by Ilya Gavrichenkov
02/02/2009 | 11:21 PM
The recent launch of the new quad-core Phenom II X4 processor family created a real commotion not only the among AMD fans but also in the rest of the computer community. Not only AMD fan forums, but also some reputable technical publications sounded extremely excited about the new 45nm processors from Stars (K10) family. They pronounced the arrival of a new milestone product and resumed aggressive competition between AMD and Intel. In the meanwhile, a sensible view of Phenom II X4 features doesn’t really give us a lot of reasons to be that optimistic. Our recent extensive performance tests of these new processors showed that they can only be regarded as an alternative to the cheapest quad-core Intel CPUs and only with a certain proviso. Of course, compared with the old Phenom X4 CPUs, the frequency potential of the new 45nm cores in the new Phenom II X4 helped significantly increase their performance and improve their power consumption and heat dissipation characteristics. However, it was still not enough for AMD Phenom II processors to look as an indisputably better choice against the background of Intel Core 2 Quad. The only thing we can state with certainty is that Phenom II X4 processors are comparable only with quad-core Intel Core 2 Quad from the inexpensive Q8000 series.
Trying to make their new products more attractive, AMD stresses their good overclocking potential. It is true, during our test session we checked out Phenom II X4 940 from the Black Edition series that featured an unlocked clock frequency multiplier. We managed to easily overclock this processor from the nominal 3.0 GHz to 3.8 GHz with air-cooling alone. But unfortunately, even this achievement doesn’t make AMD Phenom II X4 processors more attractive than the competitor’s solutions. For example, after the recent price changes Core 2 Quad Q9400 processor costs almost the same as Phenom II X4 940 and they can overclock to the same 3.8 GHz with air cooling involved. However, they demonstrate higher performance due to “broader” Core micro-architecture that allows processing more instructions per clock.
At the same time, these arguments do not mean that those computer enthusiasts who use overclocking to achieve maximum performance should once and for all forget about AMD CPUs. However, they should be looking not at the top Phenom II X4 940 model, but at the cheaper Phenom II X4 920 CPU. It is priced comparably to Core 2 Quad Q8300, which features lower performance-per-megahertz than Core 2 Quad Q9400 because of smaller cache memory. Moreover, it doesn’t overclock as well as the latter because of the low multiplier. So, if Phenom II X4 920 processors can boast frequency potential not too much lower than that of their superior counterparts, they may have every chance to become the most optimal overclocker solution in their price range.
Our today’s article will discuss this particular matter in detail. We are going to try answering the question if AMD Phenom II X4 920 processor is a smart choice for an overclocker platform. Moreover, we are going to provide some practical recommendations on the best ways of achieving maximum overclocking results with these CPUs that have no unlocked frequency multiplier.
AMD sent us their top model – Phenom II X4 940 Black Edition – for our first article devoted to new Phenom II X4 processor family. This CPU works at 3.0 GHz nominal frequency and features an unlock clock frequency multiplier. The second model is the junior model in the family – Phenom II X4 920. It is designed to work at lower nominal clock speed of 2.8 GHz. As for other characteristics, it is not very much different from the top model, which is actually not surprising at all, as both Phenom II X4 CPUs are based on the same 45nm Deneb core and are designed for Socket AM2+ intrustructure.
Therefore, the formal specifications are quite logical:
AMD Phenom II X4 920
4 x 512 KB
Dual-channel DDR2 SDRAM
Supported memory types
North Bridge frequency
HyperTransport bus frequency
1.8 GHz (HyperTransport 3.0)
45 nm, SOI
Maximum packaging temperature
SIMD instruction support
MMX(+), 3DNow!(+), SSE, SSE2, SSE3, SSE4A
Like Phenom II X4 940, Phenom II X4 920 uses the same frequency for its built-in North Bridge - 1.8 GHz, and supports the same memory types including DDR2-1067 SDRAM. The typical heat dissipation of both these processors is also the same and is set at 125 W. So, Phenom II X4 920 selling for $30 less than its elder brother does in fact yield only in one parameter to the 940 model: it has lower nominal clock frequency.
