Windows 7: 4gb RAM installed, sometimes showed 2gb usable

The issue here is people using 32 bit operating systems when they have enough devices that they have run out of address space.

In a computer all bytes in the memory system need a unique name. This is called an address. For example, if you have 2 GB of main memory, then there are 2147483648 bytes of RAM in your machine, each of which require an address for the operating system to communicate to it. To give these all an address you need 31 bits to do it. Now, if/when you have 32 bits, you can name 4 GB (2 bytes to the 32nd power = 4GB).

This is why the total addressable space available in a 32 bit OS is 4GB – the OS runs out of addresses and cannot communicate/locate any more bytes of memory because of that.

You may think ”Hey, 4GB of address space… 4GB of RAM… What’s the problem?”



The problem is that memory isn’t the only thing needing an address. If you install a total of 4GB worth of RAM, the system will detect/use/display less than 4GB of total memory because of address space allocation for other critical functions, such as:

- System BIOS (including motherboard, add-on cards, etc..)
- Motherboards resources
- Memory mapped I/O
- Configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices

Different onboard devices and different add-on cards (devices) will result of different total memory size. e.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.

This limitation applies to most chipsets & Windows XP/Vista 32-bit version operating systems. Again, this is a limitation of the Operating System not having enough address space to allocate to the system *and* the RAM. Not allocating address space to devices renders them inoperable. Not allocating addresses to RAM simply results in the unaddressed section not being used in an otherwise fully functional computer. Therefore the OS designers assign RAM last.


If you install a Windows operating system, and if more than 3GB memory is required for your system, then the below conditions must be met:

1. A memory controller which supports memory swap functionality is used. The latest chipsets like Intel 975X, 955X, Nvidia NF4 SLI Intel Edition, Nvidia NF4 SLI X16, AMD K8 and newer architectures can support the memory swap function.

2. Installation of Windows XP Pro X64 Ed. (64-bit), Windows Vista 64, or other OS which can provide more than 4GB worth of address space.



Note: According to the latest Change Log published by Microsoft, Windows Vista 32bit SP1 will display the installed amount of RAM. This is a display change only.

Thanks for willingness to make a long answer to explain that to me. But my Windows 7 64bit, so was the old Vista (which I upgraded from).

What part of the original post did you not understand? He made it quite clear in his first post that he is having this problem with Windows 7 x64 yet you keep going on and on about the 32 bit limitation that most of us moving to x64 know of already. In fact the 3 GB limitation on 32 bit systems is the main reason most people are moving to x64.

I have the same problem as the thread starter on my Windows 7 x64 and it's frustrating to keep reading people harping on and on about the 32 bit limitation when the questions are clearly to do with 64 bit systems!!

@Dreemuk -
This your first post. Is it your first forum? Please describe your specific problem in a new thread. Don't rant on a professional member, it won't help you fix your PC. It will only cause this and other professionals to pass on helping you.

Scotteq's treatment is an excellent contribution, whether or not it is misplaced.

The solution for the OP's problem has since been discovered and is now a known quick fix.

Dreemuk

Hi and welcome to sevenforums

OK so you have 64 bit and what? traditionally if you have a problem you would want to start a new thread instead of tacking on a 3 month old one. We need a couple of things from you. First we could use your system specs (lower left corner) and is OS clean or upgrade?

Ken

You really need to lose your attitude if you seriously expect anyone to take the time to help you... Atman is right .. highjacking a thread is not looked upon very kindly...

Thanks for the response guys. I stumbled upon this forum in researching this problem and thought instead of starting new thread I should search maybe it has been discussed and answered already.

I'm sorry for the rant. It was just from the sheer frustration of reading so many posts where people have very clearly stated they were having this issue with x64 systems but yet being lectured about the 32 bit limitation again and again.

