P5LD2 Deluxe appropriates 896 MB RAM

[Michael]

Hi folks,

we recently bought a workstation with an Asus P5LD2 Deluxe MB, a
Pentium D 830 CPU (3.0 GHz) and 4GB RAM (Kingston, 400MHz DDR II
PC2-3200-CL3).

Unfortunately, the BIOS decides to 'appropriate' 896MB, so only 3200MB
are available for use. I was able to reduce the appropriated memory to
640MB after replacing the PCI Express graphics card (Saphire Radeon X600)
with an old PCI card.

However - I was wondering why my BIOS appropriates this large amount of
RAM.

The detailed message from BIOS System Information is:

BIOS: V0312
Build Date: 06/14/05
Processor: Intel Pentium D CPU 3.00 GHz
Speed: 3000 MHz
Count: 2

System Memory

Total: 4096 MB
Appropriated: 896 MB
Available: 3200 MB


Any suggestions...I want my memory back!

Michael

 

[Paul]

Hi folks,

we recently bought a workstation with an Asus P5LD2 Deluxe MB, a
Pentium D 830 CPU (3.0 GHz) and 4GB RAM (Kingston, 400MHz DDR II
PC2-3200-CL3).

Unfortunately, the BIOS decides to 'appropriate' 896MB, so only 3200MB
are available for use. I was able to reduce the appropriated memory to
640MB after replacing the PCI Express graphics card (Saphire Radeon X600)
with an old PCI card.

However - I was wondering why my BIOS appropriates this large amount of
RAM.

The detailed message from BIOS System Information is:

BIOS: V0312
Build Date: 06/14/05
Processor: Intel Pentium D CPU 3.00 GHz
Speed: 3000 MHz
Count: 2

System Memory

Total: 4096 MB
Appropriated: 896 MB
Available: 3200 MB


Any suggestions...I want my memory back!

Michael

The Silicon Image 3132 is PCI Express based. The Marvell
88E8053 is PCI Express based. Perhaps if they were both
disabled, and then an ordinary PCI Ethernet card was used,
you would get some memory back.

To understand the consumption, get a copy of the 945P datasheet
and the ICH7(R) datasheet. The chips are connected together by
the 1GB/sec DMI bus. The 945P datasheet has some information
on how the TOLUD (top of low usable DRAM) is calculated. There
are several diagrams, such as "PCI Memory Address Range"
on page 218 of 30750201.pdf.

(Download the two documents in the Datasheet section.)
http://developer.intel.com/design/chipsets/945p/documentation945p.htm

I would think disabling all PCI Express devices might buy you
a small improvement, but after that, you are likely out of
options (unless you know a way to completely reprogram the
decodes set up by the BIOS, before the OS attempts to load).

Perhaps the worst boards for the problem you are seeing, are
the SLI boards. They punch a big hole in the address space.

In terms of debugging utilities, find a tool that knows how
to dump the Northbridge registers. That will allow you to
observe how the address spaces are defined. I think CPUZ might
have a dump option (presumably to aid the developer in bug
hunting and fixes). Everest from Lavalys.com might be another
utility you could try out. For pure raw data dumping, another
option might be WPCREDIT. I believe I've looked at a Northbridge
on one of my boards with this tool:

http://hp.vector.co.jp/authors/VA002374/img/soft/wpcredit.jpg
http://hp.vector.co.jp/authors/VA002374/src/download.html

Good luck,
Paul

 

[Robert Hancock]

Hi folks,

we recently bought a workstation with an Asus P5LD2 Deluxe MB, a
Pentium D 830 CPU (3.0 GHz) and 4GB RAM (Kingston, 400MHz DDR II
PC2-3200-CL3).

Unfortunately, the BIOS decides to 'appropriate' 896MB, so only 3200MB
are available for use. I was able to reduce the appropriated memory to
640MB after replacing the PCI Express graphics card (Saphire Radeon X600)
with an old PCI card.

However - I was wondering why my BIOS appropriates this large amount of
RAM.

The detailed message from BIOS System Information is:

BIOS: V0312
Build Date: 06/14/05
Processor: Intel Pentium D CPU 3.00 GHz
Speed: 3000 MHz
Count: 2

System Memory

Total: 4096 MB
Appropriated: 896 MB
Available: 3200 MB


Any suggestions...I want my memory back!

It's not the BIOS appropriating the memory, really.. it's the chipset
and video card using up some of the address space for memory-mapped I/O.

Many Athlon 64 boards have an option to remap the memory "covered up" by
MMIO space to above 4GB, however that requires that the OS support using
PAE memory above 4GB in order to work. (Not sure if normal XP does or
not..) I'm not sure if any Intel boards have anything like this, either..

 

[Michael]

To understand the consumption, get a copy of the 945P datasheet
and the ICH7(R) datasheet. The chips are connected together by
the 1GB/sec DMI bus. The 945P datasheet has some information
on how the TOLUD (top of low usable DRAM) is calculated. There
are several diagrams, such as "PCI Memory Address Range"
on page 218 of 30750201.pdf.

(Download the two documents in the Datasheet section.)
http://developer.intel.com/design/chipsets/945p/documentation945p.htm

I would think disabling all PCI Express devices might buy you
a small improvement, but after that, you are likely out of
options (unless you know a way to completely reprogram the
decodes set up by the BIOS, before the OS attempts to load).

Hi,

thanks for the detailed information!

The 945P does not seem to be our chipset of choice in the future.

Do you know if the 955 has similar problems?

Michael

 

[Paul]

Hi,

thanks for the detailed information!

The 945P does not seem to be our chipset of choice in the future.

Do you know if the 955 has similar problems?

Michael

The 955 must have remapping, because it has 8GB max
RAM capability. But, as Robert explained, you may need
something like PAE to get at the memory.

Get the 955X MCH datasheet here. Section 7.4.1 on page 181
mentions remapping, as do other sections of the document.

http://developer.intel.com/design/chipsets/955X/documentation955x.htm

Getting to use the memory in systems like this requires OS support,
application support, hardware support, BIOS support etc. It will
be a struggle to actually get to use your memory, whether you use
all server grade stuff or not.

In terms of remapping support, 955X remaps, the Atnlon 64 bit
processors have remapping too, as do a whole bunch of server boards
from the likes of Tyan, Supermicro, even Asus server motherboards.
On some Athlon64 motherboards, the remapping BIOS option was not
available on the first BIOS release, so you need a certain minimum
level to get support.

Another minor issue, is IOMMU. The Athlon64 has some kind of
remapping for PCI, so that 32 bit PCI cards can live in a
64 bit environment. With Intel, it may take "bounce buffers",
but if your application doesn't do primarily I/O, chances
are you won't care.

Trying to get more than 3GB of memory will be an education
for you. So far, I don't think anybody I've discussed this
with, has ever come back to post a success story (they're
probably too busy).

Try searching for PAE on this site - the search button is at
the top of the page:

http://forums.2cpu.com/showthread.php?threadid=53859&highlight=pae

Paul