Intel’s 15 Most Unforgettable x86 CPUs-Part 2

Pentium M: Laptops Flex Their Muscles

In 2003 the market for portable PCs was booming and Intel had only two processors for them: the aging Pentium III Tualatin and the Pentium 4, whose high power consumption made it unsuitable. But a savior was to arrive from Israel: the Banias (alias Pentium M). This processor, based on the P6 architecture (the same as the Pentium Pro) had high performance and low power consumption. It even beat the Pentium 4, while consuming a lot less power. This was the processor used in the Centrino platform and it was quickly followed (in 2004) by the (faster) Dothan model. The Pentium M left its mark on the world of mobility, and the Stealey (A100) still uses the Dothan architecture (with lower frequencies and TDP).

Intel Pentium M

Code name	Banias	Dothan
Date released	2003	2004
Architecture	32 bits	32 bits
Data bus	64 bits	64 bits
Address bus	32 bits	32 bits
Maximum memory	4 GB	4 GB
L1 cache	32 KB + 32 KB	32 KB + 32 KB
L2 cache	1,024 KB	2,048 KB
Clock frequency	0.9–1.7 GHz	1–2.13 GHz
FSB	400 MHz	400, 533 MHz
SIMD	MMX, SSE, SSE2	MMX, SSE, SSE2
SMT/SMP	no	no
Fabrication process	130 nm	90 nm
Number of transistors	77 million	140 million
Power consumption	9-30 W	6-35 W
Voltage	0.9–1.5 V	0.9–1.4 V
Die surface area	82 mm²	87 mm²
Connector	Socket 479	Socket 479

As with the Pentium 4, the FSB actually operated at a quarter of the nominal frequency (QDR). The connector used, the Socket 479, actually had 478 pins, but they were arranged differently from the Pentium 4 Socket 478 (though adapters were made).

Pentium 4 Gets 64-bit And Another Core

In 2005, Intel improved its Pentium 4 twice. First, with the Prescott-2M, and then with Smithfield. The former was a 64-bit processor, based on the Prescott design, and the latter was a dual-core processor. They are fairly similar and have the same problems as other Pentium 4s: low instructions per cycle (IPC) throughput and difficulty in increasing the clock frequency due to current losses. These two processors, intended to limit losses while awaiting the Core 2 Duo, are not among Intel’s most highly regarded. And while the Pentium D (the commercial name of the Smithfield) does have two cores, in reality it’s an assembly of two Prescott dies in the same package.

Intel Pentium 4

Code name	Prescott-2M	Smithfield
Date released	2005	2005
Architecture	64 bits	64 bits
Data bus	64 bits	64 bits
Address bus	64 (actual 36) bits	64 (actual 36) bits
Maximum memory	64 GB	64 GB
L1 cache	16 KB + 12 Kµops	2 x 16 KB + 12 Kµops
L2 cache	2,048 KB	2 x 1,024 KB
Clock frequency	3–3.6 GHz	2.8–3.2 GHz
FSB	800 MHz	800 MHz
SIMD	MMX, SSE, SSE2, SSE3	MMX, SSE, SSE2, SSE3
SMT/SMP	Hyper-Threading	dual cores (Hyper-Threading on certain models)
Fabrication process	90 nm	90 nm
Number of transistors	169 million	230 million
TDP	84-115 W	95-130 W
Voltage	1.2 V	1.2 V
Die surface area	135 mm²	206 mm²
Connector	LGA775	LGA775

An interesting point is that whereas the Pentium 4 processors intended for the consumer market did not use the PAE technology (which enables 36-bit, as opposed to 32-bit memory management) and were therefore limited to 4 GB of RAM, these models can go beyond that limit. In practice, the address bus is still limited to 36 bits (40 bits on the Xeon), but PAE (management in 4 GB pages) is now ancient history—a 64-bit program is capable of making full use of the available memory.

