does anyone know if there is an easy test to determine whether or not this option is strictly necessary?

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## gerard27

What diff will 64K make?

Better safe than sorry.

Gerard.

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