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RAM installed = 4096MB, RAM available = 3550MB

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August 8, 2011 3:41:13 PM

Hello everybody!

I've just installed four 1GB memory modules on my Asus P5LD2 motherboard
but the BIOS says: RAM installed = 4096 MB, RAM available = 3550 MB.

After reading a couple of forum posts (about other motherboards) that suggested
changing a "memory hole remappping" BIOS setting I've looked for it but there is
no such thing in mine.

How do I make all the installed RAM available to the OS?

Does upgrading the BIOS solve the problem?
How risky is that? I've never done that before.

Thanks for your help!
a c 207 Ĉ ASUS
a c 347 } Memory
a c 716 V Motherboard
August 8, 2011 3:51:41 PM

Welcome to Tom's Forums! :) 

IF you have a 32-bit OS then 3.0GB~3.50GB is normal this is due to reserved addressing to accommodate Virtual Memory and turning-off VM won't correct the problem. Further, IF a MOBO has an onboard GPU 0.25GB~0.50GB goes to 'shared memory' via the BIOS, but in looking there's no onboard GPU/VGA out -> http://usa.asus.com/Motherboards/Intel_Socket_775/P5LD2...
August 8, 2011 10:15:41 PM

Hi jaquith! Thanks for your reply!


> IF you have a 32-bit OS then 3.0GB~3.50GB is normal this is due to reserved addressing
> to accommodate Virtual Memory and turning-off VM won't correct the problem.

I'm aware of that. I was running a 64-bit OS: SystemRescueCD w/ the x86_64 kernel.
In fact just to be sure I've run another distro: the 64-bit version of StressLinux (in this
case the 32-bit and the 64-bit version are available in two distinct CDs, so no mixup
is possible).


> Further, IF a MOBO has an onboard GPU 0.25GB~0.50GB goes to 'shared memory' via the BIOS,
> but in looking there's no onboard GPU/VGA out -> http://usa.asus.com/Motherboards/Intel_Socket_775
> /P5LD2/#specifications

No there is no onboard GPU.

Anyway I first tested only one pair of 1GB RAM modules, then removed it and tested
the second pair (using memtest86+ v2.40). During the tests memtest86+ resported
RAM installed = RAM available = 2048 MB.


I've already looked into the available BIOS settings but didn't find any memory-mapping
option.

Do you think a BIOS upgrade is likely to solve the problem?
And how safe is it? As I said I've never done that so I really don't know.

I'd rather live with only 3550MB than risk ending with a useless motherboard in my hands.

Thanks for your help!
Related resources
August 8, 2011 10:56:21 PM


Just to make clear it seems to be a BIOS issue (not an OS-related one) here is
what I see on my "BIOS -- Main -- System Information" screen:

AMIBIOS Version:
Build Date:

Processor Type:
Speed:
Count:

System Memory Total: 4096 MB
Appropriated: 640 MB
Available: 3456 MB
a c 207 Ĉ ASUS
a c 347 } Memory
a c 716 V Motherboard
August 8, 2011 11:20:52 PM

The {Appropriated: 640 MB} is reserved by the BIOS for 'something', 40~50MB is vanilla typical HW Reserved for any OS which leaves 500MB+ unaccounted for, and there's no way it's a bad stick - so the BIOS is reserving it for 'something' connected and 'something' probably PCIe eg 'Shared' OS RAM for the GPU.

My assumption, is 'RAM available = 3550MB' in SystemRescueCD is the same as 'Available' to Windows 'Available' which is Installed - BIOS H/W Reserved - In Use {or Standby {Shared} + Free} depending how you look at it. H/W Reserved = Installed - Total; in that case Total is ALL that concerns me.

Bottom-Line, it's not a BIOS/RAM/MOBO issue.

http://i1013.photobucket.com/albums/af254/Jaquith/RM_7P...

See 'Shared'
http://i1013.photobucket.com/albums/af254/Jaquith/WEI_H...
August 8, 2011 11:53:16 PM

The Intel 945 chipset only has a 32bit host interface. This gives the same limitation as running 32bit desktop Windows. So your hardware cannot make use of it all.
a c 207 Ĉ ASUS
a c 347 } Memory
a c 716 V Motherboard
August 9, 2011 1:15:15 AM

^ @mikrev007 - Absolutely right! Very Good!!!

Intel 945P
Intel ICH7R
Front Side Bus 1066/800/533 MHz
Memory 4 x DIMM, max. 4GB, DDR2 667/533/400, Non-ECC, un-buffered memory
Dual Channel Architecture
* Due to general PC architecture, a small amount of memory is reserved for system usage and thus the actual memory size is less than the stated amount.
!