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  P4 2.53 GHz & Intel 850E, The Pentium 4 Gets A New FSB 
  May 06, 2002, 10:00am EDT 

Speeding Up The Pipe

By: Dan Mepham

Intel’s Pentium 4 processors have used a 400 MHz (100 MHz Quad-Pumped) Front Side Bus since their introduction. Today, Intel is bumping that bus up to 533 MHz (133 MHz Quad-Pumped). The increase in clock speed provides over 4.2 GB/s* of bandwidth between the processor and MCH, up 33% from the previous 400 MHz bus.

Intel is introducing three new Pentium 4 processors based on the Northwood core, which clock in at 2.26 GHz, 2.40 B GHz (the ‘B’ notation of the latter serves to differentiate it from the 2.40 GHz part using the 400 MHz FSB), and 2.53 GHz. The 2.26 GHz part will be priced equal to the 2.20 GHz Pentium 4 using the 400 MHz FSB, while the 2.40 B GHz part will likewise be priced identically to its 400 MHz counterpart. The 2.53 GHz part will be Intel's flagship for the time being, and as such will carry a flagship-level price. Expect a 3.0 GHz part to appear before the end of the year.

Some may note that, typically, Intel’s higher bus speed parts are initially priced slightly higher than the lower bus speed parts. We’ll see why this isn’t the case this time around shortly.

Naturally, processors with a faster Front Side Bus require a supporting chipset. That chipset comes in the form of the Intel 850E, which is, for all intents and purposes, the original 850 chipset validated for use at 533 MHz. The new 850E chipset consists of a new MCH, part numbered 82850E, and the same ICH2 seen on the original 850 chipset, part numbered 82801BA. The 850E MCH is completely pin-compatible with the 850 MCH, and aside from documented and validated support for the 533 MHz FSB, contains no other architectural enhancements. Since the 850E chipset uses the same I/O Controller Hub as the 850, I/O functionality (such as PCI, USB, IDE, etc) remains unchanged.

*The Pentium 4’s Front Side Bus is 64-bits wide, and operates on a 100 or 133 Mhz core frequency. The bus is ‘Quad-Pumped’, or capable of transferring four times per clock cycle. This translates to an effective speed of 400 MHz or 533 MHz clockspeed, delivering 3.2 GB/s or 4.26 GB/s of bandwidth, respectively.

100 MHz * 4 Transfers/Hz * 64-bits / (8-bits per byte) = 3,200,000,000 bytes/s = 3.2 GB/s
133 MHz * 4 Transfers/Hz * 64-bits / (8-bits per byte) = 4,266,000,000 bytes/s = 4.266 GB/s

1. Introduction
2. Speeding Up The Pipe
3. More Memory Bandwidth?
4. Testing Methodologies
5. Performance - Cache & Memory
6. Performance - Audio & Video Encoding
7. Performance - Scientific
8. Performance - Gaming
9. Performance - Professional OpenGL
10. Summary

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