Pentium D

Pentium D

File:Pentium d.jpg
General information
Launched	2005
Discontinued	2007
Common manufacturer	Intel
Performance
Max. CPU clock rate	2.66 GHz to 3.73 GHz
FSB speeds	533 MT/s to 800 MT/s
Architecture and classification
Technology node	0.09 to 0.065
Microarchitecture	NetBurst
Instruction set	MMX, SSE, SSE2, SSE3, x86-64
Physical specifications
Socket	LGA 775
Products, models, variants
Core names	Smithfield Presler

Pentium D logo as of 2006.

Pentium D is a dual core 64-bit NetBurst microarchitecture processor introduced by Intel May 25th, 2005 with production ceased March 9th, 2007. The first Pentium Ds, the 8xx-series codenamed Smithfield, comprised of two single-core dice in one package (termed a Multi-Chip Module). Nine months later Intel introduced its successor, the 9xx-series codenamed Presler , consisted of two processing cores on one die.

By 2005, the clock speed race between Intel and AMD was largely over due to thermal and power barriers encountered at high clock speeds. Multi-core CPUs offered a solution to this problem and led to the new multi-core race. The additional processing core in Pentium D CPUs offer a potential increase in performance without drastically increasing power consumption in the process.

As with a multiprocessor PC, the Pentium D provides significant performance improvement only with applications that have been written specifically for multiple CPUs or cores. Examples include most 3D rendering programs and video encoders. Most business applications and games as of 2006 use only a single thread, so for these applications running alone the Pentium D will deliver largely the same performance as an older Pentium 4 running at the same clock rate. However, applications rarely run alone on PCs running Linux, BSD-family, or Microsoft Windows operating systems. In multitasking situations, like virus scanner running in the background, where the PC user is running several CPU-intensive applications each core can handle a different application, improving performance.

Smithfield

Smithfield was the first x86 dual-core microprocessor intended for desktop computers. Intel first launched Smithfield on April 16th, 2005, in the form of the 3.2 GHz Hyperthreading-enabled Pentium Extreme Edition 840. On May 26th, 2005 Intel launched the mainstream Pentium D processor lineup with initial clock speeds of 2.8, 3.0, and 3.2 GHz with model numbers of 820, 830, and 840 respectively. In March 2006 Intel launched the last smithfield processor, the entry-level Pentium D 805, clocked at 2.66 GHz with a 533 MT/s bus. The relatively cheap 805 was found to be highly capable of overclocking; running the processor in a stable state at over 3.5 GHz was easily possible with standard air cooling. Running it at over 4 GHz was possible with water cooling, and at this stage the 805 outperformed top-of-the-line processors (May 2006) from both major CPU manufacturers (the AMD Athlon 64 FX-60 and Intel Pentium Extreme Edition 965) in many benchmarks.

The Thermal Design Power for models 805 and 820 is rated at 95 watts. All other models are rated at 130 watts; 37% additional power.

Smithfield is made of two 90-nm process Pentium 4 Prescott cores put together in a single die with 1 MiB of Level 2 (L2) cache per core. While Smithfield is capable of hyperthreading technology, this feature has been disabled on all Pentium D 8xx CPUs, with the Pentium Extreme Edition 840 having the distinction of being the only Smithfield CPU to have hyperthreading enabled. Smithfield does not support VT, Intel's virtualization feature formerly called Vanderpool.

All Pentium D processors support Intel 64 (EM64T), XD Bit, and are manufactured for LGA775 form factor. The only motherboards guaranteed to work with the Pentium D (and Extreme Edition) are those based on the 945, 955, and 975 series of Intel chipsets, as well as the nForce 4 SLI Intel Edition and ATI Radeon Xpress. The Pentium D 820 will not work with the nForce 4 SLI Intel Edition due to some power design issues, though they were rectified for the X16 version of the chipset. Motherboards based on the 915 and 925 series of chipsets will not work at all, as the chipsets do not have support for more than one processor core (a result of Intel trying to prevent motherboard manufacturers from making Xeon motherboards with the chipsets, as happened with the 875P). The 865 and 875 series chipsets do have multiprocessor support. Motherboards based on those chipsets may be Pentium D compatible so long as the manufacturer provides an appropriate BIOS update.

