Some of our readers will undoubtedly remember the hype surrounding the Pentium 4 before its launch near the end of 2000. Among a boatload of other speculation, one recurring motif was that the new "NetBurst" architecture was designed to scale very high. At times numbers of "10 GHz by 2005" were being speculated.

Well 2005 is upon us, but 10 GHz processors are nowhere close to being viable by any manufacturer. Intel's fastest Pentium 4 to date is the 670 model, which clocks in at 3.8 GHz and AMD's fastest Athlon clocks in at 2.6Ghz. Both Intel and AMD have had trouble pushing their latest cores any higher than that. What were Intel's original plans, and how have they changed now? Let's take a look.

The first incarnation of the Pentium 4 came in the form of the Willamette core, released in late 2000. Initially, the Willamette came in speeds of 1.3, 1.4, and 1.5 GHz. These first models were the first indication that Intel was serious about ramping the clock speed of the Pentium 4. The 180-nm Willamette lived on until 2.0 GHz, when Intel released a revamp of the core in October of 2001.

The new 130-nm core, dubbed Northwood, finally gave Intel a chance at stealing back the performance crown from AMD, who had snagged it from Intel with their Athlon Thunderbird and Athlon XP processors up until then. Northwood increased the L2 cache size (256 KB to 512 KB), and included a number of other enhancements that allowed it to consume less power, and hence, generate less heat. By all accounts, Northwood was a winner. It allowed Intel to ramp up the Pentium 4 all the way to a 3.4 GHz model, which was released in early 2004. Earlier on in Northwood's life, Intel added an interesting feature which it named "HyperThreading". HyperThreading allowed semi-simultaneous execution of software threads through the addition of a "logical" processor which depended on proper operating system support for efficient utilization. HyperThreading, when used with Windows XP, provided a smoother computing experience, as empty stages in the Pentium 4's long 20-stage pipeline could be filled up.

Knowing earlier on that even Northwood would eventually hit a brick wall in terms of clock speed, Intel began work on the Prescott core. Prescott turned out to be a major re-working of the Pentium 4's architecture, which explained its delays. It included, among other things, the move to a 90-nm fabrication process, the addition of SSE3 instructions, and 10 additional stages to its pipeline. Some analysts speculated that Intel might end up calling the Prescott "Pentium 5". Alas, that was not the case, and Pentium 4 it remained when Intel unveiled the new core on February 1st, 2004.

In all honesty, Prescott did not turn out exactly as Intel had intended. A longer pipeline generally means that the chip ought to ramp higher in clock speed, but Intel seems to have hit a wall at 3.8 GHz. Considering that Northwood hit 3.4 GHz, a 400 MHz increase did not seem to be worth all the effort. Not only that, but Prescott generates a good deal more heat than Northwood did. The heat output of Prescott has actually raised some concerns in the community. There have been reports that the 3.8 GHz model actually clock-throttles itself once it is put under load, due to its own heat output.

The most modern incarnation of the Prescott is the 3.8 GHz model, with 2 MB of L2 cache, running on an 800 MHz FSB, making use of SpeedStep technology, and supporting EM64T (Intel's implementation of AMD's x86-64 instruction set extensions). Originally, Intel had planned a 4.0 GHz model, but thermal problems with Prescott turned out to be so severe that Intel completely scrapped that plan.

That brings us to where we are today. Not only was the 4.0 GHz model scrapped, but Intel has undergone some deep strategy changes. A year ago this month, Intel announced that they would be migrating the Pentium 4 to a dual-core architecture, undoubtedly from pressure by AMD, as well as their own failed Prescott experiment. This pressure from AMD is coming in for a similar reason. AMD was lucky enough to see earlier on that they would have trouble scaling their Athlon 64, and made the strategy-change to multi-processing while Intel still thought they had a chance with big megahertz numbers. Consequently, Intel has gone from pushing clock speed to chasing multi-processing as the way of the future. The first realization of this strategy change has already taken place and was released earlier this month in the form of the "Pentium Extreme Edition 840".

The change is subtle, but it only goes further to demonstrate their altered mentality: the moniker lacks any sign of a "4". Intel used the "Pentium 4" name through multiple core revisions, and now with the new dual core approach, it seems almost fitting that the "Pentium 4" name be dropped in favour of a new label.

The Pentium Extreme Edition 840 itself is the first member of Intel's new dual-core family, which features three other processors:

If you look closely at the table above, you can see that the Pentium D 840 and Pentium Extreme Edition 840 are basically the same chip, with the exception that the EE has HyperThreading enabled. Considering the price difference between the two, I'm not sure this is particular part will be appealing to consumers. Unless the bragging rights of having four CPU graphs in Task Manager is important to you, I can't see any sane person buying the Pentium Extreme Edition 840. But since the EE no longer has a cache advantage (all models have 1 MB L2 per core), Intel has to differentiate it somehow to give it the "Extreme" name. It would still be interesting to see whether 4 cores would make any more differences than 2 in a typical multi-threaded or multi-tasking environment.

While the EE 840 is definitely an impressive beast, today's review will focus on the other end of the spectrum: the consumer-level Pentium D 820. Priced at a mere $241, it is painfully obvious that Intel is trying to steal both thunder and purchases away from AMD, which has been hyping its own desktop-oriented dual-core processor, the Athlon 64 X2. We reviewed the Athlon 64 X2 4200+ here just a few days ago. With the Pentium D 820 priced at less than half of what AMD's entry-level dual-core part is priced at, Intel could very well be responsible for initiating the dual-core push into the consumer home.

Let's now take a look at Intel's approach to their dual-core architecture.