For years, Intel and AMD marked their progress in the microprocessor market by ratcheting up the clock speed of their products. But eventually, it became difficult to increase the raw speed of their chips without overheating the entire system. A few years back, Intel took the first steps toward more efficient microprocessors with the release of such technologies as HyperThreading (HT) Technology and the Centrino chipset, and AMD offered up its 64-bit AMD-64 technologies. Today, both companies are pioneering a new generation of better-performing microprocessors that bring much more than raw horsepower into play. Here's what you need to know about Intel and AMD 2005 microprocessors.

Dual-Core
When Intel and AMD began offering dual-core microprocessors, the chips were in high-end products only, with Intel targeting the high-end gaming market with its expensive Pentium 4 Extreme Edition (Pentium 4 EE) and AMD aiming at the server market with dual-core Opteron chips. Today, both companies also offer dual-core chips for mainstream desktop users. Intel's Pentium D processor and the AMD Athlon 64 X2 processor are widely available and will become the companies' main desktop offerings by the end of the year.

Dual-core chips have two true microprocessor cores, each with dedicated L2 cache. The performance benefits of these systems are astonishing. Unlike HT microprocessors, which could add to or detract from overall system performance depending on the circumstances, dual-core microprocessors provide almost exactly the same performance as a system that has two separate microprocessors. (For one performance comparison, see Digit-Life.com's analysis at http://www.digit-life.com/articles2/cpu/intel-cmp-vs-smp.html.) But dual-core systems run cooler and consume far less electricity, allowing for smaller, quieter, more efficient PCs.

x64 Compatibility
AMD pioneered x64 technology, which adds 64-bit capabilities to x86-compatible microprocessors, but Intel adopted the technology in early 2004 and now offers it across all its mainstream microprocessors. Chips such as the Intel Pentium D and AMD Athlon 64 offer x64 compatibility today, as do most of the companies' other processors.

What x64 compatibility buys you is future-proofing: In addition to providing for up to 1TB of RAM, x64-compatible processors can handle data in 64-bit chunks. Both features dramatically improve a PC's performance, assuming you're running a 64-bit OS, such as Windows Server 2003 x64 Editions or Windows XP Professional x64 Edition, and, preferably, 64-bit applications. But x64 systems also provide slightly better performance than equivalent x86-based processors when running 32-bit OSs, so you can upgrade hardware now and move to 64-bit software systems later.

AMD and Intel Face Off
With the release of mainstream dual-core x64 microprocessors from both companies in mid-2005, hardware testers began comparing the relative performance of each chip. Early results, such as those obtained by Tom's Hardware Guide (http://www.tomshardware.com/cpu/20050603/), indicate that the Athlon 64 X2 outperforms the Pentium D and Pentium 4 EE by a slight margin overall. AMD's chips tend to be faster on a per-application basis, whereas Intel's have performed better in heavy multitasking tests.

There are other tradeoffs. AMD chips tend to be more expensive than Intel's, but they also consume less energy.

Recommendations
My recommendation is to forego single-core chips that don't offer x64 compatibility at this time. Even if you don't need x64 capabilities now, you'll likely want them in the future, and a dual-core chip outperforms a single-core chip running at the same clock speed. Decisions about whose processor to use are largely either religious or moot, as most PC companies offer only one chip type. You can't go wrong with a dual-core x64 microprocessor regardless of who makes it.