Pentium 4 2.4 Ghz, what’s new?

Above January’s release of the “Northwood” Pentium 4 running at 2.0 and 2.2 Ghz, the new 2.4 Ghz chip represents a 200 MHz speed increase. In many respects the 2.4 GHz chip is famous for what it is not. It does not use the new 533 MHz bus (due in May) and does not use a 10% shrunk core as was alluded to in the IT news only a week before its release. In essence it is a new, faster “Northwood” chip.

The Pentium 4 2.4 GHz 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.

Interestingly though, Intel has pointed out in its press release accompanying the new Pentium 4, that there are a number of components inside this chip made using a 0.006 micron process. How much this will impact the future headroom growth for Intel can only be estimated (i.e. what will they do for some components when they reach a 0.06 micron process for the chip overall). Does this effect other “Northwood” Pentium 4 chips?

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. The impact of this additional cache has had the effect of significantly improving performance.

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 2.4 GHz 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.

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