Parent: Processor Architectures

Intel and AMD Historical, Pentium 4, AMD Opteron, Dual Core, Pentium M to Core 2, Nehalem, Sandy Bridge to Haswell, Hyper-Threading, SIMD Extensions

First Generation Pentium 4

Willamette was the codename for the first brand new micro-architecture after Pentium Pro, a 180nm process with 42M transistors, coming out in late 2000 as the Pentium 4, with a key architectural feature called NetBurst (see The Microarchitecture of the PentiumŪ 4 Processor).

Willamette, 2000 Nov, 180nm, 217mm2, 256K L2

The Pentium 4 architecture was meant run at very high clock rates. The very high clock rate on the Pentium 4 is achieved with a very deep pipeline, that is, each operation is divided into many very small steps. There are 20 pipeline stages in the first generation Pentium (Willamette and Northwood) and ~31 for the second generation (Prescott and Cedar Mill), compared to 10-12 on Pentium Pro to Pentium III line, 12 stages for integer and 17 for floating point on the Opteron and 14 for the Core 2. The Itanium 2 has 8 pipeline stages, but can execute 6 instructions simultaneously.

The Pentium 4 bus was an improved version of the Pentium Pro bus. The clock rate was 100MHz, but addresses count be sent at 200MHz and data was quad-pumped for 400MHz. The APIC controller were brought from a separate bus on to the main bus. During the early Pentium 4 bus architecture time, it was too early to consider point-to-point signaling that was gaining acceptance as the next generation technology. Once Intel did commit to the Pentium 4 bus, they decided to leverage the infrastructure build around it for a along time. All NetBurst architecture processors: Willamette, Northwood, Prescot and Cedar Mill, all the Pentium M architecture processors: Banias, Dothan and Yonah and the Core 2 architectures processors employed the Pentium 4 bus architecture, with the data transfer rate pushed to 1600MHz at the terminal end.

To realize the full benefit of the very deep Pentium 4 pipeline, the code sequence must be very predictable. Otherwise the pipeline gets flushed too often, and the Pentium 4 is no better than other processors running at lower clock rate. The Pentium 4 tended to have uneven characteristics relative to other architectures across a range of applications.

The 4-way server variant codename Foster became Xeon MP in Mar 2002. Apparently Intel could not get a worldwide registered trademark for Xeon, hence the earlier processor were Pentium II or III Xeon. So apparently, Intel was eventually able to secure the trademark worldwide.

Northwood was the codename for the 130nm Pentium 4, released in Q1 2002, L2 cache increased to 512K, 55M transistors. The MP version was Gallatin, initially with 1 & 2M L3 cache in Nov 2002, and a later version with 4M L3 cache.

Northwood, 2002 Jan, 130nm, 131mm2, 512K L2

Second Generation Pentium 4 Architecture

The first generation Pentium 4 was reasonably competitive with the contemporary Opterons. On the 130nm process, the Pentium 4 at 3.0GHz had broadly comparable performance to Opteron at 2.0GHz. Depending on the nature of the application, Pentium 4 had an advantage on some and Opteron on others. The Intel strategy for the second generation Pentium 4 architecture (see The Microarchitecture of the IntelŪ PentiumŪ 4 Processor on 90nm Technology ) codename Prescott on 90nm in March 2004 was to achieve even more extraordinarily high clock rates, hence the deeper pipelining to 31 stages.

Unfortunately for Intel, the leakage current for off-state transistor in the 90nm process was much higher the anticipated, so the Prescott core could not clock any where near as high as it was designed, within the 130W envelope that capped the amount heat that could be removed from a medium sized die (112 square mm) with air-cooling. At 90nm, Pentium 4 reached 3.8GHz (3.66GHz in MP server variants, 3.33GHz with 8M L3 cache) compared with 2.8-3.0GHz for Opteron. There are indications that the second generation Pentium 4 architecture was targeted to reach 5-6GHz at 90nm and 9GHz on the 65nm process.

The Prescott Pentium 4 were 64-bit microprocessors. 2004 Q1, 125M transistors, 112mm2.

Prescott, 2004 Feb, 112mm2, 1M L2

In 2005, a Prescott with 2M L2 came out.

Prescott, 2005, 135mm2, 2M L2

Cedar Mill 65nm, Q1 2006

Cedar Mill
Cedar Mill, 2006 Jan, 65nm, 81mm2, 2M L2

Potomac was the 90nm server server with 8M L3.

A brief note on comparing Intel and AMD processor frequencies: Intel tends to introduce a processor line with a range of frequencies, and then sometimes provide one or two higher frequencies later, but the main focus is to launch the next generation. AMD may incremental frequencies throughout the product life.

Intel Hyper-Threading

Note: this topic moved to: Hyper-Threading,