Why Vista needs 4GB of RAM

Vista is a pig. It's a voraciously greedy resource hog that gobbles up more system resources than any previous operating system. That much is well documented.

It's baffling to note, therefore, that PC-buying punters remain seduced by the big, computational beasts of the component jungle. All too often, PCs are specced up with snazzy CPUs and graphics cards while scant regard is paid to that other performance-critical resource: system memory.

Every year, the likes of NVIDIA, Intel and AMD pour hundreds of millions of dollars into the development of bigger, better and faster chips. There's a similar investment in marketing, promotion and general punter prodding. Admittedly, it'd be easy to draw the conclusion that raw computing power is what you really need.

Improve your memory

But when it comes to day-to-day performance in Windows Vista, it's arguable whether such transistor-heavy chippery makes a significant difference. Put another way, you can throw as many CPU cores as you like at the problem of sludgy Vista performance. And you can wire up any number of 3D boards in multi-GPU rendering mode. If your rig doesn't have enough system memory, it's all for nought.

Conventional wisdom has it that 2GB of system memory is the price/ performance sweet spot for Windows Vista. But we're going to have to kick conventional wisdom out of bed on this one. For starters, he's a smelly old beast that feeds on lazy assumptions. But more to the point, he's just plain wrong. Anyone who has significant experience of Vista running with 4GB of RAM can tell you that. Vista runs much, much more smoothly with 4GB.

So, why the lack of focus on system memory despite the arrival of Microsoft's most resource-hungry operating system yet? Part of the explanation probably stems from the fact that demonstrating the benefits of slamming in the RAM isn't easy. Firing up a single benchmark application and letting rip does not get the job done. To prove our point, a slightly more sophisticated approach is required.

So how much do I need?

But if having heaps of RAM on hand is broadly a good idea, exactly how much do you need? Current conventional wisdom suggests 1GB is the absolute bare minimum for Vista while 2GB is the sweet spot in terms of bang for buck. Indeed, if you are currently enjoying a recently configured rig, there's a very good chance you are running 2GB.

That's plenty for operating systems with relatively modest memory footprints like Windows XP and Linux. But we're here to tell you it ain't enough for a really smooth experience in Vista. What's more, memory prices are now at ridiculously low levels – for old-school DDR2 DIMMs if not the latest DDR3 kit. Even a top-notch matched pair of 2GB DIMMs (4GB in total) boasting extreme cooling can be had for only £75.

So, let's not have any excuses. Compared to a powerful video card or CPU, trimming out your rig with 4GB is now eminently affordable. Before we look in detail at the benefits, however, there is one complicating issue that needs to be addressed. It involves the memory addressing limitations of the 32-bit build of Vista.

Four into 32 goes

In simple terms, all 32-bit operating systems hit the wall in terms of memory address space at 4GB. That's a function of the mathematics of 32-bit computing (for those who care, 32 binary bits can be represented in the decimal system as 232 or 4,294,967,296).

Unfortunately, things get significantly more complicated when 4GB is actually installed in a PC running a 32-bit operating system. Thanks to a feature known as memory mapped I/O reservations, not all 4GB are available for application and operating system use. Instead, some is reserved for certain hardware devices, to ensure driver compatibility, etc.