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Date:      Mon, 28 Feb 2005 11:48:57 -0800
From:      "David O'Brien" <obrien@freebsd.org>
To:        Roman Neuhauser <neuhauser@chello.cz>
Cc:        freebsd-amd64@freebsd.org
Subject:   Re: FreeBSD 5.3 installation on Asus K8V-D impossible?
Message-ID:  <20050228194857.GA59327@dragon.nuxi.com>
In-Reply-To: <20050228083319.GA379@isis.wad.cz>
References:  <25805.1109507962@www41.gmx.net> <20050228021220.GB13696@dragon.nuxi.com> <422289DB.5090408@sdodson.com> <4222A92E.6020500@gmx.net> <84dead72050227215243be0950@mail.gmail.com> <20050228073954.GA14037@isis.wad.cz> <20050228082523.GB38063@dragon.nuxi.com> <20050228083319.GA379@isis.wad.cz>

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On Mon, Feb 28, 2005 at 09:33:19AM +0100, Roman Neuhauser wrote:
> # obrien@freebsd.org / 2005-02-28 00:25:23 -0800:
> > On Mon, Feb 28, 2005 at 08:39:54AM +0100, Roman Neuhauser wrote:
> > >     What memory did you have in the box? I've had the same problem with
> > >     K8T Neo-FIS2R and 3x Corsair CMX512-3200C2. The board only works
> > >     with a narrow selection of 400MHz modules. :(
> > 
> > Actually I would read the mobo *and* AMD docs very, very carefully.
> > Using 3x DDR400 (PC3200) DIMM's is out of the JEDEC spec, IIRC.  I stick
> > to DDR333 (PC2700) memory as its easy to find CL2.5 DIMMs, but most
> > DDR400 is CL3.0.  So the end performance in the BW increase is mostly a
> > wash; and I avoid the electrical loading issues of the faster memory bus.
> 
>     I'll admit I'm not an expert on hardware, can you point out what's
>     wrong with the configuration (3 double-sided 400MHz modules)?

It is an electrical load issue.  The non-buffered memory controller can
only drive 2x DDR400 loads.  A 939-pin dual-channel memory controller
Athlon64 can drive 4x DDR400 loads.  An Opteron can drive more due to
being buffered/registered memory.
 
-- 
-- David  (obrien@FreeBSD.org)



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