A8N-SLI with 4 GB RAM

[JP]

Hi,

I fit this motherboard with 4 stick of 1 GB DDR 400,

In the bios, the 4096 MB are recognized
unfortunatly in the bios and in windows, it only see 2.25 GB or extended
memory (usable memory)
thats with 2 PCI express board,

If I remove one, then the memory goes to 2.75 GB

I know this is usualy a chipset limitation that reserve some memory, but on
normal board it would make 3.5-3.8 GB available.

I cannot mange to go higher than 2.25 GB, that, this seems to be related to
the chipset or board, since on an other computer 3.5 GB are detected.
On AGP board a way to increse the usable memory is to change the AGP
aperture size, but here with PCI express there is no option for that :/

If someone has idea ???

 

[Paul]

Hi,

I fit this motherboard with 4 stick of 1 GB DDR 400,

In the bios, the 4096 MB are recognized
unfortunatly in the bios and in windows, it only see 2.25 GB or extended
memory (usable memory)
thats with 2 PCI express board,

If I remove one, then the memory goes to 2.75 GB

I know this is usualy a chipset limitation that reserve some memory, but on
normal board it would make 3.5-3.8 GB available.

I cannot mange to go higher than 2.25 GB, that, this seems to be related to
the chipset or board, since on an other computer 3.5 GB are detected.
On AGP board a way to increse the usable memory is to change the AGP
aperture size, but here with PCI express there is no option for that :/

If someone has idea ???

The normal way to resolve this issue, would be to find the datasheet
for the Northbridge and see how the memory map works. Unfortunately,
Nvidia doesn't make datasheets available to the public, so this is
out of the question.

There is a comment on PCI Express in the Intel 925X datasheet pg.167
ftp://download.intel.com/design/chipsets/datashts/30146402.pdf

"Unlike AGP4x, PCI Express has no concept of aperture for PCI
Express devices. As a result, there is no need to translate
addresses from PCI Express."

Perhaps the PCI Express video cards are simply memory mapped ?

I don't have access to any PCI Express standards, so the
answer to the question may be hidden in one of those specifications.

It seems strange that removing a PCI Express video card is
freeing up 512MB of space. If the new PCI Express video cards
are being memory mapped, and the video card had 256MB of memory,
you would think the BIOS would only reserve 256MB of memory.
Section 9.3.6 in the Intel 925X document, states that two
address ranges are decoded, and one supports WC attribute
for write combining (Uncached Speculative Write Combining).

But, this Linux kernel discussion says:

http://www.kerneltraffic.org/kernel-traffic/kt20040614_263.txt

"PCI Express does not have a centralized aperture like agp
that can be marked WC. Instead, individual system pages of
memory need to be marked WC via PAT in the page tables."

so maybe Asus is allocating too much space for the video
cards ?

Perhaps you could contact Asus tech support, and report your
findings. Maybe in a future BIOS, they can make more of your
system memory available.

There is little free information to go on, concerning such
things.

For example, this is the only picture I've been able to find,
of the PCI Express packet format:

http://www.esemagazine.co.uk/common/viewer/archive/2004/Jul/26/feature3.phtm
(PCI Express packet format)
http://www.esemagazine.co.uk/archive/2004/Jul/26/valid_fig1.gif

Maybe you could unplug both PCI-Express video cards, and use
a PCI video card instead ))

http://www.newegg.com/app/ViewProdu...rice=&maxprice=&mfrcode=0&DEPA=0&InnerCata=48

Paul

 

[Roland Scheidegger]

Hi,

I fit this motherboard with 4 stick of 1 GB DDR 400,

In the bios, the 4096 MB are recognized
unfortunatly in the bios and in windows, it only see 2.25 GB or extended
memory (usable memory)
thats with 2 PCI express board,

If I remove one, then the memory goes to 2.75 GB

I know this is usualy a chipset limitation that reserve some memory, but on
normal board it would make 3.5-3.8 GB available.

I cannot mange to go higher than 2.25 GB, that, this seems to be related to
the chipset or board, since on an other computer 3.5 GB are detected.
On AGP board a way to increse the usable memory is to change the AGP
aperture size, but here with PCI express there is no option for that :/

If someone has idea ???

I believe the bios of this board fully supports 4GB ram. You'd need a
PAE-aware OS, however. Windows XP won't cut it, neither home nor
professional.
Windows 2000 and 2003 Server Editions will do (not the standard editions
afaik, only Enterprise and Datacenter, which might be a bit on the
expensive side...).
Linux (probably all at least somewhat recent distributions) should
support it too.
If you're feeling adventorous, you could try the preview of windows xp
pro x64 edition (free download), which fully supports that too.

Roland

 

[Roland Scheidegger]

I believe the bios of this board fully supports 4GB ram. You'd need a
PAE-aware OS, however. Windows XP won't cut it, neither home nor
professional.
Windows 2000 and 2003 Server Editions will do (not the standard editions
afaik, only Enterprise and Datacenter, which might be a bit on the
expensive side...).
Linux (probably all at least somewhat recent distributions) should
support it too.
If you're feeling adventorous, you could try the preview of windows xp
pro x64 edition (free download), which fully supports that too.

