The Pentium 4 Prescott core was introduced early last month, and gave us a first look at the 90nm core and its 1-MB of L2 cache. The Prescott was intended to debut at speeds of up to 3.4 GHz, but at the time, we only had the opportunity to evaluate the Pentium 4-3.2E GHz. The overall performance results were a stalemate, with the Prescott core showing legs in some areas, while falling behind Pentium 4 3.2C GHz Northwood in others.
Today we're pleased to present our official review of the Pentium 4-3.4E GHz Prescott, along with our first opportunity to test the Pentium 4-3.4C GHz Northwood, a processor that had been in the market for some time. These two processors are very important to the Intel strategy, as they compete directly against the Athlon 64 3400+, an upstart processor that has given Intel headaches at the mainstream high-end.
The Pentium 4-3.4E is basically a speed upgrade of the Pentium 4-3.2E, and features the new 90nm (0.09-micron) Prescott core. The Prescott is not a departure from the Northwood core, at least on the outside, as it uses the standard Socket 478 package, runs on the 800 MHz front-side bus, utilizes the same basic board and heat-spreader design, and is compatible with many current Intel chipsets like the i875P and i865PE. The Pentium 4-3.4E may be the last Socket 478 Prescott processor, before Intel moves to the LGA775 format and adds a whole slew of chipset features like PCI Express and DDR-II.
The internal architecture is where the Prescott really differs from the previous Northwood core design. The most prominent change has been to double the cache levels, where the Prescott core features a full 16K of L1 cache (8K for the Northwood) and a full 1-MB of L2 cache (512K - Northwood). There are other smaller changes, such as the 8-way associative L1 cache of the Prescott (4-way associative for the Northwood), while the 1-MB L2 cache retains the same 8-way associative format as the Northwood. The Prescott core is built upon a 90nm (0.09-micron) process technology, and will allow Intel to increase clock speeds and lower core voltages more significantly than the older 0.13-micron Northwood core would allow.
The most contentious architectural change is the extending of the Prescott pipeline, in order to facilitate higher frequencies. This strategy presents some challenges, as performance is impacted, but it comes with the benefit of higher clock speeds, and in a much faster timeline. It also brings back those old "AMD vs. Intel" battles where IPC (instructions per clock) is tossed back and forth like a hot potato.
At 3.2 GHz, the Prescott seemed like it was running on the spot. The Intel Prescott core features double the L1 and L2 cache, an extended pipeline, increased latencies, 13 new SSE3 instructions, tweaked internal predictor and prefetch hardware, and increased Hyper-Threading performance, but in many ways, it's a wash. The hardware enhancements do increase performance, but the penalties incurred also take their toll, and at least in the case of the Pentium 4-3.2E GHz, it evened out in the end. We'll have to wait and see how the Pentium 4-3.4E GHz does in the benchmark arena, with special attention paid to how it stacks up to the Northwood models and the Athlon 64 3400+.