After a week of confusion following the processor's launch, Intel officially denied a report in Computerworld Today Australia that the Pentium D includes "secret" digital rights management features in hardware that could be utilized by Microsoft Windows and other operating systems, but was not publicly disclosed. While Intel admitted that there were some DRM technologies in the 945 and 955 series of chipsets it stated that the extent of the technologies was exaggerated, and that the technologies in question had been present in Intel's chipsets since the 875P.

Presler

The newest generation of Pentium D processors are based on the Presler core, pairing of "Cedar Mill" dies identified by the product code 80553. Even though Presler is a single package, that package has two dies in it that double the amount that the processor can perform. This method enhances manufacturing yields of the processor over a single die approach. Presler can be supported by the same chip sets as Smithfield. It is produced using 65 nm technology similar to the Core Duo. Presler communicates with the system using an 800 MT/s FSB, and the two cores communicate using the FSB just as Smithfield does. It also includes VT (Virtualization Technology, aka Vanderpool, although this is only on the 9x0 models, not the 9x5 models), Intel 64, XD bit and EIST (Enhanced Intel SpeedStep® Technology)¹. It was released in the 1st quarter of 2006. All models have a 2x2 MiB Level 2 cache. Models include 915, 920, 925, 930, 935, 940, 945, 950, 955, 960 and 965 (2.8, 2.8, 3.0, 3,0, 3.2, 3.2, 3.4, 3.4, 3.46, 3.6 and 3.73 GHz clock frequency).

The Thermal Design Power for models 915, 920, 925, 930, 940, 950 stepping C1, and 915, 925, 935, 945, 950, 960 stepping D0 are rated at 95 watts. All other models are rated at 130 watts; 37% additional power.

¹ - The first batch of Presler processors (revision B1) have the EIST feature turned off by microcode update because of stability issues. This affects only idle power consumption and thermal dissipation. Chips with working EIST started shipping in Q2 2006. They had a different S-Spec number which can be found in Intel errata documentation, or here

Pentium Extreme Edition

Smithfield

Original Pentium Extreme Edition logo.

Pentium Extreme Edition logo as of 2006.

Pentium Extreme Edition was introduced at the Spring 2005 Intel Developers Forum, not to be confused with the "Pentium 4 Extreme Edition" (an earlier, single-core processor occupying the same niche). The processor is based on the dual core Pentium D featuring Intel's Smithfield and later Presler cores, but it has Hyperthreading enabled, thus any operating system will see 4 logical processors (2 physical x 2 virtual cores). It also has an unlocked multiplier to allow for overclocking. It was initially released as Intel Pentium Extreme Edition 840 at 3.20 GHz, in early 2005, at a price point of $999.99 (OEM) or $1,200 (Retail). The only chipsets that will work with the Extreme Edition 840 are Intel's 955X and NVIDIA's nForce4 SLI Intel Edition or ATi Radeon Xpress 200. Attempting to use an Extreme Edition with an Intel 945-series chipset will disable Hyperthreading, effectively turning the processor into a Pentium D.

Presler

The Pentium Extreme Edition based on the Presler core was introduced as the 955, at 3.46 GHz, and uses a 1066 MT/s FSB compared to the 800MT/s on the non-extreme edition. A second version, the 965 at 3.73 GHz followed in March 2006. Many overclockers, however, have been able to overclock the core to 4.26 GHz using air cooling simply by raising the unlocked CPU multiplier.

The Presler Extreme Edition will only run combined with the Intel 975X chipset. i975X features the ICH7R southbridge and accepts all LGA775 Pentium 4, Pentium D and Pentium Extreme Edition processors.

Successor

Main article: Intel Core 2

The Pentium D brand was succeeded on July 27, 2006 by the Core 2 branded line of microprocessors with the Core architecture released as dual- and quad-core CPUs branded Duo, Quad, and Extreme.

Implementation

In a single-processor scenario, the CPU-to-north bridge link is point-to-point and the only real requirement is that it is fast enough to keep the CPU fed with data from memory.

When assessing the Pentium D, it is important to note that it is essentially two CPUs in the same package and that it will face the same bus contention issues as a pair of Xeons prior to the Dual Independent Bus architecture introduced with the Dual-Core Dempsey Xeons. To use a crude analogy one could say that instead of using a single cable between CPU and north bridge, one must use a Y-splitter. Leaving aside advanced issues such as cache coherency, each core can only use half of the 800 MT/s FSB when under heavy load.

See also

• List of Intel Pentium D microprocessors

External links

• Intel Pentium D Official Website
• Pentium D 800 and 900 Series Review
• Intel Pentium D technical specifications