iXBT Labs - Computer Hardware in Detail






Intel Core 2 Duo (Conroe) E6400 and E6700:
A Start to Be Remembered

June 15, 2006

"At last!!!" (Instead of Introduction)

Rumours about wondrous performance of the new desktop processors from Intel have been circulating for a long time already. From time to time they were confirmed by various express tests. But the structure of those tests and their numbers did not allow to evaluate how cool the new processors were in any article we had read. Fortunately, the situation has changed now that we got hold of a system with the long-awaited engineering sample of the new desktop CPU from Intel, based on Conroe core — Core 2 Duo E6400 (2.13 GHz). Indeed, our processor was a real engineering sample, some intermediate modification at that: its clock is like in the production-line E6400, but its L2 Cache is twice as large (judging from some grapevine about specifications of production-line processors.) Besides, the motherboard of our system (we got a ready system, actually) was based not on the top chipset — i965. Fortunately, we got another combo just in a couple of days: Production-line Intel Core 2 Duo E6700 (2.66 GHz) and Intel D975XBX motherboard with an updated BIOS version that can work with this processor.

So when you browse the results, you should take into account the following: Core 2 Duo E6400 is represented by an engineering sample, which characteristics may differ a little from the release model, and works with an i965-based motherboard. Core 2 Duo E6700 is represented by a release model and works with an i975X-based motherboard. Of course, we could have waited until we got all production-line samples and published an "ideal" article. But as nobody offered us new Intel processors on Conroe core, we decided not to be so fastidious. Quick-look article seemed more important than conceptual completeness.

Brief Characteristics of
Intel Core 2 Duo Processors

The architecture of Intel Core 2, represented by the desktop core Conroe, has grown from the mobile core Yonah. Which in its turn stems from the ideas of Pentium M (Banias and Dothan). What concerns the latter, it has been noted many times that they are direct descendants of the 6-gen core of Intel processors (P6), which had been designed prior to Pentium Pro and had lived to Pentium III. Thus, on one hand, Core 2 is a step back, as it sort of cancels many architectural solutions that appeared in processor cores of the later generations (the famous Intel NetBurst architecture of the seventh generation). On the other hand, we cannot say that Core 2 is the direct heir to Intel P6 because of too many modifications. The new core has been altered beyond recognition :).

The key differences of the new architecture from the closest parent — Intel Core Duo (Yonah) come down to the following:

  • Improved decoder, expanded to 4 decoders of x86 macro-ops (3 in the closest counterparts, Intel Pentium M / Core Duo).
  • The execution speed of 128-bit SIMD instructions is one instruction per cycle in each execution unit (twice as fast as Yonah).
  • Improved operations with memory and hardware prefetch.
  • L2 Cache is shared by both cores, its size is distributed dynamically depending on the load (we have already seen it in Intel Core Duo).
  • Better power saving technologies.
  • Support for a new set of SIMD instructions, SSE4.

The grapevine provides the following parameters of new processors:

  • 65 nm process technology
  • 1.87-2.93 GHz core
  • 800-1066 MHz FSB (probably 1333 MHz in XE models)
  • 2-4 MB Shared L2 Cache
  • 65-80 Watt TDP

From the same sources not to be revealed here ;), the Core 2 Duo line will be initially represented by the following models:

  • E4xxx series — a single E4200 CPU, 1.6 GHz, 800 MHz FSB, 2 MB Shared L2 Cache.
  • E6300/6400 processors— 1.86/2.13 GHz, 1066 MHz FSB, FSB, 2 MB Shared L2 Cache (note that our engineering sample of the E6400 has a 4MB L2 Cache!)
  • E6600/6700 processors — 2.4/2.66 GHz, 1066 MHz FSB, 4 MB L2 Cache.
  • X6800 processor (eXtreme Edition) — 2.93 GHz, 1066 MHz FSB, 4 MB L2 Cache.

"E" means TDP from 55W to 75W, "X" — above 75W. TDP indexes "T", "L", and "U" are reserved for mobile and Ultra Low Voltage processors of the Core 2 series. We have also heard that the 4xx0 and 6xx0 series will include desktop processors, while the 5xx0 and 7xx0 series — mobile models.

Those microarchitectural details, we could find out with our tests of the engineering sample, can be found in the traditional detailed analysis of the platform in RightMark Memory Analyzer, written by Dmitri Besedin. This article will be published a little later. And the official detailed description of the microarchitecture of the new processor will hardly be available before the official announcement.