Besides, AMD didn’t include their Phenom II X4 920 CPU into the Black Edition series. In other words, there is no way to overclock Phenom II X4 by simply raising its multiplier. On the one hand, it is pretty sad news for overclockers. But on the other hand, it doesn’t really eliminate any overclocking prospective, but simply means that Phenom II X4 920 should be overclocked by raising the base clock generator frequency, just like you would do with Intel CPUs.
You may think that overclocking AMD processors by raising their clock generator frequency is well-studied approach that has been in successful use since first 64-bit Athlon 64 CPUs appeared in the market. However, it is not quite the case. The launch of quad-core AMD processors together with the introduction of Stars (K10) microarchitecture changed a lot about the way we overclock. It happened due to the introduction of an L3 cache shared among all cores and the modification of the voltage regulator circuitry. That is why Phenom overclocking procedure has certain peculiarities that need to be taken into account when you overclock Phenom II processors based on new 45nm cores.
In order to correctly understand all peculiarities of an overclocked Socket AM2+ platform functioning, you should keep in mind that these systems use several independent frequencies at the same time:
All these four base frequencies are connected with one another, they are all set by one base clock generator. However, the exact values are determined by the corresponding multipliers. This dependency formally looks as follows:
All four multipliers are completely independent and may be changed in the mainboard BIOS Setup. The only condition that you should keep in mind when changing the frequencies of different components is that the HyperTransport bus frequency is at all times lower than the frequency of the North Bridge integrated into the CPU.
The base clock generator frequency marked as [HT Reference clock] in the formulas is set at 200 MHz by default. [CPU Multiplier] is determined by the nominal frequency of a specific model but can be adjusted on Black Edition CPUs. [HT Multiplier] and [NB Multiplier] are set to 9x or 10x by default, but in reality they can vary within a much broader interval. As for the supported value range for the memory frequency coefficient, ensures CPU compatibility with DDR2-400/533/667/800/1067 SDRAM at nominal base clock generator frequency.
For example, for the Phenom II X4 920 processor discussed today, working with DDR2-1067 SDRAM:
As it follows from everything we have just said above, overclocking of contemporary AMD processors is possible not only by changing their multipliers, but also by increasing the clock generator frequency over 200 MHz. Since the clock generator is located on the mainboard, its frequency can be changed in the mainboard BIOS Setup; it is not detected or blocked even in non-Black Edition CPUs.
However, it is important to understand that by raising the clock generator frequency you will not only push up processor clock speed, but will also force the memory bus and HyperTransport bus frequencies to increase appropriately. It will also affect the operation of the L3 cache. All these factors may in the end restrict overclocking success. However, luckily, you can always use special settings in the mainboard BIOS Setup to eliminate these obstacles by lowering the corresponding coefficients.
Moreover, you can also increase the voltage of the main system components in order to improve their frequency potential during overclocking. Although these measures increase not only the frequency potential but also heat dissipation and power consumption, proper cooling will make them an important part of the successful overclocking procedure. There are three voltages that matter most of all for platforms built around processors on Stars (K10) microarchitecture:
Everything we have just said makes the general rules of Phenom and Phenom II overclocking pretty evident. The most important part of the procedure is increasing the clock generator frequency. The resulting CPU clock speed depends on it linearly via the clock frequency multiplier of the specific CPU model. When you overclock these processors, you should make sure that the frequencies of the integrated North Bridge and HyperTransport bus do not exceed 1.8 – 2.0 GHz, that is why you have to lower the corresponding multipliers as necessary. The same is true for the DDR2 SDRAM frequency multiplier: the actual memory clock speed shouldn’t exceed the physical potential of the memory modules used, which may call for lowering the multiplier determining this frequency setting.
In addition, you may increase the CPU core voltage to improve the overclocking results even more. In this case, however, you should pay special attention to proper heat dissipation and install an efficient cooler.
To find out the overclocking potential of Phenom II X4 920 processor we put together the following test platform:
First of all we checked out how the CPU would overclock without increasing its core voltage over the nominal 1.35 V. It turned out that our sample could overclock to 3.36 GHz by simply increasing its clock generator frequency. Even without any voltage adjustments the system remained stable at up to 240 MHz clock generator frequency setting.
Note that we had to lower the multipliers for the HyperTransport bus and integrated North Bridge frequencies to 8x, so these frequencies stayed at 1920 MHz, which is pretty close to their nominal values. The same way we used 4x multiplier (corresponding to DDR2-800 in nominal mode) for the memory frequency. So, we overclocked our memory to the level of DDR2-960 SDRAM.
