Re: Only 3.2G ram out of 4G seen in an i386 box

["gmu 2k6" <gmu2006@gmail.com>]

On 8/10/06, Simen Thoresen <simentt@dolphinics.no> wrote:
> gmu 2k6 wrote:
> ...
> > so what does it mean that one of Xeons here shows me the full 4GiB as
> > total physical memory via `free`?
> >
> > btw, the box I'm getting will have the 975X chip and include 4GiB RAM
> > and if I understood the problem correctly even with 3GiB there will be
> > some memory lost to mapping-issues besides the HI/LO mem
> > kernel-reserving issue.
> > this is what I get on ia32 P4 with 3GiB
> >             total       used       free     shared    buffers     cached
> > Mem:       3116108    2608196     507912          0     246652    2039708
> > and this is what I get on ia32 Xeon with 4GiB
> >             total       used       free     shared    buffers     cached
> > Mem:       4087660     268828    3818832          0      57168     103568
>
> Hi Gmu,
>
> This is a bit divergent from the discussion, but will hopefully provide some
> background.
>
> The hardware my employer manufactures asks the BIOS to reserve several
> largeish ranges (16M and 16M to 512M), and it's been used in various HPC
> projects where machines typically have a lot of memory installed.
>
>  From my experience, most pre 750x-P4-Xeon chipsets did not support any kind
> of memory remapping, so often the top 0.5-1.5G of ram would be 'lost'. Great
> fun.
> Since then, this functionality has started appearing, more or less randomly.
> I believe it should be present on all later 75xx chipsets (probably the Core
> 2 Xeon chipsets as well), but implementation depends on the BIOS (ie the
> motherboard vendors), and their grasp of what people do with their boards is
> often quite limited.
>
> On the P4 boards (and again the Core 2 boards as well), this is probably
> even less ordered as they are 'desktop' boards rather than the more costly
> 'server' boards.
>
> I'm pretty sure the Athlon64 and Opteron CPUs should support this, but they
> too depend on BIOS functionality to rearrange the memory tables.
>
> Just out of interest - what chipset does your Xeon system use?

lspci of the P4 32bit desktop with 3GiB
00:00.0 Host bridge: Intel Corporation 82875P/E7210 Memory Controller
Hub (rev 02)
00:01.0 PCI bridge: Intel Corporation 82875P Processor to AGP
Controller (rev 02)
00:1d.0 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB
UHCI Controller #1 (rev 02)

lspci of the Xeon 32bit HP Proliant Server with 4GiB:
00:00.0 Host bridge: Intel Corporation E7520 Memory Controller Hub (rev 0c)
00:02.0 PCI bridge: Intel Corporation E7525/E7520/E7320 PCI Express
Port A (rev 0c)
00:06.0 PCI bridge: Intel Corporation E7520 PCI Express Port C (rev 0c)
00:1d.0 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB
UHCI Controller #1 (rev 02)

lspci of the new box with 975X and Core 2 Duo not available yet for
obvious reasons (I don't have the the box yet).
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