Some addendum, it's actually not really true that windows XP doesn't
support PAE. It kinda does, you can enable that with the /PAE switch in
your boot.ini. It still won't make all ram available, however.

http://www.jsiinc.com/SUBR/tip8700/rh8744.htm
http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/sp2mempr.mspx

Roland

 

[Robert Hancock]

Hi,

I fit this motherboard with 4 stick of 1 GB DDR 400,

In the bios, the 4096 MB are recognized
unfortunatly in the bios and in windows, it only see 2.25 GB or extended
memory (usable memory)
thats with 2 PCI express board,

If I remove one, then the memory goes to 2.75 GB

I know this is usualy a chipset limitation that reserve some memory, but on
normal board it would make 3.5-3.8 GB available.

I cannot mange to go higher than 2.25 GB, that, this seems to be related to
the chipset or board, since on an other computer 3.5 GB are detected.
On AGP board a way to increse the usable memory is to change the AGP
aperture size, but here with PCI express there is no option for that :/

If someone has idea ???

You need to enable PAE in Windows, otherwise you won't be able to see it
all.

 

[news.skynet.be]

Some addendum, it's actually not really true that windows XP doesn't
support PAE. It kinda does, you can enable that with the /PAE switch in
your boot.ini. It still won't make all ram available, however.

http://www.jsiinc.com/SUBR/tip8700/rh8744.htm
http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/sp2mempr.mspx

Roland

I'm sure this problem is not about PAE but more related to the nfoce 4 or
the board/bios

I tried with windows XP 64 bit and the problem is the same, it would even be
the same with Linux.

I made few more test and I found out that although in the bios it correctly
reports 4096 Mo or RAM, on the screen before it boots to the hard disk, it
reports only 2.7 Gb or extended memory.

in addition I didnt had to modify anything to get 3.5 Gb on WIndows XP 32
bit on the other computer.

a second test was to put 2x1 Gb + 2X512 mb, and still the system find the
2.75 Gb

I guess asus reserve away too much space for the chipset/graphic boards etc

 

[Roger Hamlett]

I'm sure this problem is not about PAE but more related to the nfoce 4
or the board/bios

I tried with windows XP 64 bit and the problem is the same, it would
even be the same with Linux.

I made few more test and I found out that although in the bios it
correctly reports 4096 Mo or RAM, on the screen before it boots to the
hard disk, it reports only 2.7 Gb or extended memory.

in addition I didnt had to modify anything to get 3.5 Gb on WIndows XP
32 bit on the other computer.

Worth being aware here, that the problem is not with 'supporting' 3.5GB of
RAM, but 'using' it. WXP, by default, only allocates 2GB to the 'user
space', and retains the rest for the 'system'. This is modifyable using
the /3GB switch in boot.ini, which allows up to 3GB to be allocated to the
user space. Your system with 3.5GB detected, probably performed no better
than a system with about 2.5GB of RAM, with perhaps 1GB, hardly being
used.

a second test was to put 2x1 Gb + 2X512 mb, and still the system find
the 2.75 Gb

I guess asus reserve away too much space for the chipset/graphic boards
etc

Yes.

Best Wishes

 

[Roland Scheidegger]

I'm sure this problem is not about PAE but more related to the nfoce
4 or the board/bios

Well, if the bios and OS would fully support PAE (or instead of this
hack, x86_64), you would get the FULL
4GB. And I think I've read the board can do it - well maybe I'm
remembering that wrong. I've skimmed through the manual and there is
indeed nothing indicating it could do it. That's disappointing to say
the least :-(.

I tried with windows XP 64 bit and the problem is the same, it would
even be the same with Linux.

I made few more test and I found out that although in the bios it
correctly reports 4096 Mo or RAM, on the screen before it boots to
the hard disk, it reports only 2.7 Gb or extended memory.

I believe other boards behave the same, in the bios they will show you
the amount you've actually installed, but when booting they will show
the amount which is mapped.

I guess asus reserve away too much space for the chipset/graphic
boards etc

This may be true. Unless there is something about PCI-Express which
really requires to reserve such large amounts.
Did you try a bios update?

Roland

 

[out_of_it_all]

I'm sure this problem is not about PAE but more related to the nfoce 4 or
the board/bios

I tried with windows XP 64 bit and the problem is the same, it would even be
the same with Linux.

I made few more test and I found out that although in the bios it correctly
reports 4096 Mo or RAM, on the screen before it boots to the hard disk, it
reports only 2.7 Gb or extended memory.

in addition I didnt had to modify anything to get 3.5 Gb on WIndows XP 32
bit on the other computer.

a second test was to put 2x1 Gb + 2X512 mb, and still the system find the
2.75 Gb

I guess asus reserve away too much space for the chipset/graphic boards etc

same problem here. built system specifically for xp 64. but install any more
than 2 gigs and will fail bios mem test (turn off quik boot and full screen
logo) every time. hits the 2 gig mark and reboots continuously. escape test and
get the 2.75. xp 32 shows 2 gig. xp 64 shows 2.75. bios shows 4. 3dmark shows 1
gig in all 4 slots. tried every bios up to 1003_007 anyway. haven't seen 010
or 1004 yet. tried 4 gigs kingston, 4 gigs patriot, 3 gigs patriot, and mixed
in 1 gig corsair in various slots. all pc 3200 unbuffered. reading on corsair
site they say anytime you go over 2 gigs to used registered mem. anybody know
if it's compatible? moot point for me anyway as i've already spent all i can.
went with 939 instead of 940 to get away from registered dimms (and better
selection of motherboards)