Re: Problems with AMD64 and 8 GB RAM?

From: Scott Long (scottl_at_samsco.org)
Date: 03/31/05

  • Next message: Scott Long: "Re: Problems with AMD64 and 8 GB RAM?" 
    Date: Wed, 30 Mar 2005 16:21:23 -0700
To: "Greg 'groggy' Lehey" <grog@FreeBSD.org>

    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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  • Next message: Scott Long: "Re: Problems with AMD64 and 8 GB RAM?"

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