New Wolfdale Processor Stepping: Core 2 Duo E8600 Review

In 2-3 weeks Intel will start shipping new dual-core processors with new E0 stepping. There will a new CPU among them: the today’s highest frequency model – Core 2 Duo E8600. Our today’s article will talk about this new processor and the features of all upcoming CPUs with the new processor stepping.

by Ilya Gavrichenkov
07/28/2008 | 07:00 AM

What CPUs suit best for contemporary applications – dual- or quad-core ones? It is very hard to answer this question, so no wonder that the adherents of both concepts are constantly engaged into long fierce debates about what’s best. While top quad-core processors work at the same frequencies as the dual-core ones, there are not that many applications out there that could really use their entire potential. On the other hand, dual-core CPUs overclock better, boast more favorable thermal characteristics, and the most important thing – cost considerably less than their quad-core counterparts. That is why many enthusiasts do not hurry to spend their money on Core 2 Quad and Core 2 Extreme processors just yet.


Nevertheless, Intel seems to be working really hard on helping the users with decision making. They try to shift the users’ attention to those models that can offer maximum parallelism. Otherwise how would you explain the fact that they focus more and more on quad-core solutions, pushing dual-core CPUs into the lower-price market segment? For example, since Intel introduced 45nm production process, they haven’t increased the frequencies of their Core 2 Duo processor family even once. As a result, the top quad-core processor models have finally outpaced dual-core processors in terms of clock speeds, which doesn’t seem logical. Here I would also like to add that the new processors with promising Nehalem micro-architecture that are coming out in Q4 2008 should start conquering the market in the quad-core segment first. Thanks to simultaneous multithreading technology (SMT) these processors will be able to process up to 8 threads at the same time. Dual-core CPUs on new micro-architecture should appear in the market more than 6 months later. So those of you who don’t feel like paying extra money for additional cores will have to stay with Core 2 Duo solutions for another considerable while.

Of course, we can’ disregard the fact that Intel’s dual-core processor family is being changed dramatically, especially its lower-end models. Namely, new Wolfdale models with slashed characteristics – E7000 and E5000 – already appeared or will appear there in the nearest future. However, this evolution is meaningful only for users looking for inexpensive computers. It doesn’t take into account the interests of those who shop in $200-$300 price range. But even Intel cannot ignore for a long time this pretty large group of users who need high-frequency dual-core mainstream processors. That is why very soon the company is going to expand their Wolfdale processor family by adding one more high-speed 45nm CPU to the top of the lineup. It will work at 3.33GHz frequency. So our today’s article is going to talk about this new processor – Intel Core 2 Duo E8600.

I have to say that Core 2 Duo E8600 is also extremely interesting because it will be the first processor with E0 stepping. After that the new processor stepping will get into other 45nm Wolfdale processors, too. As a rule, the new cores bring new hopes for even better overclocking potential that is why we all look forward to the test results for the new Core 2 Duo E8600. So, let’s finish our introduction right there and move on to the actual CPU and benchmarks that we all have been looking forward to.

Closer Look at Core 2 Duo E8600

In terms of formal specifications, the new Core 2 Duo E8600 didn’t go too far away from its predecessor. Compared with the Core 2 Duo E8500 that has been the top dual-core Intel processor in the lineup until recently, the clock frequency of the new CPU got only 166MHz higher. Other parameters, such as system bus frequency and L2 cache size remained the same. As for the higher core frequency, they managed to increase it simply by raising the default multiplier to 10x.

The screenshot from the diagnostic utility refreshes our memory with the pretty familiar Wolfdale processor specifications. The Core 2 Duo E8600 bus frequency equals to 1333MHz traditional for the E8000 family, and the L2 cache is 6MB big. There are no surprises in the electrical and thermal parameters, too: the TDP of the new processor is set at a typical value for dual-core CPUs - 65W.

The distinguishing feature of the new Core 2 Duo E8600 is its processor stepping. It changed from C0 to E0, which suggests that the new CPU may boast some new features and functionality. We have every right for these expectations, and Intel describes the innovations introduced in the new E0 processor stepping as follows:

Besides the evident changes in SSpec and CPUID, they also claim that new processors use Halide free packaging and feature innovations reducing system power consumption during low activity. They support PSI signal that the CPU sends out in Deeper Sleep mode. This way the mainboard will be able to lower the power losses in the processor voltage regulator circuitry in idle mode. For example, some advanced mainboards supporting PSI will be able to switch the processor voltage regulator into single-phase mode in this case. For almost the same reason they are going to introduce ACNT2 support – a new software mechanism for determining the processor’s energy status.

New processor stepping will also bring in the long-awaited support modification for the PECI interface that provides access to DTS – digital thermal sensors built into the processor core. I dare hope that these modifications will help free new Wolfdale processor from the widely-spread problem with locked sensor readings.

