Celeron Willamette is a 7th generation processor based on Pentium 4 Willamette core. It uses the FC-PGA2 packaging and is installed on socket 478 motherboards. It is important to remember that the first Pentium 4 models used socket 423 motherboards and no version of Celeron was launched for this kind of socket.

The architecture of Celeron Willamette L1 cache is completely different from other Celeron models presented until now, being based on the same architecture used by Pentium 4 processor. Instead of having a L1 data cache and a L1 instruction cache, this Celeron version has a 8KB L1 data cache and a trace execution cache.

The trace execution cache is located between the instruction decoder and the execution unit and is used to store the instructions already decoded. This cache stores up to 12 K microinstructions. Since each microinstruction has approximately 100 bits, this cache unit stores around 150 KB of data.

Another difference between this Celeron model and the previous ones is that it uses a 256-bit data path to communicate with its L2 memory cache, while this communication was previously done using a 64-bit or 128-bit data path.

Another important detail regarding Celeron Willamette is about its external bus operation. Celeron Willamette transfers not only one, but four data per clock pulse. So, the performance of its external bus is four times higher than a conventional external bus which runs with the same clock. Celeron Willamette works externally at a speed of 400 MHz (100 MHz x 4) reaching a theoretical maximum transfer rate of 3.2 GB/s.

Celeron Willamette was built using a process of 0.18 µm. It gives support to SSE2, and is available on versions ranging from 1.7 GHz to 1.8 GHz.

Figure 7: Celeron Willamette with FC-PGA2 packaging.

Figure 8: Celeron Willamette external bus works transferring four data for each clock pulse.

The only difference between Celeron Willamette and Northwood resides in the fact that Celeron Northwood is based on Pentium 4 Northwood core and was built with a technology of 0.13 µm. Everything said about Celeron Willamette is also valid for Celeron Northwood, which is available in clocks ranging from 2.0 GHz to 2.8 GHz.

Main features of Celeron Willamette and Northwood were:

• Based on Pentium 4 with Willamette core (models up to 1.8 GHz) or Northwood core (models starting at 2 GHz)
• Manufacturing process: 0.18 μm (for models based on Willamette core) or 13 μm (for models based on Northwood core)
• L1 cache: 8 KB for data and 150 KB trace cache
• L2 cache: 128 KB
• External clock rate: 400 MHz (100 MHz transferring four data per clock cycle)
• Packaging: FC-PGA2
• Socket: Socket 478
• Added support to SSE2 instructions, keeping support to SSE

Available models of Celeron Willamette and Northwood are listed on the chart below. TDP stands for Thermal Design Power and indicates the CPU maximum thermal dissipation.