Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
On Thu, 09 Sep 2004 05:34:05 -0400, nospam@needed.com (Paul) wrote:
>In article <S4R%c.363557$gE.165616@pd7tw3no>, Philip Callan
><callanca@shaw.ca> wrote:
>
>> Paul wrote:
>> > In article <chn9lk$7rh$1@south.jnrs.ja.net>, Phil Vossler
>> > <p.j.vossler@exeter.ac.uk> wrote:
>> >
>> >
>> >>I've tried installing four sticks of 1Gb Crucial DDR modules in two of
>> >>these Asus motherboards and each time only 2.94Gb is recognized by the
>> >>system. Bios is v1016. The modules are those recommended by Crucial
>> >>(CT12864Z40B)
>> >>
>> >>Has anyone else had problems running this board with the maximum memory
>> >>possible? Conversely, has anyone had success with this board and the
>> >>recommended Crucial memory modules?
>> >>
>> >>First time I've ever had a problem using an Asus board...any assistance
>> >>appreciated...
>> >
>> >
>> > Page 118 of the 875P Northbridge chipset shows the memory map:
>> >
http://developer.intel.com/design/chipsets/datashts/25252501.pdf
>> >
>> > The Northbridge lives within a 4GB address space. AGP and PCI card
>> > requirements come out of the same memory space. The TOMM register
>> > in the Northbridge "punches a hole" in the DRAM, to make room for
>> > the rest of the memory map.
>> >
>> > To make more main memory available, try removing PCI cards,
>> > disabling unused PCI onboard devices, decrease the AGP aperture
>> > setting, use a PCI video card with small onboard memory, and maybe
>> > the free memory will be able to reach 3.5GB.
>> >
>> > HTH,
>> > Paul
>>
>> So you're saying that there is no difference between running 3 1G sticks
>> and running 4 on a 875P chipset? Does it take that RAM out of the
>> address space total (all 4G) or just the top (xMB) from real RAM I've
>> never noticed any reduction in total visible memory on any of these
>> boards I've installed 2GB on.
>>
>> Or will running the 4th stick just allow you to run all your (visible)
>> RAM in dual channel?
>
>For max economy, you could run 2x512+2x1024, and the two address
>spaces probably wouldn't bump into one another. Running 4x1024 minus
>at least 512MB for that PCI/AGP stuff, leaves you with 3.5GB on a
>good day, and unless you need that extra bit of ram badly, might not
>be a wise investment.
>
>When using 4x512, the 2GB from low memory space doesn't get to bump
>into the 512MB+ needed near the top end of the address space. Note
>that the Asus BIOS controls this allocation, and if you read the
>875P datasheet, no where near that amount of address space needs
>to be wasted. I suppose it might depend on whether the Asus BIOS
>makes a fixed allocation for the PCI cards (as opposed to examining
>each card for its requirements) etc. I don't know enough about
>PCI/AGP addressing to be able to say more than that. I mean, there
>are standards for this stuff, and maybe Asus follows what some
>standard says ?
>
>HTH,
> Paul
Then there is this issue which I've come across
"Adding extra memory to your PC can slow it down"
http://firingsquad.com/hardware/building_gaming_opteron_2003_Part2/page14.asp