This article originally appeared on Hardware Central.

The impending 64-bit revolution has been somewhat deflated by the deluge of dual-core processors from Intel and AMD, a technology that has taken up the majority of recent headlines. And for good reason, too: The advantages of a 64-bit desktop are more ethereal and focused on the future, while multicore processors offer significant performance increases using today's 32-bit operating systems and multithreaded software.

However, a mainstream 64-bit OS is now available in the form of Microsoft's Windows XP Professional x64 Edition, which can be purchased in OEM form or bundled with new 64-bit PCs. This long-delayed 64-bit platform is actually proving quite popular with enthusiasts, especially since Microsoft has introduced a trade-in offer for "old" 32-bit copies of Windows XP.

The combination of mass-market hardware and software is creating not only a groundswell of demand, but also a mindset that 64-bit capability is a check-list feature when choosing a new PC. This has led to a new series of AMD and Intel CPUs that not only embrace 64-bit technology, but also make it affordable for all.

The Stealth-Release Sempron 64

AMD pioneered the 64-bit desktop with the Athlon 64 CPU in the fall of 2003, but until now AMD64 support has been limited to high-end and mainstream rather than budget configurations. But though it hasn't yet made an announcement or held a launch party, AMD has published prices for five new, 64-bit-enabled members of its entry-level Sempron processor line.

In terms of processor architecture, the shift from 32 to 64 bits is not that big a stretch, as the 754-pin Sempron is really just a scaled-down Athlon 64 anyway (and a current Athlon 64 to boot, so the Sempron 64s get not only AMD64 technology but NX-bit virus protection, SSE3 multimedia instructions, and other performance and feature enhancements).

This transition makes 64-bit processing a ubiquitous feature in the AMD world, for customers ranging from low-budget beginners (the new Semprons) to elite enthusiasts (the Athlon 64 FX and X2). And the AMD64 initiative doesn't stop at the desktop, with an extensive line of 64-bit solutions including the Opteron for servers and workstations and Turion 64 for notebooks.

The 64-Bit Celeron D

Intel has made a similarly quiet but significant addition to its value line of Celeron D processors -- six new models with the company's AMD64-equivalent Extended Memory 64 Technology (EM64T).

Aside from EM64T and Execute Disable Bit virus protection (the latter already seen in the 32-bit Celeron "J" chips), there don't seem to be other architectural changes, as the newest Celeron D parts share their predecessors' 90-nanometer-process architecture, 256K of Level 2 cache, 533MHz front-side bus, and LGA775 packaging. The only clues are model numbers one point higher than their same-speed 32-bit siblings, as with the Celeron D 350 (32-bit) versus 351 (EM64T), the current top of the line at 3.2GHz.

We should also be seeing a 3.33GHz Celeron D EM64T later in 2005, and potentially a 3.46GHz part soon after. Official prices are slightly higher than the 32-bit Celeron models, but so far availability is extremely low and it will take some time to get a read on retail prices. Savvy consumers seem to be demanding 64-bit capability in their new desktops, so these CPUs may be in short supply for some time.

Turning on the Turion 64

As mentioned earlier, AMD has also moved 64-bit computing into the mobile market with the Turion 64. Now playing in HP's Compaq NX6124 notebook, the Turion is basically a lower-power version of existing Athlon 64 technology, with all the standard features such as a 90-nanometer core, integrated memory controller, HyperTransport bus, 512K or 1MB of L2 cache, and newer core features like SSE3.

This is an important move since Intel does not have a mobile EM64T processor -- indeed, its popular Pentium M and Celeron M parts are based on the old Pentium III architecture. And with the deletion of the Pentium 4 NetBurst models from Intel's mobile lineup, it may be awhile before we see either EM64T or Hyper-Threading in an Intel-based laptop. So while Intel's Centrino platform arguably offers the best combination of power savings and performance today, the company has left itself open to technological innovations by AMD tomorrow. The Turion 64 provides comparable performance to a similarly clocked Pentium M, but its architecture translates into greater scalability in the future.

Obviously, the current real-world need for 64-bit mobile computing is even smaller than that for 64-bit desktops, but AMD is primarily marketing the Turion 64 as a 32-bit powerhouse that includes all the cutting-edge features, such as enhanced virus protection and power-saving modes (allowing the firm to retire its 62-watt Mobile Athlon 64 in favor of 25- and 35-watt Turion models). The "ready for 64-bit migration" label is the carrot that seals the deal, offering enhanced longevity to a mobile computing market that has enjoyed very little.

The War of the 64-Bit Worlds