They say that you can never have too much memory (in your PC), but with 32-bit Windows XP and Vista you can.

On machines with more than 3GB of RAM, Windows XP and Vista will report total System memory (RAM) of less than 4GB, often considerably less.

So why is this? Oversimplified, ranges of physical memory are shadowed to support devices in a PC, and above 3 GB larger chunks of memory are used. Daniel Rutter explains it quite well on his Blog “Dan’s Data” in the article “Ask Dan: What’s with the 3Gb memory barrier?“.

The Microsoft knowledge base article No 929605: “The system memory that is reported in the System Information dialog box in Windows Vista is less than you expect if 4 GB of RAM is installed” explains how memory above 3GB is used. Naturally Vista Service Pack 1 has a fix - knowledge base article no 946003: “Windows Vista SP1 will report 4 GB of system memory (RAM) on systems that have 4 GB of memory installed“. Of course this is “a reporting change only“, so the actual amount of RAM is reported corrected, but large chunks above 3GB are still used in the same way.

Basically what this all boils down to is that on a 32-bit Operating System, more than 3GB of RAM is a waste. So the HP (Hewlett-Packard) Pavilion dv9810us Notebook with 3GB of RAM has enough RAM, not too much.

Posted on May 5th, 2008 by mervyn