Date: Wed, 30 Mar 2005 16:21:23 -0700 From: Scott Long <scottl@samsco.org> To: "Greg 'groggy' Lehey" <grog@FreeBSD.org> Cc: Steve Kargl <sgk@troutmask.apl.washington.edu> Subject: Re: Problems with AMD64 and 8 GB RAM? Message-ID: <424B3473.9010108@samsco.org> In-Reply-To: <20050330231541.GZ84137@wantadilla.lemis.com> References: <20050330222439.GU84137@wantadilla.lemis.com> <20050330223546.GA4705@troutmask.apl.washington.edu> <20050330224445.GW84137@wantadilla.lemis.com> <424B2FBA.1020102@samsco.org> <20050330231541.GZ84137@wantadilla.lemis.com>
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Greg 'groggy' Lehey wrote: > On Wednesday, 30 March 2005 at 16:01:14 -0700, Scott Long wrote: > >>Greg 'groggy' Lehey wrote: >> >>>On Wednesday, 30 March 2005 at 14:35:46 -0800, Steve Kargl wrote: >>> >>> >>>>On Thu, Mar 31, 2005 at 07:54:39AM +0930, Greg 'groggy' Lehey wrote: >>>> >>>> >>>>>None of these problems occur when I use 4 GB memory. About the only >>>>>strangeness, which seems to come from the BIOS, is that it recognizes >>>>>only 3.5 GB. If I put all DIMMS in, it recognizes the full 8 GB >>>>>memory. >>>> >>>>I had 4 bad out of 12 tested where the DIMMs were Crucial PC2700 2GB >>>>Reg. ECC DIMMs. >>> >>>OK, this makes sense. It might also explain why the 4 GB >>>configuration only recognizes 3.5 GB. >> >>No, and I'm going to make this an FAQ and post it in a very obvious >>place, since 4+ GB is so easy to get and people don't seem to understand >>the PC architecture very well. > > > That's not easy to understand when it's barely documented. Thanks for > the info: it helps a lot. > > This may still be a hint, though: that memory hole doesn't show up > during a boot with 8 GB RAM. How come? Is the system trying to map > RAM over the PCI hole? > > It looks as if I should get a verbose boot listing with 8 GB. It'll > be a couple of hours before I find time to reboot this machine. In > the meantime, there's a verbose boot with 4 GB at > http://www.lemis.com/grog/Images/20050331/obelix-dmesg. I'm told it > shows a number of strange things, including incorrect reporting of > on-chip cache sizes. > The SMAP will show the hole. It's well documented in most PC archtitecure books. Scott
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