4GB RAM seen only as 3.5GB - any chance to fix?

Message boards : Number crunching : 4GB RAM seen only as 3.5GB - any chance to fix?
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Profile Raistmer
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Message 1671904 - Posted: 30 Apr 2015, 8:33:36 UTC
Last modified: 30 Apr 2015, 8:35:02 UTC

Recently I had opportunity to increase memory amount on old Athlon 64 Venice host from 2GB to 4GB.
But both BIOS and Windows 2003 x64 server report only 3,5GB installed.
While tools like CPU-Z see 4 DIMMs each 1024MB.

What is going on and is there any chance to get access to whole 4GB of RAM ?

OS is x64 so it's strange a little to get such memory cut.
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Message 1671923 - Posted: 30 Apr 2015, 9:30:26 UTC - in response to Message 1671904.  

Other than some odd BIOS issue (Check motherboard manufacturer's web site for BOIS updates, see if there are any relating to memory detection/support issues?) I'd suggest running the system with only 1 DIMM installed, and see how much memory is reported by the BIOS and the OS.
Remove that module, insert another. Repeat until all have been done, to check to see if one of the modules is at fault.

I did once have limited available memory on a system due to an addon card taking up memory address space, but that was on much, much older hardware.
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Message 1671930 - Posted: 30 Apr 2015, 9:50:45 UTC - in response to Message 1671904.  

What is the motherboard make and model? Very likely it is a BIOS issue. Many original Athlon boards, such as those for your Venice chip, didn't fully support 4GB of RAM. Though sometimes it was as simple as changing a memory option too.
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Message 1671955 - Posted: 30 Apr 2015, 11:17:06 UTC
Last modified: 30 Apr 2015, 11:18:12 UTC

Already tried to change slots and change memory modules.
Up to 3 GB it sees ok, from 4-th only ~1/2 is visible.
Hence it's not some faulty stick, it's limitation on total installed memory.

Motherboard is Gigabyte GA-K8NSC-939

Manual says 4GB supported...
http://www.gigabyte.ru/products/page/mb/ga-k8nsc-939/specs/
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Message 1671957 - Posted: 30 Apr 2015, 11:23:23 UTC

On my Windows 8.1 HP PC i have 20 GB installed, but 827 MB are hardware reserved. I am running 4 Atlas@home tasks on its A10 6700 AMD CPU.
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Message 1672006 - Posted: 30 Apr 2015, 13:16:45 UTC

In BIOS: is Memory Remap Enable?
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Message 1672041 - Posted: 30 Apr 2015, 14:55:50 UTC

Here is some of the small print from the web site:

* Due to standard PC architecture, a certain amount of memory is reserved for system usage and therefore the actual memory size is less than the stated amount.

You are probably stuck with only 3.5G of useable memory.

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Message 1672100 - Posted: 30 Apr 2015, 16:41:07 UTC - in response to Message 1672006.  
Last modified: 30 Apr 2015, 16:42:52 UTC

In BIOS: is Memory Remap Enable?

Did not able to find such option there.
Single mention that resembles is: USB memory type
with options SHADOW/Base memory (640k).
But switching between them did not change memory amount found by BIOS.
All other memory options about DRAM timings, frequencies (it's 333MHz BTW) and various delays (all in auto currently, cause I reset all OCing it had before).

RE all kinds of memory reservation: would be good to understand why this reservation happens with 4GB installed and did not with 2GB or 3GB installed? Other hardware not needed memory then?...
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Message 1672141 - Posted: 30 Apr 2015, 17:34:28 UTC

Did not able to find such option there.


In the BIOS press Ctrl + F1 and check that option Memory Remap appears.
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Message 1672183 - Posted: 30 Apr 2015, 18:54:38 UTC - in response to Message 1672141.  

Did not able to find such option there.


In the BIOS press Ctrl + F1 and check that option Memory Remap appears.


Wow, thanks a lot!!!
Finally I found it inside Advanced Chipset Options menu (that appeared when I used Ctrl-F1 as you suggested)
Now BIOS sees whole 4GB. And OS sees those 4GB too.
Thanks again!
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Message 1672506 - Posted: 1 May 2015, 8:09:43 UTC - in response to Message 1672183.  

For those that are interested, I did a bit of searching to find out just what the Memory Mapping option is.
After not finding much of use, I stumbled across this article in Wikipedia.

Why Memory Mapping is necessary in some BIOSes.


Very roughly, PCI devices using memory-mapped I/O use the same address space for both physical memory and to communicate with hardware devices.
As 32-bit hardware has a total of four gigabytes of addressable memory, some of the real physical memory of a 32-bit machine, when enough memory is installed, needs to be sacrificed by making it hidden so the devices have room to communicate.

When running a 64bit OS, the 32bit address limitation (obviously) no longer applies, and the usual fix is to remap some of the 2-4GB address spaces to above 4GB.

Unfortunately not having Memory Remapping enabled by default affects 64bit operating systems as the way this is accomplished is with the BIOS & depends on the type of chipset in use, and having it enabled by default will lead to major problems if running a 32bit OS.
Activating this for traditional 32-bit operating systems does more harm than good, as the remapped memory (often larger than the PCI hole itself) is unusable to such operating systems, even though e.g. Windows Vista will show such memory to physically exist on the "System Properties" page.

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Message 1672520 - Posted: 1 May 2015, 10:17:47 UTC - in response to Message 1672183.  

Raistmer, I'm glad I could help You.
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Message 1672529 - Posted: 1 May 2015, 11:06:01 UTC - in response to Message 1672506.  

For those that are interested, I did a bit of searching to find out just what the Memory Mapping option is.
After not finding much of use, I stumbled across this article in Wikipedia.

Why Memory Mapping is necessary in some BIOSes.


Very roughly, PCI devices using memory-mapped I/O use the same address space for both physical memory and to communicate with hardware devices.
As 32-bit hardware has a total of four gigabytes of addressable memory, some of the real physical memory of a 32-bit machine, when enough memory is installed, needs to be sacrificed by making it hidden so the devices have room to communicate.

When running a 64bit OS, the 32bit address limitation (obviously) no longer applies, and the usual fix is to remap some of the 2-4GB address spaces to above 4GB.

Unfortunately not having Memory Remapping enabled by default affects 64bit operating systems as the way this is accomplished is with the BIOS & depends on the type of chipset in use, and having it enabled by default will lead to major problems if running a 32bit OS.
Activating this for traditional 32-bit operating systems does more harm than good, as the remapped memory (often larger than the PCI hole itself) is unusable to such operating systems, even though e.g. Windows Vista will show such memory to physically exist on the "System Properties" page.


Thanks for info, interesting that BIOS microcode does that part of job still, even with all those Windows OS Plug&Play abilities to remap IRQs and I/O ranges.
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Message 1672530 - Posted: 1 May 2015, 11:09:38 UTC - in response to Message 1672520.  

Raistmer, I'm glad I could help You.

I already passed that info to friend that experienced same issue with own old PC so you helped him too.
There are some other interesting items in that hidden menu, thank you!
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Message 1674923 - Posted: 7 May 2015, 23:21:00 UTC - in response to Message 1672530.  

I had the same problem with an ASUS A8Nsli Deluxe socket 939 board. I updated the BIOS from a 2004 date to their latest which was Oct. of 2006. Even though it was still old, it solved my problem.
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Message boards : Number crunching : 4GB RAM seen only as 3.5GB - any chance to fix?


 
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