Re: Opteron box and 4Gb memory

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From: J.A.
Date: Thursday, October 25, 2007 - 3:44 pm

On Thu, 25 Oct 2007 14:58:10 -0700, "H. Peter Anvin" <hpa@zytor.com> wrote:


I have collected several pieces of info around the internet...

- Some people uses this options in the BIOS:
	Node interleave: off
	Bank interleave: auto
	SW memory hole: disable
	HW memory hole: enable
	MTRR: Continuous

- Node Memory Interleaving DISABLES NUMA and generally is a bad thing

- MTRR setting -should be set to "discrete" for Linux, and probably for Windows too.

- This is what SuperMicro's tech support said about 2.96GB vs. 4GB.

"This is as expected, as soon as you set "software memory hole" to disabled,
you also disable option ROM remapping functionality, this option normally
remaps used option rom (option rom= raid bios, lan pxe ; usb legacy, bioses
on add-on cards, etc) in the 4GB region, so no basis memory is lost, while
this feature is now disabled the option rom space occupies the space between
3 and 4 GB which results in lower main memory availability.
There is no solution or work around for this phenomenon"

so software memory hole enabled might be needed to get all 4GB to show up

From mobo manual:

Software Memory Hole
When "Enabled", allows software memory remapping around the memory
hole. Options are Enabled and Disabled.

Hardware Memory Hole
When "Enabled", allows software memory remapping around the memory
hole. Options are Enabled and Disabled. Note: this is only supported by
Rev E0 processors and above.
( I have two Opteron 275 processors, no idea about revision)

So _my_ conclussion is:

	Node interleave: off    (numa mode)
	Bank interleave: auto
	SW memory hole: disable |
	HW memory hole: enable  | allow remapping
	MTRR: Discrete          |

But then, do I need to enable NUMA options in the kernel ?


I run a 64 bit one, then I don't need anything, isn't it ? That's why I
don't see any _HIGHMEM in the kernel configs...

Some day I will understand this crappy BIOS thing (or burn a photo of its
inventor...).
Why can't we have OpenFirmware PC's, like my MacPro  and Sparcs ?

--
J.A. Magallon <jamagallon()ono!com>     \               Software is like sex:
                                         \         It's better when it's free
Mandriva Linux release 2008.1 (Cooker) for i586
Linux 2.6.23-jam01 (gcc 4.2.2 20070909 (4.2.2-0.RC.1mdv2008.0)) SMP PREEMPT
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Messages in current thread:
Opteron box and 4Gb memory, J.A. Magallon, (Thu Oct 25, 2:09 pm)
Re: Opteron box and 4Gb memory, H. Peter Anvin, (Thu Oct 25, 2:58 pm)
Re: Opteron box and 4Gb memory, J.A. , (Thu Oct 25, 3:44 pm)
Re: Opteron box and 4Gb memory, Rafael J. Wysocki, (Thu Oct 25, 3:45 pm)
Re: Opteron box and 4Gb memory, Arne Georg Gleditsch, (Fri Oct 26, 1:08 am)
Re: Opteron box and 4Gb memory, J.A. , (Sun Nov 4, 4:18 pm)
Re: Opteron box and 4Gb memory, Lennart Sorensen, (Mon Nov 5, 11:10 am)
Re: Opteron box and 4Gb memory, J.A. , (Mon Nov 5, 11:45 am)
Re: Opteron box and 4Gb memory, Lennart Sorensen, (Mon Nov 5, 11:50 am)
Re: Opteron box and 4Gb memory, J.A. , (Mon Nov 5, 4:03 pm)
Re: Opteron box and 4Gb memory, Lennart Sorensen, (Thu Nov 8, 11:08 am)