Hardware and Software

Testbed configurations

Athlon 64 FX-62
Corsair CM2X1024-6400 (5-5-5-12)
Athlon 64 FX-60
EPoX EP-9NPA3 (BIOS 06.03.30)
Corsair CMX1024-3500LLPRO (2-3-2-6)
Core 2 Duo E6400
Intel DG965SS (eng. sample)
Corsair CM2X1024-6400 (5-5-5-12)
Core 2 Duo E6700
Intel D975XBX (BIOS 1181)
Corsair CM2X1024-6400 (5-5-5-12)
Pentium XE 965
Intel D975XBX (BIOS 1181)
Corsair CM2X1024-6400 (5-5-5-12)
  • Video card — GeForce 7800GTX 256 MB (Gigabyte)
  • Memory — 2 GB (2 modules)
  • HDD: Samsung SP1614C (SATA)
  • Coolers: standard models that come shipped with processors
  • PSU: Thermaltake PurePower 680 APD
Athlon 64 FX-62
Athlon 64 FX-60
Core 2 Duo E6400****
Core 2 Duo E6700
Pentium XE 965
Process Technology
90 nm
90 nm
65 nm
65 nm
65 nm
Core Clock, GHz
Number of Cores
L2 Cache*, KB
FSB clock**, MHz
400 DDR2
200 DDR
266 QP
266 QP
266 QP
Socket AM2
Socket 939
Typical thermal emission***
125 W
110 W
55-75 W
55-75 W
130 W
Virtualization Technology

* — "2x..." means "per each core"
** — in AMD processors it's frequency of the memory controller bus
*** — it's measured differently in Intel and AMD processors, so a direct comparison is not correct
**** — engineering sample, its characteristics may differ from a production-line sample


  1. Windows XP Professional x64 Edition SP1.
  2. 3ds max 7.0
  3. Maya 6.5
  4. Lightwave 8.5 x64 Edition
  5. WinRAR 3.51
  6. 7-Zip 4.32 x64 Edition
  7. LAME 3.98
  8. Monkey Audio 4.01
  9. OGG Encoder 2.8 (Lancer)
  10. Windows Media Encoder 9 x64 Edition
  11. MATLAB 7.1
  12. Pro/ENGINEER Wildfire 2.0
  13. SolidWorks 2005
  14. Microsoft Visual C++ Professional 6.0
  15. CPU RightMark 2005 Lite x64 Edition
  16. F.E.A.R. 1.3
  17. Half-Life 2
  18. Unreal Tournament 2004 build 3339
  19. Quake 4 Point Release 1.1
  20. FineReader Professional 8.0
  21. Adobe Photoshop CS2 (9.0)
  22. Canopus ProCoder 2.01.30
  23. DivX 6.1.1
  24. Windows Media Video 9 VCM
  25. x264 v.438
  26. XviD 1.1.0 Release
  27. Apache 2.0.55 for Windows


  1. NVIDIA ForceWare 81.98
  2. NVIDIA nForce SMBus Driver 4.50
  3. Intel INF Update


Necessary preface to the diagrams

Our test procedure features two peculiarities of data representation: (1) all data types are reduced to one — integer relative score (performance of a given processor relative to Pentium D 805, if its performance is taken for 100 points), and (2) detailed results are published in a table in Microsoft Excel format, while the article contains only summary diagrams for benchmark classes.

3D Modeling and Rendering

Of course, Core 2 Duo E6400 is not as impressive as E6700 — but don't forget that its clock is lower by 25%. The E6700 tears all its opponents to pieces, having outperformed its nearest competitor (AMD Athlon 64 FX-62) by 27% (!). And the FX series from AMD has been traditionally opposed to the XE series from Intel. The only extreme model on Conroe core is not represented here, the E6700 is just a top CPU from a usual desktop series!

CAD (computer-aided design)

On one hand, we can congratulate Intel: its new 2.13 GHz processor outperforms the old top 3.73 GHz model. On the other hand, only Core 2 Duo E6700 can stand up to AMD Athlon 64 FX-60/62. So, CAD/CAE packages are not the most favourite applications of the new core so far. Intel outscores AMD only on a decision. The X6800 will be better, but in this situation AMD can at least hope for catching up with its main competitor, the gap is not too large.


Out of doubt, Intel has made a great progress, compared to NetBurst CPU results. Compared to top Athlon 64 FX processors, the new core also looks good. But AMD can evidently try to wrestle, it has some chance to catch up with Intel (most likely after the upgrade to the 65-nm process technology)...

RightMark Project

The result is not very reassuring, but let's not forget that CPU RightMark is well optimized for all known CPUs. Core 2 Duo does not belong to this group yet, of course.

Processing Bitmap Images (Photos)

Quite a rare case: having demonstrated an excellent result versus the opposing top models, the junior Core 2 Duo... is outperformed by the top Pentium eXtreme Edition based on the NetBurst architecture, everyone already gave up hope in! An excellent reminder to all those people who criticized Pentium 4: yep, this processor is not good for all tasks, but it does not mean that is was bad for all tasks. However, results of the E6700 put everything into place: the Intel platform leads in total score (better by 20% than the top processor from AMD). It's will be much more difficult to close this gap. In order just to catch up with Core 2 Duo E6700, AMD will have to overclock Athlon 64 FX to about 3.4 GHz...

WEB server

That's a great victory, nothing less. The junior Conroe is outperformed by Athlon 64 FX-62 by 5%. But if we take into account that its clock is lower by 31% (!) and have a look at the result of the E6700, it becomes clear that AMD K8 has no chances to catch up with the new processors from Intel in this test, just like in the previous one. Especially as Intel will hardly rest on its oars.

