This article originally appeared on Hardware Central.

It seems like only yesterday when Intel announced its dual-core Pentium Extreme Edition and Pentium D models, and quickly ushered in the era of multiple-core x86 processing. This involves chips with two or more processor cores on the same die, providing true multithreading support (not to be confused with Intel's partial, next-best-thing Hyper-Threading) through a single CPU package.

AMD may have missed being first out of the gate, but the company has outlined its own dual-core release strategy for both the Opteron server/workstation and Athlon 64 desktop lines -- moving quickly to push dual-core, 64-bit-capable CPUs into the mainstream for everything from home PCs to the corporate enterprise.

The Dual-Core Opteron

AMD's x86-compatible Opteron has put Intel's proprietary 64-bit Itanium in a world of hurt, and now the underdog is planning on hitting the Xeon hard. The dual-core Opteron 865, 870, and 875 were announced just the other week with the rest of the lineup due later this month, but preview hardware has already been making the rounds.

AMD currently has a three-tier Opteron lineup, indicated by model numbers in 1xx (1-way), 2xx (2-way), and 8xx (4- to 8-way) series. The dual-core Opterons follow this scheme with higher model numbers; for example, the Opteron 865, 870, and 875 are positioned above the top single-core model 852.

Like Intel with the Pentium D, AMD will release dual-core Opterons at lower-than-single-core clock speeds: The fastest single-core Opteron CPUs currently run at 2.6GHz, while the fastest dual-core chips clock in at only 2.2GHz. This is understandable given production and heat requirements, and in the case of the workstation/server-based Opteron, clock speed shouldn't really be the issue it has been for Intel in the desktop arena. Server and workstation motherboards are expected to have two or more CPU sockets, and the entire platform and software architecture is designed around this.

The Opteron has been AMD's forerunner or first recipient of new technology since its introduction, and there is a valid reason for going with it rather than the Athlon 64 for the initial dual-core release -- software. Mainstream server applications are multithreaded by default, as code is written with multiprocessor environments in mind. This is far different than the desktop area, where multithreaded software is the exception rather than the rule. The server focus will not only help AMD achieve higher market penetration, but also allow the company to post all sorts of glowing dual-core benchmark results.

The Athlon 64 X2

AMD's dual-core desktop chips are a bit further off, with the formal debut of the Athlon 64 X2 expected sometime in June. This release will be more along the lines of the Intel Pentium D, introducing dual-core CPUs at the high end of the desktop market.

It also makes a few refinements over the Pentium D architecture, where Intel's "Smithfield" core is literally two "Prescott" 1MB-L2-cache cores slapped into a single package. The latter does provide multiprocessing, but with no on-die core communication, Smithfield doesn't seem to be built for dual-core from the ground up. The Athlon 64 X2 promises a more seamless design, including an on-die interface between the two CPU cores which will speed up some data transfers significantly.

In theory this should also speed up memory transfers, but that could be mitigated by the basic design. Memory bandwidth is a definite concern when it comes to dual-core processor designs, especially as AMD's and Intel's processor bus designs have remained consistent. Intel requires a whole new platform, while maintaining the same CPU and memory-bus specifications. To ensure backward compatibility, AMD too is sticking with its current bus architecture and dual-channel DDR400 interface. What this boils down to is the same memory bus and bandwidth for two processor cores as we had for one, putting a possible damper on overall memory performance.

The Athlon 64 X2 line also features lower clock speeds than comparable Athlon 64 models, but the difference is only half as much as with the dual-core Opteron: The fastest Athlon 64 X2 will run at 2.4GHz, or just 200MHz lower than the 2.6GHz Athlon 64 FX-55. This is simply amazing, especially since Intel's dual-core Pentium D's top clock speed of 3.2GHz falls well below the single-core Pentium 4 record of 3.8GHz. AMD will also segment the X2 line as it has with existing desktop chips, offering Athlon 64 X2 models with either 512K or 1MB of Level 2 cache, the latter bringing a slightly higher model number and retail price.

If there is one major advantage AMD holds over Intel in this move to dual-core, it's an ironic one -- AMD's lack of Hyper-Threading. Intel introduced the latter technology with the Socket 478 Pentium 4 processors, offering a kind of dual-processor emulation through segmenting of one physical processor. It allows smoother desktop performance during multitasking, but only a small boost for single-threaded applications. Since AMD hasn't had a comparable "one and a half processor" design, the performance jump from single- to dual-core will be much more noticeable on the AMD side than for Intel.

Socket 939 or Bust

AMD deserves special kudos for making the dual-core Opteron and Athlon 64 X2 compatible with current Socket 940 and 939 platforms, respectively, as this really sends a positive message to customers. AMD has declared that only a BIOS update will be required to facilitate a dual-core upgrade, thus allowing Socket 939 motherboards to span perhaps the widest processor selection ever. Motherboard vendors may secretly pine for a platform shift and the resultant new hardware sales, just as deep-pocketed enthusiasts may crave a higher-end memory architecture, but there's something to be said for basic customer loyalty and support -- especially after AMD's initially confusing desktop transition from Socket 940 to 939 and the lingering market presence of Socket 754.