Hyper-Threading, an Intel SMT technology, was available on certain models (Xeon and Extreme Edition). Finally, a 65 nm version (the 9×0 series) of the Pentium 4 was released later, but made no major improvements.

The First Mobile Dual-Core

In 2006, Intel announced the Core Duo. The first dual-core processor for portable PCs boasted excellent performance—much better than the Pentium 4. It was also one of the first x86 processors to be truly dual-core. The cache, for example, is shared (whereas the Pentium D was more like an assembly of two processors in the same package). This processor was part of the Centrino Duo platform and was a huge success. The only drawback was that it was still a 32-bit processor, unlike the Pentium 4.

Intel Core Duo

Code name	Yonah
Date released	2006
Architecture	32 bits
Data bus	64 bits
Address bus	32 bits
Maximum memory	4 GB
L1 cache	32 KB + 32 KB
L2 cache	2,048 KB shared
Clock frequency	1.06–2.33 GHz
FSB	667 MHz
SIMD	MMX, SSE, SSE2, SSE3
SMT/SMP	Dual core
Fabrication process	65 nm
Number of transistors	151 million
TDP	9-31 W
Voltage	0.9–1.3 V
Die surface area	91 mm²
Connector	Socket 479

A Core Solo version with one core was also made available, and the low-power-consumption versions used a 533 MHz bus (133 MHz QDR) instead of 667 MHz. This processor was used in servers (code name Sossaman), which was a first for a processor originally intended for the mobile world. Note that this processor didn’t officially use the Core architecture of the Core 2 Duo, and it was quickly replaced by the Core 2 Duo (Merom) in portable PCs. Also, the Yonah’s Socket 479 is different from the Socket 479 of other Pentium M processors.

Today’s Hotness: The Core 2 Duo

In 2006, Intel released a processor that quickly became a best-seller: the Core 2 Duo. Derived from work done on the Pentium M, this processor uses a new Core architecture. Before, Intel had two lines of processors—the Pentium 4 for desktops, Pentium M for mobiles, and both lines for servers. In contrast, Intel now has a single micro-architecture on which all of its product lines draw. The 64-bit Core 2 Duo is represented from the low end to the high end, for desktop computers, portables and servers.

There are many versions of the architecture, resulting in configurations with a different number of cores (one to four, yielding everything from Solos to Quads), cache memory (512 KB to 12 MB), and the FSB (between 400 and 1600 MHz). The model shown here is the original Core 2 Duo, but faster versions (at 45 nm) exist.

Intel Core 2 Duo

Code name	Conroe
Date released	2006
Architecture	64 bits
Data bus	64 bits
Address bus	64 (actual 36) bits
Maximum memory	64 GB
L1 cache	32 KB + 32 KB
L2 cache	2,048 KB shared
Clock frequency	1.8-3 GHz
FSB	800-1066-1333 MHz
SIMD	MMX, SSE, SSE2, SSE3, SSSE3
SMT/SMP	Dual core
Fabrication process	65 nm
Number of transistors	291 million
TDP	65 W
Voltage	1.5 V
Die surface area	143 mm²
Connector	LGA 775

The mobile versions (Merom) are basically identical (but not as fast, with a slower FSB) whereas the Extreme Edition versions are faster. The Core 2 Duo also exists in a four-core version, which was, in fact, two Conroes in the same package. The 45 nm version of the Core 2 Duo (Penryn) has a larger cache and generates less heat, but is still fundamentally similar to this model.

The Future: Nehalem, Atom, Etc.

Obviously, this is only the first part of a series of articles. The second part, on AMD processors, will follow (along with a piece on AMD’s ATI graphics cards). But the story of the Intel x86 processors doesn’t end with the Core 2 Duo, and obviously other models are planned for the future. Nehalem and Atom are also x86 processors. And a little bird tells us that Intel’s upcoming entry into the graphics market, Larrabee, is also based on a number of x86 cores.