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List:       freebsd-amd64
Subject:    Re: More than 4 GBytes RAM on Socket939 system?
From:       "David O'Brien" <obrien () freebsd ! org>
Date:       2005-02-24 2:39:42
Message-ID: 20050224023942.GA39443 () dragon ! nuxi ! com
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On Wed, Feb 23, 2005 at 12:02:29PM -0700, Scott Long wrote:
> O. Hartmann wrote:
> > > >AMD64 processores only address 4 memory slots and can not address
> > > >128MBit memory chips,
> > >
> > >What is a 128 MBit chip?
> >
> >I found this info on ASUS homepage for the A8N-SLI and it means (I think)
> >a single IC, 128MBit x 8 organized.
> 
> I guess you're implying that the memory controller on the 939 only has
> enough address decode and refresh logic to drive DRAM chips of a certain
> maximum size?  David, can you comment?

I don't know enough about the ?weirder? DIMM organizations to comment.

I can say that a 939-pin Athlon64 has a dual-channel memory controller.
If only one of the dual-channels is populated, one does 64-bit accesses.
If both channels are [evenly] populated, one does 128-bit accesses.
One can use 2GB non-registered DIMM's in a 939-pin Athlon64 system.
4GB DIMM's don't exist in the desktop(workstation) space yet, so I won't
comment on them.  From an address-line POV, they will work fine.  From an
electrical POV maybe there could be issues if manufacturers push the JEDEC
spec beyond its limits.

-- 
-- David  (obrien@FreeBSD.org)
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