Here I would like to add that dual-core processors with E0 stepping support new XSAVE and XRSTOR instructions intended to save and restore parameters of the FPU/SSE unit. These new instructions should be primarily beneficial to developers of virtual machine monitor software.

Of course, the exterior looks of the new processors reflects the internal differences of the new E0 stepping. Although the difference is truly minor, you can easily notice it: the components on the bottom of the CPU have been slightly rearranged:

Left - Core 2 Duo E8600 (E0 stepping), 
right – Core 2 Duo E8500 (C0 stepping)

Testbed and Methods

For our processor tests we are going to use a platform built on ASUS P5Q Pro mainboard based on Intel P45 Express chipset. This mainboard demonstrated almost impeccable stability, performance and overclockability, unlike ASUS P5Q3 Deluxe, that we have just finished testing (both review will be posted on our web-site shortly).

The complete configurations of our today’s testbed looked as follows:

ASUS P5Q Pro was tested with the latest available BIOS version 1004. All tests were performed in Windows Vista Ultimate x86 operating system.


We didn’t want to keep you waiting for the most interesting part of our test session, so we decided to check out the new processor’s overclocking potential first. Since Core 2 Duo E8600 with new E0 stepping is Intel’s fastest dual-core processor, it can be easily overclocked by raising the bus frequency thanks to a high 10x default frequency multiplier. However, our tests showed that our processor sample had no FSB Wall until 570MHz FSB, so you shouldn’t expect any problems when overclocking the new processor stepping using lower frequency multipliers.

During our overclocking experiments we decided to find the maximum frequency for our Core 2 Duo E8600 processor when working at its default Vcore of 1.2V.

It turned out that the new CPU has a pretty impressive frequency reserve. Up to 3.9GHz our processor remained absolutely stable. It means that there must be primarily marketing rather than technological reasons for Intel to set 3.33GHz as the default frequency for their new processor. This way Intel will be able to release even faster dual-core CPUs. However, we can hardly expect Intel to speed up its dual-core family any more considering that they focus mainly on quad-core CPUs at this time and besides, there is no competition on AMD’s part. According to Intel’s current plans, Core 2 Duo E8600 will remain the top model in the family for the rest of its life.

Our second experiment was performed with the CPU Vcore increased to 1.4V. FSB Termination and CPU PLL voltages remained at their default values.

Just like with the previous processor stepping C0, Core 2 Duo E8600 proved very responsive to voltage increase. With its Vcore at 1.4V we managed to hit 4.45GHz clock speed.

Increasing Vcore to 1.5V provided even higher results.

At this voltage setting our CPU worked stably at 4.57GHz frequency. It passed a one-hour OCCT stability test as well as Prime95 in Small FFTs mode. During this stress-testing maximum processor temperature didn’t exceed 80ºC according to the readings from built-in thermal diodes.

The frequencies we managed to achieve during our Core 2 Duo E8600 overclocking experiments indicated clearly that the new E0 processor stepping also features higher frequency potential. The Wolfdale processors with previous C0 stepping overclocked in exact same conditions to about 4.4GHz. The new CPU, the first processor on E0 stepping that we have tested so far, managed to hit more than 150MHz higher frequency.

It is very pleasing to know that Core 2 Duo E8600 will be not the only CPU on E0 processor stepping in the market. Very soon Intel will start shipping the already existing Core 2 Duo E8500 and E8400 processors with the new E0 stepping. We can certainly expect these new processors to be able to reach much higher frequencies during overclocking than they used to before.

Temperatures and Power Consumption

Now that we have checked out the overclocking potential of the new Wolfdale CPU on E0 processor stepping, it will be extremely interesting to see how its thermal and electrical characteristics have changed compared with the predecessors. To answer this question we compared the power consumption of systems (without the monitor) built around Core 2 Duo E8500 with C0 processor stepping and Core 2 Duo E8600 with E0 processor stepping.

We measured the system power consumption in three states. Besides our standard measurements at CPU’s default speeds in idle mode and with maximum CPU utilization created by Prime95, we added one more test. It was performed with 100% CPU utilization when both processors were overclocked to 4275MHz frequency obtained as 9.5 x 450MHz FSB. To ensure that the testing conditions are absolutely identical we set the Vcore for both processors at 1.4V. We activated Enhanced Intel SpeedStep and Enhanced C1E Halt State power-saving technologies during these tests.


Core 2 Duo E8500

Core 2 Duo E8600


152 W

151 W

100% Load

194 W

194 W

100% Load, Overclocked

240 W

231 W

As you can see from the obtained results, the new E0 processor stepping can also boast lower power consumption. Core 2 Duo E8600 under workload consumes the same amount of power as Core 2 Duo E8500 with 166MHz lower frequency. The results for overclocked processors show the advantage of the Core 2 Duo E8600 newcomer very clearly: the system with new E0 processor stepping consumes 9W less power than the one with its counterpart with the same Vcore and frequency settings. This is more than convincing.

