Marshall Brain's Blog

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Intel's Prescott chip - the latest Pentium 4

There have been hundreds of articles this week on Intel's latest version of the Pentium 4 processor. For example:

• Intel Launches Prescott; 64-Bit Question Unanswered
  
  
• Prescott flunks benchmark tests
  
  
• Intel's New Weapon: Pentium 4 Prescott
  
  
• Intel Aims for Desktop with Prescott, But Hits Servers, Too

Here's a quick set of statistics and factoids on the Prescott chip culled from all of these articles:

• The Prescott chip breaks the 100 million transistor barrier, with 125 million transistors on the die.
• It is made with a 90 nanometer (nm) process.
• It is made on wafers that are 30 cm (almost 12 inches) in diameter.
• The die size is about 10.5 x 10.5 mm, or 112 square millimeters (even though the number of transistors is way up, the die size actually shrank from previous P4s).
• So each wafer holds 588 processors. As yields rise, this should mean inexpensive chips.
• Current speed max is 3.4 GHz, with 4.0 GHz promised by the end of the year.
• The L2 cache is 1 MB, the L1 cache is 16 KB (both doubled).
• It has a 31 stage pipeline (up from 20) which should make it easier to increase clock speeds in the future.
• There is some speculation that new 64-bit instructions are hidden on the chip but are not yet activated -- the large increase in the number of transistors is not all accounted for by the larger caches.
• This article points out that "The Prescott system tested dissipated significantly more power than comparable chips under a full load, coming in at nearly 250 watts, compared with nearly 200 watts for a Northwood system and about 168 watts for a comparable Athlon64 system."

Intel appears to have big changes planned for later in the year. For example, it will be moving from the current 478-pin format to a 775-pin format, there will be a new chipset (Grantsdale)and therefore a new bus (PCI Express), new memory, etc. Possibly with all of these changes, it will be renamed the Pentium 5 and the 64-bit instruction set will become available.

In November of 2000, the Pentium 4 was running at 1.5 GHz and using a 180 nm process. The chip had 42 million transistors. Now, about 3 years later, the clock speed has more than doubled and the number of transistors has tripled. Intel has already announced a new technique that will allow it to significantly cut heat dissipation as it moves to a 45 nm process. So by 2010, it would not be surprising to see 10 GHz processors with 500 million transistors (this presentation given by Intel in 2003 is even more aggressive -- 1.8 billion transistors and 30 GHz by 2010).

At some point, as power dissipation decreases and the transistor count goes way up, it would not be surprising to see multiple CPUs on a single chip. At 45 nm Intel can put two or four complete P5 chips on a single die, or as many as 10 P4s. 10 P4s running at 10 Ghz would provide something on the order of 100 billion operations per second. That would be a way to significantly increase performance in a desktop machine. Another option is massive parallelism. For example, the GumStix computer uses a 32-bit PXA255 processor running at 400 MHz. With 64 MB of RAM, it dissipates only a watt. It currently uses a 350 nm process and has 2.6 million transistors. You could fit almost 200 of these onto a 500 million transistor die.

2010 should be a very interesting year...