Problem: “I bought a computer with 4 gigs of ram memory. However, Windows only shows 3 gigs. Where is the other gig of ram?”

There could be several reasons for this:

1. Some computer motherboards have a bios chip that will only allow the system to recognize a certain amount of ram. We saw a system two weeks ago with 2 gigs of ram installed, but the bios would only recognize 512 megs per bank for a total of 1 gig. This limitation was created by the manufacturer as a 32 bit Pentium processor can recognize 4 gigs of ram.
2.  
3. In another case, just last week, a new computer showed 3 gigs of ram in use whilst the system bios correctly showed 4 gigs installed. This system, like many built today, uses something called “memory mapped IO reservations,“ which means some of the memory is reserved for use by system hardware, caching, or dynamic video memory. If, for instance, you have 4 gigs of ram but Windows reports 3.5 gigs of ram, .5 gigs or 512 megs is being used or reserved for computer hardware use and cannot be accessed by Windows.

A Pentium 4, is a 32 bit processor with 32-bit register has memory 232 addresses, or 4 GBs of RAM, could be referenced.

A Dual Core is a 64 bit processor effectively increases the memory ceiling to 264 addresses, equivalent to approximately 17.2 billion gigabytes, 16.8 million terabytes, or 16 exabytes of RAM.

However, there are several issues with 64 bit computers:

1. Most 64 bit computers have artificial memory limits between 2 and 8 gigs
2.  
3. 64 bit Vista is buggy and more expensive
4.  
5. You must use 64 bit versions of your favorite software – expensive and buggy.

If you feel the need to have 4 gigs of ram, make certain your hardware will supporting before turning loose of the coins.

For a full explanation, please try the following links:

http://blogs.msdn.com/hiltonl/archive/2007/04/13/the-3gb-not-4gb-ram-problem.aspx