Atom 330 drives only enough pins for 32-bit physical addresses

[Lennart Sorensen]

On Fri, Nov 05, 2010 at 02:22:28PM -0400, D. Hugh Redelmeier wrote:
> | From: Mike Kallies <mike.kallies-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org>
> 
> | Strangely, if it shipped with Windows XP, people are used to only seeing
> | 3.25G when they're promised 4GB.  They can blame the OS.
> 
> It shipped with WIn7 home premium 64-bit.  So they cannot blame the OS
> (some support folk tried anyway).
> 
> Win7 says 4.0 G of RAM, 3.0 available.  The shared video memory
> accounts for 0.25G on top of that.  So 0.75G is missing.
> 
> | If you load Linux, they can say that the OS is not supported.
> 
> Oh yeah.  I told them that I booted a live Linux CD and they demanded
> that I reinstall Win7 to fix Win7 in case I had broken it.  With a
> live CD!

Well they get what they pay for in support people, which is not much.

> Linux sees 3.25G which, with the 0.25G shared video memory, leaves
> 0.5G missing (based on reading the MTRRs).  I don't know why Linux
> sees more than Windows.
> 
> | From: Lennart Sorensen <lsorense-1wCw9BSqJbv44Nm34jS7GywD8/FfD2ys at public.gmane.org>
> 
> | The Atom 330 mobile versions are only 32bit capable.  Desktop editions
> | can do 64bit.  Who knows which one acer used in their box.  A 32bit
> | version would only do up to 4GB address space after all.
> 
> This is non-mobile: it runs x86-64 software (Win7 and Linux).
> 
> Even 32-bit hardware, since the Pentium Pro, has had PAE to allow more
> that 32-bit physical addresses.  I imagine that this hardware has PAE
> but just doesn't drive the pins.

I am not sure if that atom uses a chipset for memory controller or if
it has it onboard.  Certainly the earlier atoms used chipsets for it
and those were generally older style low end laptop chipsets that were
limited to 4GB address space and didn't support remapping above 4GB.
Intel annoyingly took forever too get around to adding remapping to
desktop chipsets, while AMD had it early on.

> | As for what Acer advertises, well it does have 4GB ram installed.
> | The fact you can't use it all is a different issue. :)
> 
> I would call it misleading.

Sure.

-- 
Len Sorensen
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