The first year of production for the Pentium 4 has not been the resounding success that Intel would have hoped for it’s top line processor. The original “Willamette” Pentium 4 has never managed to receive anything more than a lukewarm reception from review sites and the PC hardware enthusiast community. Conversely the AMD Athlon and later Athlon XP processor ranges have been greeted enthusiastically by review sites and the PC hardware enthusiast community. As a result the Pentium 4 has not been a hit in the retail PC market. The only place where it has had a good reception is the corporate PC and workstation market which has traditionally had an Intel bias.

Recently Intel did manage to address one of the main problems facing the “Willamette” Pentium 4, which was the lack of an affordable and fast platform upon which to run. Market reception of the original i850 chipset and RDRAM combination was weak due to the high cost of the Rambus memory. The cost aspect of this problem was addressed by the PC-133 compatible i845 chipset, but this left users with less than spectacular performance (especially when compared to Athlon based systems). The problem of performance has now been addressed with the new i845D chipset which allows the Pentium 4 to be paired with PC-2100 DDR (Double Data Rate) SDRAM.

Whilst Intel finally has addressed the platform problem surrounding the Pentium 4, it still needed to address the issue of less than sparkling performance. This is where the new “Northwood”, or Pentium 4 (A) comes in.

Pentium 4 2.2 Ghz, what’s new?

The new Pentium 4 (A) comes in 2.2 and 2.0 GHz flavours (there will also be some 1.6, 1.7, 1.8 and 1.9 GHz chips supplied to OEMs), which for the 2.2 Ghz part offers a 200 MHz speed increase over the fastest “Willamette” part. This though is only part of the natural progression for the Pentium 4 which has been made available by Intel’s move to the new 0.13 micron manufacturing process. Intel for the first time has used copper interconnect technology on the Pentium 4 (A). Whilst this has been a first for Intel, AMD have used copper interconnects on its Athlon “Thunderbird” and Athlon XP ranges since 2000 (i.e. 700 MHz upwards).

The Pentium 4 (A) will only be made using the 0.13 micron process, as opposed to the 0.18 micron process used by the “Willamette” Pentium 4. This process enables Intel to reduce the size of the transistors used by the Pentium 4 and consequently to reduce the overall size of the chip. Overall heat dissipation is reduced by the move to 0.13 micron which consequently allows Intel to further increase the clock speed of the Pentium 4 (A) up to 2.2 Ghz.

As a result of the new smaller die size, Intel has also been able to increase the size of the level 2 cache on the Pentium 4 (A) from 256 KB to 512 KB. This is the first mainstream processor since the Pentium Pro to feature a full 512 KB Level 2 cache integrated onto the main chip die.

As the clock speeds of the Pentium 4 are considerably higher than those on the “Coppermine” Pentium III, the cache latencies have to be much higher in order to run at these speeds. Wheras the Level 2 cache latency of the “Coppermine” Pentium III was a spectacularly low 7 cycles, the “Northwood” Pentium 4 (A) is a much higher 9-18 cycles. This is still better than those of the Athlon XP and older chips such as the “Mendocino” Celeron and AMD K6-III.

Whilst the latencies Level 2 cache on the Pentium 4 (A) are slightly higher than those of the “Coppermine” Pentium III, their effects are more than likely to be offset by its large 512 KB size. Intel engineers have also managed to implement some subtle enhancements to the cache design of the “Northwood” Pentium 4 (A).

Other than the aforementioned enhancements the new Pentium 4 (A) has the same core features as the “Willamette” Pentium 4. These are:

• Hyper pipelined architecture (i.e. 20 stage instruction pipelines)
  
  
• Advanced Dynamic Execution (i.e. improved branch prediction and hardware prefetch)
  
  
• Rapid Execution Engine (i.e. double-pumped ALU, allowing instructions to be processed on the rising and falling edge of the clock cycle)
  
  
• Trace cache
  
  
• 256 KB Level 2 cache
  
  
• SSE2

For a full explanation of all these features please refer to our original Pentium 4 article.

Effectively the Pentium 4 (A) is bearing the fruit of Intel’s NetBurst design philosophy in that a processor with extremely long instruction pipelines is capable of running at extremely high clock speeds. Intel is likely to scale the new “Northwood” Pentium 4 chip to speeds in excess of 3 GHz.

Pentium 4 2.2 GHz - Page 2.