Why won’t Windows detect my full 4GB worth of RAM?


Most people know that adding RAM to an ailing computer can provide an immediate improvement in performance; however, did you know that Windows doesn’t always detect the full amount?

Let’s say your laptop is feeling morose – it’s slow, it’s indolent and generally very unwilling to execute your requests with the same alacrity it had when you first brought it.

So you Google around and get the notion to buy more RAM.

You decide that 4GB is a reasonable amount.  So after shopping around for the best deals, you place the order, receive the package, install the RAM but… you’re aghast when you discover that only 2.97GB of the full 4GB is usable!

What gives?

  • Is the RAM bad?
  • Did you install it wrong?
  • Do you need to update Windows?

The answer to each question is no, no and no.

You’re probably running the 32bit version of Windows, you should check to verify, because the 32bit version (also known as x86) can only understand 3GB of RAM – tops.  In fact, the 32bit version of Windows will NEVER let you use the full amount you paid for and the reason for this boils down to one word:


Computers work in binary.  Stuff is either on or off.

Since there are a maximum of two states, computers love using base 2 for calculations.  Humans use base 10 because it’s convenient (10 fingers, 10 toes) but computers live in a world of true or false.

So if you multiply base 2 by itself 32 times you’ll get 2 to the 32nd power which is 4,294,967,296 or 4.2billion. That’s roughly4GB because 1 Gigabyte is tantamount to 4 billion bits.

Okay, stay with me.  I suck at math but I’m doing the best I can to explain this:

This means the highest address accessible via a 32bit system is 4GB but the hardware has to apportion some of that memory for critical operations such PCI Express support and the BIOS.  The result, is that somewhere between 256MB and 1GB of space below 4GB is set aside for the board and the OS can’t touch it; it’s reserved for hardware.

So what should you do?

You’ll need to get the 64bit version of Windows which means you’ll have to backup up all your files, insert the 64bit Windows media and click the custom install option.

The custom option is synonymous with a clean install.  In other words, you’ll loose all your programs and settings; that’s why it’s really important that you backup your data first.  This might seem like a pain but it’s a really good idea to consider it.

Think about it: with more memory you can open more files concurrently without slowing down your computer and the improvement will be palpable.  You’ll really feel the difference therefore I exhort you to give it a shot.

If you’ve already done so, share your experience in the comments!


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Posted in Desktops, Hardware, How To, Laptops, Windows 7 Tagged with: