[clug] OT: DDR RAM and FSB speed

Duncan Roe duncan_roe at acslink.net.au
Sun Feb 6 03:38:08 GMT 2005

Hi Darren,

It seems the BIOS is reserving that last 0.5GB(!)

This is the reply from MSI tech support:-

>! From: ERIC MSI [mailto:eric at msicomputer.com.au]
>! Sent: Thursday, 27 January 2005 12:32 PM
>! To: Vincent - MSI
>! Subject: Re: Still only see 3.5G RAM (was: BIOS URL)
>! In 4GB configurations the visible memory may be reduced down to 3.5GB
>! depending on your system configuration. Under current PC memory
>! addressing, there is a memory area (of approximatley 0,5GB) which is
>! reserved permanently. The reserved area is for the system BIOS to store
>! APIC, ACPI Table, PCI Devices', Resources and AGP aperture information.
>! If the system DRAM is above 3.5GB of memory, the actual amount of memory
>! that the system shows will be less due to this reserved area. Regardless
>! of memory size, the reserved memory addressing is always present, but
>! only when the DRAM rises above the 3.5 GB will that area become visible.
>! The available memory size may be less than 3.5GB if for example a PCI
>! card needed more memory. eg. for large Graphics AGP Aperture size.

I replied suggesting it was about time this legacy BIOS feature was updated - no

I know, I've read "Never buy MSI" on this list before. But I like the board
otherwise. Just wish they would fix the BIOS.

Cheers ... Duncan.

On Thu, Feb 03, 2005 at 12:33:54PM +1100, Darren Freeman wrote:
> On Fri, 2005-01-28 at 08:13, Duncan Roe wrote:
> > Hi Darren,
> >
> > Just checking - are you saying DDR400 & PCI3200 are different?
> No they're the same. Only it's PC3200 not PCI3200.
> > I was told emphatically by the PC shop that they were the same, but I'm having a
> > problem with my dual Opteron - BIOS only sees 3.5G with all 4 sticks in but sees
> > 2G with any 2 in. Tech support said to upgrade to latest BIOS which I did, but
> > the problem persists.
> Perhaps you are running them in 32bit mode? 32bit addressing hits a
> limit at 4GB. Leaving room for other memory-mapped peripherals, I can
> see why this might happen. But in 64bit mode it shouldn't have this
> problem, at least at the CPU level anyway, and I hope they haven't done
> anything weird in the motherboard.
> I've never touched an SMP machine so I don't know if there are issues
> with the two CPUs each controlling two sticks and then having trouble
> sharing the memory between them. Or whatever.
> > Cheers ... Duncan.
> Have fun,
> Darren

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