Quad-core Intel Kentsfield processors
Introduction
First of all, a brief contents of the review for those readers
who immediately move to the performance diagrams. So, Intel has
released a 4-core processor which appears to be two Conroe cores
packaged in a single housing. Therefore, in programs that offer
optimization for multithreading this processor can provide a 3-fold
performance boost. But in programs without such optimization (e.g., 99%
of games), its speed will be on par with that of Conroe.
Now let's take a closer look at the new processor. Above all,
it is called Core 2 Extreme QX6700, has a LGA775 socket and in theory
it should be compatible to a wide range of motherboards. Although
according to Intel's official information this processor is able
running on only i975X-based motherboards, we are sure that soon the
leading manufacturers will announce support for QX6700 by motherboards
based on the P965 and the latest versions of nForce Intel Edition. It
is quite possible that it will be supported by other chipsets, since
QX6700 requires a power supply module meeting the VRM 11
specifications, as well as support by the BIOS.
What sense is behind the starting migration of desktop
computers towards quad-core processors? The major idea is in the more
efficient handling of resource-intensive multimedia applications,
including that of entertainment character. However, the character of
providing a performance boost implies the need for expansion of
software support for multitasking and multithreading, so the trend is
linked to not only the hardware part, but it is just at the very start.
Since the innovation of the Intel Core micro architecture is
already described at length in our review Evolution
of the multi-core Intel Core processor architecture: Conroe,
Kentsfield.., it makes no sense repeating on that subject
herein. The most important thing which we would like to note is: the
key capabilities of the new-generation architecture implemented in the
formerly described technologies - Intel Wide Dynamic Execution, Intel
Intelligent Power Capability, Intel Advanced Smart Cache, Intel
Advanced Digital Media Boost, and Intel Smart Memory Access - are still
topical for 4-core CPU Core 2 Extreme QX6700 in the same way as it is
for its 2-core brethren. The only difference is in that now the new
Intel Core architecture is implemented in four independent cores on a
single substrate, with 8 MB L2 cache (4 MB per each pair of cores),
which provides support for four independent physical threads and in
theory allows to achieve an additional performance boost (with the
adequate operation of the platform's software part).
In our tests, we used the motherboards Intel D975XBX2 ("Bad
Axe") and ASUS P5W64 WS Pro (both on the i975X chipset).
Therefore, with support for the QX6700 processor by the
motherboard, upgrade is performed only through replacement of the
processor. The thing is that the computer industry is fully ready for
the emergence of 4-core processors. In practice, this is expressed in a
wide assortment of of powerful coolers which are able dissipating
130-150 W, as well as a great number of powerful (>500 W) power
supply units.
Remarkably, the emergence of QX6700 has happened merely three
months after the emergence of the Conroe Allendale core. Such a high
speed of development can be explained by that these processors were
developed almost simultaneously. Already at the initial stages of
development, the specifications for Conroe were complemented with the
requirement of compatibility to the 2-core configuration. In other
words, placement of two Conroe cores into a single processor (each core
also dual-core) allows producing a 4-core processor. And the small
power consumption of Conroe allows fitting within the 150 W limit for
the 4-core configuration (official data on TDP for QX6700 tell of 130 W
of power consumption).
By the way, this approach to development of dual-core
processors continues Intel's tradition. In precisely the same way, the
Smithfield and Presler processors were manufactured. By the way, the
latter has two Cedar Mill cores, is manufactured following the 65-nm
process technology and so far has been the only processor which is able
executing 4 command threads simultaneously. The thing is that both the
integrated cores offered support for the HyperThreading technology.
Therefore, it would be especially interesting to compare performance of
Presler versus that of Core 2 Extreme QX6700.
In the end, the new processor has been codenamed as Kentsfield
and various diagnostic utilities use just that.