However, the results obtained without any voltage increase are only interesting if you are not ready to deal with considerably higher power consumption and heat dissipation during your overclocking experience. We decided not to stop at that point and pushed the CPU core voltage to 1.55 V to hit even greater results.
Increased Vcore provided additional room for further CPU frequency growth, so we could get our processor to run stably at 3.72 GHz. It was obtained by raising the clock generator frequency to 266 MHz.
I have to point out that once we confirmed processor operational stability in this mode by running OCCT 3.0.0.b23 utility for one hour, we decided to overclock the North Bridge built into this CPU, too. When we increased its voltage to 1.4 V, it could work just fine with 8x multiplier, i.e. at 2120 MHz frequency.
So, our Phenom II X4 920 revealed almost the same overclocking potential as the Phenom II X4 940 Black Edition we tested before. Luckily, the locked clock frequency multiplier of the junior model didn’t become a serious problem during our overclocking experiment. We managed to uncover the hidden Phenom II X4 920 potential by raising the clock generator frequency. As a result, we could speed up this processor 33% over the nominal value, which is a very good achievement.
Unfortunately, it is not possible to adequately estimate the thermal mode of a CPU overclocked that far. All diagnostic utilities report evidently lower temperatures of Phenom II X4 cores. Nevertheless, we are going to offer you a chart showing temperatures of one of the processor cores during OCCT 3.0 stability test.
Click to enlarge
According to the results on this diagram, the core temperature under load doesn’t exceed 45-50°C. However, the results obtained in idle mode suggest that we need to add another 5-10°C to these numbers. Until we get some explanation from AMD, we can’t really offer you a more specific picture, unfortunately.
Another peculiarity of Phenom II X4 overclocking is connected with Advanced Clock Calibration (ACC) technology. Some data suggest that it allows reaching higher overclocking results with previous-generation Phenom processors on mainboards featuring ATI SB750 South Bridge. Although it is formally supported by the new Phenom II CPUs, too, we don’t see any improvement with ACC activated anymore. Not only our own tests, but also the comments from AMD engineers confirm this finding. So, when you attempt to overclock the Phenom II processors, you can disable ACC technology in the mainboard BIOS without any hesitation.
In conclusion to our discussion of Phenom II X4 920 CPU overclocking I would like to remind you that there is AMD Overdrive utility that allows overclocking these processors not only through the mainboard BIOS Setup, but also from Windows. AMD was going to prepare a new version of this utility taking into account the peculiarities of the new processors by Phenom II launch. For some reason the new version was never released. Luckily, the previous version 2.15 of AMD Overdrive worked just fine with Phenom II X4 and can be used to change the settings and find the most optimal parameter values.
However, AMD Overdrive 2.15 does in fact have some problems with the new Phenom II CPUs. For example, this utility couldn’t correctly identify processor Vcore and didn’t report the correct core temperatures, just like a bunch of other utilities.
Now that we know how far our Phenom II X4 920 can be overclocked with air-cooling, we decided to check the performance level we could achieve with an overclocked CPU. The main goal was to find out if the new AMD processor could become a better buy for overclockers than quad-core Intel CPUs from the same price range. So, the main action during this test session will be about the side by side comparison of Phenom II X4 920 overclocked to 3.72 GHz against overclocked Core 2 Quad Q8300 and Core 2 Quad Q6600. Intel set the price point for these processors at $183, while Phenom II X4 920 is officially priced at $195. Moreover, we have also included a more expensive Core 2 Quad Q9300 processor. Although it has almost completely disappeared from the official price-list, it is still retailing widely for a somewhat higher price than that of Phenom II X4 920.
As we have already mentioned in our previous reviews, the overclocking potential of junior Intel processors from Q8000 and Q9000 series is determined not by the frequency potential of the semiconductor dies, but by the ability of the chipsets and mainboards to ensure stable operational conditions at high FSB speeds. Therefore, we decided to test our Core 2 Quad processors with a popular ASUS P5Q Pro mainboard. It allows increasing the FSB frequency to 475 MHz for quad-core processors. So, Core 2 Quad Q8300 and Core 2 Quad Q9300 with a 7.5x multiplier were overclocked to 3.56 GHz (7.5 x 475 MHz) in order to be able to compete against Phenom II X4 920. It is the average frequency the owners of these processors can count on.