OK to my problem:

- Acer aspire laptop with an Intel Core 2 Duo 64 bit processor
- 4 GB RAM
- nVidia Geforce graphics 256 MB

I put in a fresh install of Windows 7 Ultimate x64 (formated the HD, clean install) but under System RAM it shows 4.00 GB (3.00 GB usable). System type is 64-bit Operating System. In task manager it shows 3096 GB as total RAM

I have the latest BIOS from the manufacturer Acer but it does not have any option to for "memory remap" that i've read can resolve the problem.

I called the manufacturer Acer and they said the laptop is fully 64 bits compatible i.e all parts of it so were perplexed about the issue too but had no answers.

With my BIOS not supporting memory remapping does that mean I'm stuck with this problem and can't use more that 3 GB of RAM?

Right off the top of my head, I would suspect that you have shared video memory and thats where your problem lies... run GPUZ and post the results, or open a command prompt and enter dxdiag .. save the report and upload it .. we'll go from there

Hey

No sweat abt the rant we all have them. I think I have this one nailed. either in msconfig, or in bios there is a Max Mem setting. It should be uncheck, Max cpu also.

Check it out and let us know

Again welcome

Ken

This is what I get with dxdiag. The graphics card has it's own dedicated memory but can also use shared memory. I heard that should not affect the memory available to OS?

------------------
System Information
------------------
Time of this report: 8/25/2009, 23:08:05
Machine name: Windows 7
Operating System: Windows 7 Ultimate 64-bit (6.1, Build 7600) (7600.win7_rtm.090713-1255)
Language: English (Regional Setting: English)
System Manufacturer: Acer
System Model: Aspire 5630
BIOS: Ver 1.00PARTTBLP
Processor: Intel(R) Core(TM)2 CPU T5500 @ 1.66GHz (2 CPUs), ~1.7GHz
Memory: 4096MB RAM
Available OS Memory: 3070MB RAM
Page File: 1417MB used, 4720MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7600.16385 32bit Unicode
------------
DxDiag Notes
------------
Display Tab 1: No problems found.
Sound Tab 1: No problems found.
Sound Tab 2: No problems found.
Input Tab: No problems found.
--------------------
DirectX Debug Levels
--------------------
Direct3D: 0/4 (retail)
DirectDraw: 0/4 (retail)
DirectInput: 0/5 (retail)
DirectMusic: 0/5 (retail)
DirectPlay: 0/9 (retail)
DirectSound: 0/5 (retail)
DirectShow: 0/6 (retail)
---------------
Display Devices
---------------
Card name: NVIDIA GeForce Go 7300
Manufacturer: NVIDIA
Chip type: GeForce Go 7300
DAC type: Integrated RAMDAC
Device Key: Enum\PCI\VEN_10DE&DEV_01D7&SUBSYS_00901025&REV_A1
Display Memory: 1400 MB
Dedicated Memory: 121 MB
Shared Memory: 1279 MB
Current Mode: 1280 x 800 (32 bit) (60Hz)
Monitor Name: Generic PnP Monitor
Monitor Model: unknown
Monitor Id: LPLCA00
Native Mode: 1280 x 800(p) (59.982Hz)
Output Type: Internal
Driver Name: nvd3dum,nvd3dumx.dll,nvwgf2um, nvwgf2umx.dll
Driver File Version: 7.15.0011.7967 (English)
Driver Version: 7.15.11.7967
DDI Version: 9Ex
Driver Model: WDDM 1.0
Driver Attributes: Final Retail
Driver Date/Size: 3/6/2009 11:52:00, 5976064 bytes
WHQL Logo'd: Yes
WHQL Date Stamp:
Device Identifier: {D7B71E3E-4297-11CF-8A6C-9B2001C2CA35}
Vendor ID: 0x10DE
Device ID: 0x01D7
SubSys ID: 0x00901025
Revision ID: 0x00A1
Driver Strong Name: oem12.inf:NVIDIA.Mfg.NTamd64.6.0:nv_G7x:7.15.11.7967ci\ven_10de&dev_01d7&subsys_00901025
Rank Of Driver: 00F60001