As we see, the clock speed of QX6700 equals 2.66 GHz, the
system bus speed is 266 MHz (1066 MHz QPB) and thus the multiplier =
10. The L2 cache size is 8 MB (2 x 4 MB), and the nominal supply
voltage may vary within 1.25 V to 1.35 V depending on the stepping.
Visually, the new processor makes little difference from its
LGA775 brethren. The front side of has no marking at all (except the
marking), and on the reverse side the Kentsfield can be recognized by
the configuration of capacitors:
From left to right: Kentsfield, Conroe, Presler, Gallatin,
and Prescott 2M
Close view:
Let's digress from the processor for some time and consider
Intel's general approach to increasing the performance of its
processors. Having burnt its fingers on the NetBurst architecture that
called for a serious increase in the clock speed, Intel changed its
approach and released a new-generation architecture - the Core 2 Duo.
The latter provides a revolutionary leap in performance under a rather
small power consumption. At the same time, as numerous experiments with
overclocking showed, the margin for raising the clock speeds is simply
tremendous (up to 3.4-3.6 GHz). The latter factor would have let easily
rubber-stamp all the new versions of processors for another two years
(right before migration to the 45-nm process technology). However, the
general trends of computer industry require parallel computations.
Therefore, Intel's major strategic goal is the development of
multi-core processors.
To date, the attitude to 2- (and more) core processors is not
unanimous. On the one hand, there is still very little optimized
software, and such programs can be found only among professional
software. That is, for the home user multicore processors seem to be
useless. But on the other hand, the dual-core processor provides more
comfortable operation with Windows XP (and other operating systems).
But the "comfort" is a subjective thing and can't be expressed
numerically. But in my personal experience this "comfort" is tangible
enough and allows to recommend just dual-core processors.
Even the dual-core Celeron allows to feel the
difference in the comfort of work! By a Celeron I mean cheap Smithfield
processors (e.g. again the same dual-core Pentium 805). And the
buyer should not be confused by its name Pentium: the performance of
Conroe processors is so high that it immediately moves all the other
LGA775 processors to the category of low- and middle-end products.
So, in the nearest future we can expect an increase in the
number of cores on a single processor. I think this won't happen
earlier than 2008 when Intel moves to a new (45 nm) process technology
and demonstrates a new processor architecture. I believe by that time
we can expect the emergence of first 8-core processors. Therefore, the
rise of performance occurs in the following two directions: increase of
the architectural performance (i.e of a single core), and increase in
the number of cores on a single processor.
I think that time will be the epoch of prosperity for
multi-core processors. Optimization for multi-threading will become a
mandatory requirement for software development (probably such
optimization will be integrated at the level of development tools), and
single-core processors will simply vanish away from retail stores.
Besides, in 2007 the new operating system MS Vista is released and
therefore all the most recent software development is biased towards
just this system. And quite possibly that we'll get the first fruits of
multi-core system advantages in a matter of a few weeks.
As I already stated, to date there is very little optimized
software, and it can be met most often among the 3D graphic processing
software, as well as software for encoding streamed data (video and
audio), data compression (archivers), and image processing. So, we'll
start testing the CPU Core 2 Extreme QX6700 just with these
applications. But before we proceed, we consider the overclocking
capability of the new processor.
Overclocking and heat emission
Since Kentsfield is made up of two Conroe cores, then it is
clear that the potentials for increase in the clock speed will not
exceed the limits of the Conroe core. However, placing two cores on a
single processor results in that the maximum possible clock speed is
restricted by the potentials of the "weakest" core. On the other hand,
to manufacture Kentsfield cores, Intel selects only the best-of-breed
cores, which tells in favor of overclocking. In general, we can expect
that the technology limit is at about 3.5 GHz.
And it proved to be the way we expected: the maximum stable
clock speed of our CPU specimen proved to be 3.45-3.5 GHz with air
cooling (using the Gigabyte G-Power cooler). At the same time, we
should note that the processor successfully started at 3.66 GHz, but
stable operation was impossible because of a too high heat emission.
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