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My notebook is Satellite A100, which supports RAM expandability is 4GB maximum. However, my notebook is already plugged by 2 x 2GB RAM (that is, having 4GB right now).

So it means, either windows 7 32-bit or 64-bit will recognize only 3GB usable. It's so sad!

Could you please suggest me whether I should install 32-bit or 64-bit? Also, is there anyway to improve maximum RAM recognize by Windows 7 in my case? (something like reaching 4GB usable in 64-bit on current chipset that supports RAM expandability only in 4GB maximum...)

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If you current have 4GB installed then Windows 7 x64-bit would see 4GB of memory and could use that amount. This assumes your CPU has x64-bit arch support. – Ramhound Oct 6 '11 at 18:05

If your processor supports 64 bit system and you have 4GB of RAM then usually you would go with 64bit system. However if this is your correct processor you will be unable to use 64 bit.

*Note - This is the one that seemed to come stock with that specific laptop

Intel CPU specs

In 32 bit you may see 3GB but in 64 you should be seeing all 4GB.

Extra Info: If you are only seeing 3GB of RAM and the system is completely stock then you may have issues with the actual sticks. This link shows a few ways you can check for bad RAM.

Examples: Check Computer properties vs. Bios, use software, etc.

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That system likely has an Intel 900 mobile series chipset (910M/915M/945M/965M) and is only capable of addressing 32-bits worth of RAM, meaning that with 4 GB installed, some is always lost because the chipset is unable to remap the physical RAM to addresses > 4 GB. – afrazier Oct 6 '11 at 18:30
In the past, I have the same situation, 4Gb of RAM installed but Win7 64Bit only recognized 3Gb, the solution in my case was upgrading the BIOS and after that, all 4Gb of RAM are recognized in Win7 64Bit – jhcaiced Oct 6 '11 at 18:54

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