Windows Vista Performance Guide

Memory in Vista: How much do you need?

Meeting with memory makers has been fun these past several months - they're all so happy. It's a stressful business, but these days the memory makers are quite excited about Vista and after using the OS for a while now we can understand why. You've undoubtedly been hearing that Vista's memory requirements will be greater than those of XP, but how much greater are they in practice and why?

First and foremost, Vista's memory requirements are higher than XP's simply because there is much more to Vista than XP. There are far more background tasks to take care of, a much more complex UI, and a code base that's significantly larger than that of Windows XP. All of these items require memory, and thus when you boot up a Vista machine with 512MB of memory, almost all of it is already being used.

Microsoft and software makers in general are notoriously bad about understating minimum system requirements, so when you see that the bare minimum requirements for Windows Vista list a system with 512MB of memory, you should know right off the bat that this isn't going to be a pleasant experience. Although Vista will do its best to disable background tasks and neat effects to make using your computer less painful with 512MB, we simply wouldn't recommend it. You can get by running a single application, such as IE7 or Outlook, but multitasking is out of the question. In one of our test scenarios we had four applications open and attempted to close one of them. This process took around 2 seconds if we had 2GB in the system, but it took over 12 seconds if we only had 512MB. Most of us really don't like using Windows XP on a system with only 512MB, and needless to say Windows Vista turns that dislike into outright hatred. Windows XP is more tolerable with 512MB, but we would make a very similar characterization about the overall experience on a system with such little memory.

The experience completely changes with 1GB; the improvement is tremendous. Searches appear quicker, applications launch and close faster, and using the OS is just so much better. Once again, we're not telling you anything you haven't heard before, except that 1GB should really be the minimum for any Vista machine and not just those that are Premium certified. Even our budget Buyer's Guides have recommended at least 1GB of RAM for over a year, and Vista pretty much makes that a requirement.

It's the above-1GB range that really has most of us concerned. For the longest time, 1GB was sufficient for most enthusiasts under XP. As applications and usage models got more demanding, and as memory prices dropped, the move to 2GB made sense. Above and beyond 2GB never really made a lot of sense because Windows XP didn't seem to do much with the added memory. Even if you had unused memory, Windows XP didn't really make the most of it resulting in even recently used programs being paged in from disk instead of loaded out of the main memory cache. Vista changes all of this.

If your memory usage under XP kept you just under needing more than 2GB, you'll need 2GB with Vista. We took two identical installs, one with Windows XP and one with Vista, both equipped with 2GB of memory and ran the following scenario on them:

We opened 104 images in Adobe Photoshop CS3 from our recent trip to Las Vegas for CES 2007; with all 104 images opened and loaded, we then timed how long it would take for Microsoft Word to start. In Windows XP, despite some swapping, Microsoft Word 2007 started in just under 8 seconds. On our Vista test bed, starting Word took almost 20 seconds due to constant paging to disk. The only difference? Vista's heightened memory requirements took a stressful situation that worked reasonably well under XP and made it far more painful with the same amount of memory.

We then upgraded the Vista machine to 3GB and ran the test again; thanks to faster application load times and intelligent prefetching, Word started in 1.31 seconds. If you thought that 2GB was the sweet spot for Windows XP, chances are 3GB will be the new minimum for you under Vista.

Thus far all we've talked about, at a high level at least, are static memory requirements and how they are impacted by Vista. Vista uses more memory and in turn, you'll need a bit more memory to get a similar experience to what you had under XP. With SuperFetch however, Vista can actually significantly improve your system's performance if you throw more memory at it.