Clearly, we have finally reached the limit of the 32–bit processor architecture. 32–bit processors can address exactly 4GB of memory, in an ideal world. The problem is not that your average app will require a lot of memory, but that the total of all your applications will require more than 2–3GB. In reality, some of the address space is reserved (but not used!) for I/O, so you can’t have the full 4GB. The net result is that you can use roughly 3GB of memory on 32–bit Windows XP. If PAE (Process Address Extensions) is not enabled, you are further limited to 2GB per process (this is a Windows imposed limitation). It looks like PAE is enabled automatically on Windows XP SP2 when you have 2GB of RAM or more, at least on my machine.

Modern PC with Vista, everybody seems to agree, will work well with 2GB of RAM. If you want to run a VM or two, you should probably install 4GB (or more, if your motherboard supports it). The same limit of about 3GB usable applies to 32–bit Vista too, which leads us to the only reasonable choice: 64–bit Vista.

Several years ago when AMD built the first desktop 64–bit processor I was really excited about the transition to 64–bit. Some of the business apps I had the chance to work with even required 64–bit machine, mainly because of huge memory requirements. But the transition was slow and especially 64–bit Windows XP did not spread as fast as I expected.

What prevents new operating systems from spreading fast is the driver support. Things are even worse with 64–bit OS-es because they require separate drivers. Microsoft has even stricter requirements for 64–bit Vista: all drivers must be signed. Good thing with Vista is that Microsoft requires from driver manufacturers to certify both 32–bit and 64–bit versions of the driver to get the “Vista ready” logo. Indeed, it took a couple of months (ignore the launch date of 31^st of January, Vista was done in November 2006) but there are Vista certified 64–bit drivers for all of the devices on my mainboard. Good thing is that I don’t have scanners, printers or other esoteric peripherals to worry about. If you do and you’d like to run 64–bit Vista, make sure there is a driver for your device first.

As soon as VMWare 6 goes out of beta, I’ll move my current installation of Windows XP into a VM, install 64–bit Vista and enjoy 64–bit goodness. It is amazing how technology allows scenarios previously unheard of – with the VMWare Converter, I am moving my complete setup, 32–bit Windows XP SP2 with all the drivers and apps installed, into a virtual machine that will continue working even after I wipe out the drive and install a completely new OS.