P5GDC and 4 GB RAM...

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fred

Hi all,

I have a P5GCD mobo on which I want to install 4 modules of 1 GB each.

I tried 2 * Corsair Twinx PC3200 2 GB but it fails : only 3.2 GB are
recognized.

Does anyone tempt to install 4 modules of 1 GB on a such mobo ?

What kind of model & vendor could you advise ?


Thanks in advance.
 
fred said:
Hi all,

I have a P5GCD mobo on which I want to install 4 modules of 1 GB each.
Click to expand...
I forgot to mention : all 4 modules are ok. On a P4P800, they work fine
(4 GB ok)

Corsair website mention that many modules work with this mobo.
But do they work with 4 GB ?

Regards,
 
I have read here, from other knowledgable readers, that Asus motherboards
can only access up to 3.2 GB of RAM, regardless of RAM configuration. I'm
not sure why???
 
I forgot to mention : all 4 modules are ok. On a P4P800, they work fine
(4 GB ok)

Corsair website mention that many modules work with this mobo.
But do they work with 4 GB ?

Regards,
Click to expand...

The problem is one of address space. Some address decodes are
needed for PCI, PCI Express, AGP, any system busses, up in the high
address space. For a non-server chipset, they punch a hole in
the DRAM decoded address space, to make room for those other
address spaces. As DaveW points out, it means you buy 4GB of
memory, but only get to use 3.2GB or so. The other 0.8GB cannot
be used, because it cannot be addressed.

You could also consider buying 2x1GB + 2x512MB for a total of 3GB,
and you would get to use all of it. If you are a rich guy, having
four identical sticks offers the possibility for interleaved
memory access patterns, and maybe a couple percent more
memory bandwidth, but that would not be good bang for the
buck.

If I needed more than 2GB of memory, I think my personal
choice would be the 4x1GB configuration, because I like to
fill the machine with my final memory config from day one.

In terms of the size of the addressing hole needed for the
system busses, if you minimize the number of busses
being used, then more address space is made available.
If you only had a PCI video card, and no PCI Express or
AGP cards on a motherboard, then perhaps 3.5GB of system
memory would be usable. The SLI motherboards are particularly
hard hit by this issue, and the usable memory drops below
3GB in some cases, when two video cards are present.

For more info, see page 205 for an example of a memory map:
ftp://download.intel.com/design/chipsets/datashts/30146703.pdf

Paul
 
DaveW said:
I have read here, from other knowledgable readers, that Asus motherboards
can only access up to 3.2 GB of RAM, regardless of RAM configuration. I'm
not sure why???
Click to expand...

Can't be that knowledgeable if that's what they said.. However, most
(all?) chipsets for Intel CPUs (other than server or workstation
chipsets) do not support moving RAM above the 4GB boundary to get it out
of the way of the PCI or PCI Express memory-mapped IO regions. Therefore
some of that memory is covered up and unusable. It has nothing to do
with the type of modules being used.

Most Athlon 64 boards support this since the remapping is handled by the
CPU's memory controller itself.

However, even if you do have memory remapping support, you either need a
64-bit OS or one that supports accessing memory with PAE above 4GB.
Normal WinXP Home/Pro does NOT, you need a server version of Windows or
64-bit Edition.
 
(e-mail address removed) (Paul) a écrit :
The problem is one of address space. Some address decodes are
needed for PCI, PCI Express, AGP, any system busses, up in the high
address space. For a non-server chipset, they punch a hole in
the DRAM decoded address space, to make room for those other
address spaces. As DaveW points out, it means you buy 4GB of
memory, but only get to use 3.2GB or so. The other 0.8GB cannot
be used, because it cannot be addressed.

You could also consider buying 2x1GB + 2x512MB for a total of 3GB,
Click to expand...
3 x 1 GB works fine.
and you would get to use all of it. If you are a rich guy, having
four identical sticks offers the possibility for interleaved
memory access patterns, and maybe a couple percent more
memory bandwidth, but that would not be good bang for the
buck.

If I needed more than 2GB of memory, I think my personal
choice would be the 4x1GB configuration, because I like to
fill the machine with my final memory config from day one.
Click to expand...
Me too. This is my config.
In terms of the size of the addressing hole needed for the
system busses, if you minimize the number of busses
being used, then more address space is made available.
If you only had a PCI video card, and no PCI Express or
AGP cards on a motherboard, then perhaps 3.5GB of system
Click to expand...
I have a PCI Express card. An Asus.
memory would be usable. The SLI motherboards are particularly
hard hit by this issue, and the usable memory drops below
3GB in some cases, when two video cards are present.

For more info, see page 205 for an example of a memory map:
ftp://download.intel.com/design/chipsets/datashts/30146703.pdf
Click to expand...
broken.

So, if I understand, I can not have 4 GB on ia32 Asus mobo.
Neither with another mobo vendor nor another DDR RAM vendor.
:-(

So, what think of that Asus claims that one can use 4 GB ???
:-(((

Thanks.
 
fred <[email protected]> a écrit :

On FAQ Asus website, one can read :

This limitation applies to most chipsets & Windows XP 32-bit version operating system.

If you install Windows XP 32-bit version operating system, we
recommend that you install less than 3GB of total memory. If more than
3GB memory is required for your system, then below two conditions must
be met:

1. The memory controller which supports memory swap functionality is
used. The latest chipsets like Intel 955X, Nvidia NF4 SLI Intel
Edition, Nvidia NF4 SLI X16, and AMD K8 CPU architecture can support
the memory swap function.

2. Windows XP Pro X64 Ed. (64-bit) or other OS which can address more than 4GB memory.

BIOS only see 3.2 GB. I don't understand how my OS can see more than
3.2 GB, knowing that I (only) have a linux box, which can address more
than 2 GB (up to 64) ???
 
fred said:
fred <[email protected]> a écrit :

On FAQ Asus website, one can read :
Click to expand...
From Intel & Asus website, it seems that a P5WD2 Premium should work
fine because it's a i955x chip and mobo can accept up to 8 GB.

Did everyone test this config : 4 * 1 GB on a P5WD2 ?

Thnks.
 
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