I ran into a little problem today. One of my test servers which has 4GB of RAM was giving me an error on boot. This error indicated that I only had 256MB of usable memory.
Well, low and behold, Dell has a setting in their BIOS called “OS Install Mode”. When set to On, memory is limited to 256 MB to allow the installation of older operating systems that have 2 GB memory limits. I had never heard of such a thing, but those servers run a lot faster with it turned off, especially when you have 4GB RAM!