Pentium D is a series of microprocessors introduced by INTEL at the Spring
2005 Intel Developer Forum. A Pentium D package contains two Pentium 4 Prescott dies,
unlike other multicore processors which place both cores on a single die.
The Pentium D was the first announced multicore CPU (along with its more expensive
twin, the Pentium Extreme Edition) from any manufacturer intended for desktop
computers. Intel underscored the significance of this introduction by predicting that by
the end of 2006, over 70% of its shipping desktop CPUs would be multicore. Analysts
have speculated that the clock rate race between Intel and AMD is largely over, with no
more exponential gains in clock rate looking likely. Instead, as long as Moore's Law
holds up, it is expected that the increasing numbers of transistors that chip-makers can
incorporate into their CPUs will be used to increase CPU throughput in other ways, such
as by adding cores, as the Pentium D does.
With the announcement of the Intel Core brand for their future processors, the
Pentium D is the final processor to carry the Pentium brand name that has been at the
forefront of Intel's products since 1993.
It has always been a frequent question -- "Will I benefit from multiple
processors?" With the growing popularity of dual core processors, the topic is more
important than ever! Will multiple processors or a dual core processor be beneficial to
you, and what are the differences between them? These are the questions this article will
attempt to lay to rest.
A major question for some people getting ready to buy a high-end system is
whether they want or need to have two processors available to them. For anyone doing
video editing, multi-threaded applications, or a lot of multitasking the answer is a very
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clear 'yes'. Then the question becomes whether two separate processors (as in a dual
Xeon or Opteron system) is the way to go, or whether a single dual-core CPU (like a
Pentium D or Athlon64 X2) will do just as well. Dual CPU vs dual core -- which is
better?!
Intel released the first Pentium D products (codenamed "Smithfield") on May 26,
2005, with clock speeds of 2.8, 3.0, and 3.2 GHz. The chips carried model numbers of
820, 830 and 840 respectively. An 805, clocked at 2.66 GHz with a 533 MT/s bus,
appeared in early 2006.
Smithfield is made on a 90nm process with 1MiB of L2 cache per core. The
Smithfield Pentium D does not support Hyper-Threading, although similar Pentium
Extreme Edition counterparts do. Smithfield does not support VT, Intel's virtualization
feature formerly called Vander pool.
The Pentium D processor supports Intel's EM64T technology, the XD Bit and like
most current Pentium 4s, uses the LGA775 form factor on an 800 MT/s bus. The only
motherboards guaranteed to work with the Pentium D (and Extreme Edition) are those
based on the 945, 955 and 975 series of chipsets, as well as the enforce 4 SLI Intel
Edition. The Pentium D 820 won't 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 making Xeon motherboards with the chipsets, as
happened with the 875P). The 865 and 875 series chipsets do have multiprocessor
support, so motherboards based on these chipsets may be Pentium D compatible, so long
as the manufacturer provides an appropriate BIOS update.
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 — such as most 3D rendering programs and video encoders — and in
heavy multitasking situations where the PC user is running several CPU-heavy
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applications, and each core can handle a different application. Most business applications
and games as of 2005 only use 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, BSDfamily,
or Microsoft Windows operating systems.
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 it 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.
The newest generation of Pentium D processors are based on the Presler core, a
pairing of "Cedar Mill" cores. Even though Presler is a single package, that package has
two dies in it, enhancing manufacturing yields of the processor over a single die
approach. Presler can be supported by the same chipsets as Smithfield. It is produced
using the 65 nm technology. Presler communicates with the system with an 800 MT/s
FSB (while the Pentium Extreme Edition 955 and 965 use a 1066 MT/s FSB), and the
two cores communicate using the FSB, just as Smithfield does. It also includes VT
(Virtualization Technology, aka Vander pool), EM64T, XD bit and EIST (Enhanced Intel
SpeedStep Technology)¹. It was released in the 1st quarter of 2006. Models include 920,
930, 940, 950 and 960 (2.8, 3.0, 3.2, 3.4 and 3.6 GHz).
¹ - First batch of Presler CPUs (revision B1) have EIST feature turned off by
microcode update because of stability issues. This affects only idle power consumption
and thermal dissipation. Chips with working EIST will start shipping in Q2 2006. They
will have different S-Spec number which can be found in Intel errata documentation, or
here.
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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. To use a crude analogy, one can 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.
INTEL DUAL PROCESSOR USE AS SERVER: Dual-core processors deliver
a quantum leap in processing capacity without a comparable increase in power
consumption, enabling businesses to grow their computing solutions more efficiently and
at reduced cost. Future Intel® processors will extend these advantages by integrating
more cores per processor, which is projected to increase server performance.
As this transition gains momentum, Intel is uniquely positioned to deliver the
solutions and resources businesses need to maximize the value of migration, while
reducing their associated costs and risks.
Above
figure shows the Intel dual core processor. There are two cores in it. Core 0 contains 32
bit and core 1 contains 32 bit
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