Dual-core Intel Conroe processors
Introduction
Three years ago, AMD released a line of processors with the
new A64 architecture and immediately won a technology advantage.
Athlon64 processors ran at much lower clock speeds than Intel Pentium4
but demonstrated high higher performance. That was especially seen in
gaming applications, i.e. in the field which is most common for
home-based users. The advantage in speed was won due to the shorter
pipeline as well as the integrated memory controller. Intel was
struggling to the very best of its power continuously raising the clock
speeds of it processors. But ... stopped the race having finally not
achieved the 4 GHz threshold. Further rise in the clock speeds was
simply impossible: the heat emission went beyond all the reasonable
boundaries.
To be fair, we should note that Intel's latest processors
produced following the 65 nm process technology smoothed the problem of
power consumption a bit. But Intel failed to grab the performance
crown. Therefore, AMD was gradually expanding its market share, and in
mere three years it overcame the ~25% barrier. In fact, that is the
maximum possible market share for AMD because of the lack of production
capacities.
Of course, Intel was strongly against this situation. And some
time ago there appeared first rumors on the forthcoming new processor
architecture. There also appeared first specimens - I mean mobile CPUs
Pentium-M on the Dothan core. Manufactured following the
90-nm process technology and running at ~ 2.5 GHz clock speeds, these
processors showed a very high operating speed comparable to to that of
top-end desktop AMD and Intel processors. Pentium-M proved so highly
attractive that some companies prepared matching solutions for desktop
systems.
A bit later though, there appeared first information on
processors built on the Intel Core 2 Duo architecture, which made the
interest to Pentium-M gradually fade. Roughly speaking, the Core 2 Duo
architecture is a logical evolution of the Pentium Pro architecture
with the use of all Intel's technologies and developments. In
particular, the new processors offer a rather short pipeline (14
stages) and are able decoding and executing up to instructions per
cycle. For more detail of the Core 2 Duo architecture, read our previous
materials. Today, we are focusing on the practical aspects of
operating the new processors.
In August 2006 onwards, the following models start appearing
in the retail:
| Processor |
Core |
Clock speed, GHz |
Multiplier |
Bus speed, MHz |
L2 cache size, MB |
Typical heat emission, W |
Price, $ |
| Core 2 Extreme X6800 |
Conroe |
2,93 |
11 |
1066 |
4 |
75 |
999 |
| Core 2 Duo E6700 |
Conroe |
2,67 |
10 |
1066 |
4 |
65 |
530 |
| Core 2 Duo E6600 |
Conroe |
2,4 |
9 |
1066 |
4 |
65 |
316 |
| Core 2 Duo E6400 |
Allendale |
2,13 |
8 |
1066 |
2 |
65 |
224 |
| Core 2 Duo E6300 |
Allendale |
1,86 |
7 |
1066 |
2 |
65 |
183 |
| Core 2 Duo E4300 * |
Allendale |
1,80 |
9 |
800 |
2 |
65 |
?? |
* - Core 2 Duo E4300 will appear in the retail even in Q'1 of
2007.
Therefore, Intel has presented two cores of the Core 2 Duo
architecture. These are Conroe and Allendale which differ in only the
L2 cache size: 4 MB and 2 MB, respectively. Of note is that the L2
cache is shared, i.e each core is able fetching data from the whole
cache size. We also mention the processor core Millvile which will have
only one core. It is quite probable that value-sector processors will
be released on its based (I presume that will no happen earlier than
2007).
Visually, processors built on the Conroe and Allendale cores
do not differ much from other LGA775 processors. In particular, the
front side is hidden by a heat-spreader and fully coincides with other
processors except the marking.
Just guess which of these is Conroe
On the reverse side, we can see some slight changes in the
positioning of capacitors.
The CPU-Z utility displays the following information:
Just note the CPU stepping: The test specimen is of stepping
B1. In fact, all the engineering samples and rare processors of the
very first batches have had steppings B0 and B1. But all the processors
to be sent to the official sales have stepping B2.
Now let's look into other issues. Which of the listed
processors should we buy? The answer is simple - the one you have
enough money for. Another important question - which motherboard to
choose? At that, there are more fine points. First, we should keep it
in mind that the vast majority of LGA775 motherboards are incompatible
to Core 2 Duo processors. The thing is, to support Intel's latest
processors the power supply module of the motherboard should conform to
the VRM 11 specifications. There are few of such motherboards: a couple
of motherboards on the base of i975P (Intel D975XBX Bad Axe) and ASUS
P5W-DH Deluxe), as well as a few boards on the P965 chipset.
Once the P965 has been released, the number of motherboards on its base
will be increasing (and they will all be compatible to the Core 2 Duo).
It now makes sense to think which processor to take with
overclocking kept in mind. Clearly, you should buy the cheapest, i.e.
Core 2 Duo E6300 built on the Allendale core. It is also important to
note that although the L2 cache size in Allendale is twice as small as
in the Conroe core, the performance difference at a similar clock speed
is within 2% (in some applications - up to 5-6%). Therefore, you don't
have to worry about the small cache. But what you really have to take
care of seriously is the multiplier which is = 7 in the model E6300.
That means, to achieve the technology limit 3.5 GHz (provided there is
air-driven cooling), we should increase the FSB speed to 500 MHz. That
is a really impressive speed: for example, the FSB limit for Asus
P5W-DH Deluxe is 450 MHz. Besides, for a stable operation at such
frequencies there must be a feature for raising voltage on the
chipset's north bridge. Therefore, the selection of a Core 2 Duo
motherboard has to be effected really thoroughly. Quite possibly, it's
better to spend a bit more to but a more expensive CPU with greater
multiplier. In other words, we add 40$ and buy E6400 with the
multiplier 8. As a result, to reach 3.5 GHz we should raise the FSB to
437 MHz, which is quite feasible! Therefore, potentially it is just the
E6400 model that will be the overclocker's choice until the end of
2006. To be more precise, until the release of E4300 which runs at 1.8
GHz with the system bus speed 800 MHz (QPB). It's easy to calculate
that the multiplier of the CPU is set to 9, which substantially
facilitates overclocking. Again, this model will be the cheapest of all
the Core 2 Duo processors.
Once we are talking about the overclocking issues, let's
conduct a small research "Overclocking and heat emission on the Conroe
core".
Overclocking and heat emission
We note straight that Conroe and Allendale processors running
in the nominal mode have a very low, to modern standards, heat
emission. In particular, the lower CPU E6300 at 1.86 GHz has a typical
heat emission = 65 W. Of major part in that is the very thin (65 nm)
process technology as well as the relatively low supply voltage.
With the Enhanced Intel SpeedStep enabled, the heat emission
drops to 22 W. At the same time, the multiplier drops to 6, and the
Vcore voltage reduces. Other processors also support this technology
which allows reducing the multiplier to 6. So, for most users a boxed
cooler would suffice. By the way, the new Conroe core contains 291 mln
transistors, with its area being 144 sq.mm.
As regards overclocking using air-driven cooling, then with
the Gigabyte G-Power cooler we were able to attain 3.46 GHz clock speed
with a minor rise of the Vcore. At the same time, the CPU temperature
even when both cores are fully loaded, did not exceed 54°
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