File Packing

That's an utter defeat. When a 2.13 GHz processor outperforms the best competing processor (2.8 GHz) by 7% — that's not a victory on a decision, but a pure knock-out. Judging by what we know about this class of programs and its preferences, the laurel is shared by the Conroe-based processor and Intel chipsets, their memory controllers, to be more exact.

Audio Encoding

Not as peachy as on the previous diagrams. But I repeat that even the E6400 demonstrates a good result for its clock frequency (to say nothing of the E6700, its column is too long to miss :). To all appearances, the situation will be as follows in such cases: top representatives of the Intel Core 2 line will outscore top processors from the main competitor. But AMD will certainly try to close the gap after some time (about six months). In our opinion, the old K8 architecture can still kick, if the gap does not exceed 15% (as in this case).

Video Encoding

And here the AMD position is practically hopeless. Proceeding from the approximate parity between Conroe 2.13 GHz and Athlon 64 FX-62 (2.8 GHz) and assuming that both architectures are perfectly scalable, AMD will have to overclock Athlon 64 FX to about 3.8 GHz in order to catch up with the top Conroe processor (about 2.93 GHz). I don't think it will happen earlier than in a year and a half. By that time Intel will certainly come up with something else.


In fact, you can just reread our comment on the previous diagram...

3D Shooter Games

...And again...

Total score

Efficiency per GHz

This non-standard (for our test procedure) diagram illustrates an evident parameter: efficiency per frequency. These values are just a total score divided by the clock of corresponding processors (in GHz). Here you can see the quintessence of Conroe's triumphal hymn. While the efficiency of Athlon 64 FX is higher by 58% versus Pentium eXtreme Edition 965, Conroe's efficiency is higher by 23% versus Athlon 64 FX! It seemed impossible to create something more efficient than the AMD K8 core, but Intel engineers managed to do it.


On the whole, we can say that the new processors from Intel turned out even more impressive than we expected. Considering that our expectations were quite high. Looking at the results, we don't want to sing the praises, congratulate Intel with the victory, laud the new core, etc. We'd rather look through the diagrams once again to understand what the world giant of CPU building has unleashed. What we'll have to live with :). Conroe and its successors are here for a long time, that's obvious. The efficiency per GHz it demonstrated is not just admirable — there is the reverse of the medal: such impressive results are not obtained easily. So we cannot expect anything cardinally new for at least three or four years. We'll see Conroes with increased clocks and probably with larger caches. There will most certainly appear more cores. But the architecture will hardly change.

What can we say about the architecture looking at the test results? Conroe offers relatively low results in 3D modeling and CAD/CAE packages. Of course, its results are still excellent for its clocks. But they are less impressive than the others. So we partially confirmed the hypothesis that the classical FPU in the new core... no, it's not "bad", but it's less perfect than the other units. CPU RightMark and Adobe Photoshop CS2 also prove that. The manufacturer will probably make up for this problem with higher clocks. Especially as the clock margin is assumably large. The situation in 3D modeling and bitmap graphics can be improved by increasing the number of cores — these algorithms can be easily distributed between multiple cores.

Excellent results are demonstrated by the new core in data archiving, web-server test, OCR, and games. Having analyzed this collection of tests, we can establish a fact that Intel did well for memory and cache operations and well as for "chaotic code" that used to stupefy the long-piped Pentium 4. In fact, the company defeated AMD on its own field with its favourite weapon.

Proceeding from the above-said, I'll risk a global conclusion: from the microarchitectural point of view, the new core will be much simpler for programmers than the previous generation (Pentium 4 / NetBurst). You shouldn't worry much about optimizations (except for distributing computations), you shouldn't keep tabs on critical code fragments for wrong branching predictions or replay threats. Powerful and easy-to-use CPUs, rather unpretentious to code, consuming little power and releasing little heat — that's the ideal offered by Intel and AMD. This unanimity of the two sworn enemies is very important: it means that the general trend of development will remain the same, irregardless of who rules at a given moment. Programs that run well on the new Intel processors will also most likely feel well on AMD platforms, and vice versa. In fact, it really seems the best option from the point of view of a PC (personal computer) equipped with multimedia and other bells and whistles. What concerns various specialized computing farms and intricate software, they can use special hardware.

And of course we should mention the impressive start of the new platform. I cannot recall ever testing a processor of a new architecture, which would categorically cross out all the old ones. Core 2 Duo E6700 is certainly brilliant. As we have already mentioned many times here, Intel can feel unchallenged for at least six months or a year without launching anything new. And if we consider Core 2 Duo X6800... AMD got in a tight. At least in the sector if top desktop solutions. It's high time it should think about a new architecture — Conroe seems too hard for the AMD K8 core, despite our recent optimistic forecasts...

Memory modules for our testbeds are kindly provided by
Russian representatives of Corsair Memory

Stanislav Garmatiuk (nawhi@ixbt.com)
June 15, 2006

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