During our tests we noticed that the thermal sensors of the CPU with new E0 stepping act differently. In idle mode and under maximum workload Core 2 Duo E8600 temperatures were very different from what our test Core 2 Duo E8500 with C0 stepping would demonstrate in the same conditions: they were higher. To illustrate our words here are the temperature diagrams according to the built-in thermal sensors from the first core. The results were obtained during a 15-minute run of the OCCT stability test for both processors overclocked to 4275MHz.

Click to enlarge

Click to enlarge

As you can see, overclocked Core 2 Duo E8600 reports higher temperatures in idle mode and under workload. However, it evidently contradicts the lower power consumption of the new CPU. Therefore, there could be only one conclusion: the diagnostic utilities algorithms need to be adapted for the new implementation of the PECI protocol mentioned among the features of the new E0 stepping.

It could be the fact that digital thermal sensors in the processor cores do not report absolute temperatures, but the difference between the current and maximum safe processor temperature – Tjmax. This Tjmax parameter is not documented anywhere for desktop Core 2 processors, but the utility developers assume it equals 105ºC, judging by the same parameter of the mobile processors. However, looks like new Wolfdale processors with E0 stepping have a different Tjmax value, so the utilities end up reporting higher readings. It is important to keep in mind this peculiarity of the new CPUs.


In our performance tests the new top dual-core CPU, Core 2 Duo E8600, will be competing against its predecessor, Core 2 Duo E8500, and against quad-core Intel processors in the same price range. These are the youngest Penryn models: Core 2 Quad Q9300 and Q9450, and a long-lasting Core 2 Quad Q6600 from the Kentsfield family manufactured with 65nm process.

The base specifications of all our today’s testing participants are summed up in the table below:

General Performance

SYSmark 2007 is an integral test measuring the systems performance when working on typical tasks in widely-spread applications. That is why these results can serve as a description of processors general performance. From this prospective, Core 2 Duo E8600 turned out only a little faster than its predecessor, Core 2 Duo E8500. It is 7% ahead. However, we didn’t expect anything else here, because these two processors only differ by their clock speed.

3D Games

Gaming performance is an important parameter for computer enthusiasts. It is the reason why dual-core processors are still very popular: many gaming titles cannot yet use all the advantages of quad-core processors. Higher operational frequencies of the new E8600 help Core 2 Duo secure its positions in contemporary games.

At the same time, new games optimized for multi-core CPUs should be arriving shortly. The first one like that is Unreal Tournament 3. Here the new dual-core processor with 3.33GHz frequency catches up only with the previous generation quad-core CPU with 2.4GHz clock speed. However, it is a unique situation, so we can’t claim with all certainly yet that Core 2 Quad would be a better choice for games like that than Core 2 Duo.

Video Encoding

Applications optimization for multi-threaded environments matters more and more for video encoding, just like for many other applications. Therefore, Core 2 Duo E8600 will hardly be a good choice here. Especially, if you look at the results obtained with x264 codec that becomes more and more popular.

Other Applications: Rendering, Image Processing, Archiving

As we can see the results of the top dual-core and youngest quad-core processors in our performance test session suggest no definite conclusions about the best processor choice. The recommendations can be absolutely different for each specific case depending on the type of tasks set for the given system. Therefore, the choice of Core 2 Duo E8600 over Core 2 Quad processors should be made in each given situation individually. You can clearly see it not only from the last three, but also from all the other previous diagrams.


Summing up everything we have talked about today, we would like to give up the traditional set phrases about Intel’s success in increasing their dual-core processors performance. It is true, but we believe it is not the most important thing here. Yes, Core 2 Duo E8600 works at 3.33GHz - 166MHz higher clock frequency than that of Core 2 Duo E8500, and it is the highest frequency in the entire Core 2 family. However, it is not the most interesting thing about it. It is much more important that together with the launch of the new processor Intel will introduce into mass market new E0 Wolfdale stepping.

This processor stepping boasts a lot of serious improvements: it supports new power-saving technologies, offers more adequate and stable thermal sensors, overclocks better and is more economical. All these innovations are significant enough for us to strongly advise that you always pay special attention to the processor stepping of the 45nm CPUs you buy to make sure that you only get the latest E0 stepping. Especially, since not only Core 2 Duo E8600, but also other Wolfdale processors with lower frequencies and prices will soon switch to new cores.

In conclusion I would like to add that Core 2 Duo E8600 and other processors with new E0 stepping should appear in the market fairly soon. According to our sources, they will start selling in second half of August, 2008.