2GHz and counting...
As witnessed by today's 2GHz Pentium 4 launch, Intel's NetBurst microarchitecture is living up to its mission of bringing high performance and clock speeds to the desktop PC. In nine months Pentium 4 has scaled 600MHz, quite a feat in comparison to its predecessor, Pentium III.
Of course, by now we all know the primary reason Pentium 4 has scaled so high this quickly: its twenty-stage pipeline performs less work per clock cycle in exchange for higher clock frequencies. While this means the Pentium 4 does less in each stage of the pipeline, in exchange the Pentium 4 can scale to higher clock frequencies much easier than its predecessor when built on the same manufacturing process.
This long pipeline does come with some negatives. For instance, the performance penalty of a mispredicted branch instruction is much more severe on Pentium 4 in comparison to Pentium III. We discussed this in greater detail in our Pentium 4 Performance Preview, so head on over there for a more detailed description.
Another negative can be directly derived from the processor's clock frequency itself. At lower clock speeds, Pentium 4 offers hardly any performance increase over Pentium III, much less AMD's Athlon processor at 1.0GHz. From a performance perspective, things really don't begin to get interesting until you hit clock speeds greater than 1.5GHz. Fortunately, with the launch of the 2.0GHz Pentium 4, Intel will slowly begin to phase out its 1.3GHz and 1.4GHz processors. This makes 1.4GHz the new baseline, a speed we're much more comfortable with.
Athlon: Still at 1.4GHz
As the Pentium 4 has scaled higher and higher, AMD's Athlon has been lingering at 1.4GHz. In that time Intel has released its 1.8GHz and 1.6GHz Pentium 4 processors, as well as today's 2.0GHz and 1.9GHz P4s. Quite simply, it appears that AMD's Thunderbird core has reached the limits of how far it will go. This is a bit surprising as many enthusiasts (us included) have had no problems hitting speeds of 1533MHz or greater with Thunderbird. Perhaps AMD feels that the yields at higher clock speeds aren't adequate enough to build the parts in sufficient volume. Or perhaps they feel today's market conditions simply don't justify building a 1.5GHz part built on their Thunderbird core. Whatever the reason, we're clearly beginning to see the limits of the core, as Pentium 4 continues to scale to higher clock speeds. With a 600MHz clock speed deficiency, Athlon 1.4GHz is going to have a hard time keeping up with Intel's latest P4.
Besides the new clock speed, the 2.0GHz Pentium 4 sports another new feature -- Intel's 478-pin packaging!