When buying a computer, consumers tend to fixate on raw processor speed. However, Photoshop also makes heavy demands on random access memory (RAM) and hard drives. Whatever system you choose, it will be most productive with Photoshop when the capabilities of the processor, RAM, and disks are balanced so that none of the three is an unnecessary bottleneck for the other parts.
Choosing a Platform
Discussions of Macs versus PCs usually tend to degenerate into "my dad can beat up your dad"—spats that produce a lot of heat but little light. Most of the hardware and software you'll need for Photoshop is platform-independent, and we're firmly convinced that when you look at the big picture, price and performance are about the same on the two platforms. The Mac tends to be simpler to operate and easier to maintain. The PC has a greater range of hardware options and general business software.
The bottom line: If you're happy with your current hardware platform, there's probably no reason to switch. You may want to think about upgrading if your machine is more than three or four years old, however. Photoshop CS4 and the latest operating systems make heavy demands on hardware.
If you're planning to upgrade to Windows Vista or Mac OS X 10.5, do yourself a favor—get a machine that was designed with the new operating system in mind. You'll save yourself a ton of time and frustration by doing so. It's possible to run Photoshop CS4 on fairly old machines—the minimum Mac OS requirement is Mac OS X 10.4.11, and the minimum Windows requirement is Windows XP with Service Pack 3—but we can tell you from bitter experience that it can be an uphill struggle. If your time is worth anything to you, trying to run an application like Photoshop CS4 on an outdated machine is a false economy.
Many Photoshop operations involve major number-crunching, so the speed of your Mac's processor makes a big difference. Photoshop CS4 unequivocally demands at least a G5—it won't run at all on anything less. Although the G5 towers were powerhouses in their day, the multiple-core, Intel-based Macs now outpace them.
Photoshop CS4 requires a Pentium 4-class machine, but it's distinctly happier on an Intel Core 2 Duo or Intel Xeon. If you have a 64-bit machine and want to take advantage of more than 2GB of RAM, Windows Vista 64 is highly recommended.