I’ve been preparing for Microsoft’s new Vista operating system and while it was very easy to find the minimum requirements for the new OS, finding the maximum limits has been like searching for a needle in a digital haystack. In particular, I was looking for the maximum amount of RAM that Vista Ultimate Edition can handle. It turns out the REAL answer was harder to discover than I thought. Because for me, how much RAM an OS can REALLY max out at, means exactly how much will I have viewable and addressable within the OS? The official word from Microsoft, is that all 32-bit versions of Vista except the Starter edition have a max of 4GB. (Starter edition can only do a maximum of 1GB.) Microsoft says the 64-bit versions of Vista vary to a greater degree, with Vista 64-bit Ultimate edition maxing out at 128GB. This all sounds reasonable, but for my personal definition of an OS maximum for RAM and possibly your personal definition too, those answers are not exactly true for 32-bit.

I found this post on a blog that is run by a Microsoft MVP. (MVP is one of the higher honors the company might give to a non-employee that is knowledgeable about a Windows product. MVPs usually don’t open their mouths unless they know what they are talking about.) Tony Northrup has found that people are loading their boxes up with 4GB of RAM using Windows Vista 32-bit and the OS can only see between 2GB and about 3.5GB of RAM available. This is because of how Vista 32-bit handles the RAM and it’s fully explained in that post. For me this is disappointing. As I’m sure it is for folks waiting to see 4GB of RAM at their disposal. The RAM that can’t been seen within the OS is being used, but can’t be addressed directly by you from within the OS. So the bottom line for me and maybe you is that you won’t be able to use the whole 4GB of RAM the way you’d like in Vista 32-bit.

Of course Widows Vista 64-bit can see 4GB of RAM with no problems at all, but you’ve got to make sure your hardware can handle addressing more than 4GB of RAM if you want to go beyond that. The Vista package comes with both the 32-bit and 64-bit versions. So you can switch when you wish, but for most of us 64-bit is not a good option for the near future.

And even before you upgrade to Vista 32-bit, you better make sure your programs are compatible. There have been LOTS of complaints. This article mentions one example and there is an entire VistaIncompatible.com Forum, yikes! Here is a list of some compatible software. To make sure your hardware is ready, get the Vista Upgrade Advisor. It looks at programs too, but does not appear to know about a lot of them, judging from my use of the tool.

So that’s the deal and it looks like Tony’s Vista Clues blog is going to be a good resource for any of us considering a move to Vista.

(For the sake of full disclosure, I hold shares of Microsoft stock.)