The previous-generation quad-core Intel Core 2 Quad Q6600 processor is initially designed to work with 266 MHz bus, so its multiplier is higher and equals 9x. So, its overclocking potential was not limited by the mainboard, although high heat dissipation wouldn’t let us push its frequency over 3.6 GHz (9 x 400 MHz).
To get a general idea of overclocked processors’ performance we included a few high-end CPUs in their nominal mode: Core 2 Quad Q9650, Core i7-920 and Core i7-940. You will also see the results demonstrated by Phenom II X4 920, Core 2 Quad Q8300, Core 2 Quad Q9300 and Core 2 Quad Q6600 processors in their nominal mode. They will help us estimate the performance gain from overclocking.
As a result, we put together three different platforms on 7 processors:
1. AMD Socket AM2+ platform:
2. Intel LGA775 platform:
3. Intel LGA1366 platform:
Four processors out of seven were tested not only in their nominal mode but also during overclocking:
The results in the complex SYSmark 2007 test turned out not quite optimistic. Overall, even though Phenom II X4 920 outperforms its direct rivals in nominal mode, overclocking changes this picture. Even Core 2 Quad Q8300 processor overclocked to 3.57 GHz outperforms Phenom II X4 920 working at 3.72 GHz. On the one hand, it once again indicates that Intel processors boast better IPC (instructions per clock), but on the other – shows that Intel CPUs boast higher frequency potential, even though it is not fully revealed. While Phenom II X4 920 overclocked by 33%, Core 2 Quad Q8300 reached 43% higher frequency when it was stopped by the mainboard’s inability to catch up.
However, things are a little different in certain type of applications. For example, overclocked Phenom II X4 920 processor is a little ahead of Core 2 Quad Q8300 in E-Learning scenario working with vector and raster images, PowerPoint presentations, PDF-files and flash-videos. And it almost catches up with the overclocked Core 2 Quad Q9300 in Productivity scenario that works with Microsoft Office suite.
At first glance, the new AMD solution seems to be winning in 3D games. Phenom II X4 920 working at 3.72 GHz outperforms its major Core 2 Quad Q8300 competitor in every single test we used. However, it most likely happens due to seriously cut-down cache-memory of the Intel CPU. That is why when we compare the performance of our Phenom II X4 920 against that of an overclocked Core 2 Quad Q6600, the outcome is no longer in AMD’s favor: even though Q6600 processor belongs to the previous generation, it features an 8MB L2 cache.
Overall, we are not really talking about any serious performance differences. Overclocked Phenom II X4 looks quite well and demonstrates very good performance. Nevertheless, I have to say that overclocking a $200 quad-core processor will not provide the users with the same performance that they could get from higher-end more expensive CPUs, even working at their nominal speeds.
Video encoding is the best application for the new AMD processors. Phenom II X4 920 outperforms its rivals in nominal mode as well as during overclocking. By the way, at 3.72 GHz it also outperforms Core 2 Quad Q6600. However, it is still very far behind the impressive results demonstrated by Core i7 CPUs. No wonder, since SMT technology implemented in the latest Intel solutions matters here a lot.
It is pretty hard to put together a single verdict at this type of workload. As you can clearly see from the diagrams, everything depends on the rendering application. Nevertheless, we can’t help stressing the impressive results of Core i7 CPUs: they are evidently the best choice in easily paralleled computational tasks. No doubt about that.
Fritz and Folding@Home are another two examples where “pure” computations power of the CPU is important. So processors with higher IPC win in these tests, and Phenom II X4 920 is evidently not one of them. Overclocking Phenom II X4 920 doesn’t help here either. The only consolation is outperforming a much more expensive Core 2 Quad Q9650.
The situation in Photoshop is also not the best for Phenom II X4 920. With or without overclocking, it yields to its main rival – Core 2 Quad Q8300.
However, the results of the WinRAR test will be a real pleaser for AMD fans. The new AMD CPU as always scores very high in this application.
Our Phenom II X4 920 performance tests showed that it may be a very good choice for an overclocker platform. But before we draw any final conclusions, let’s see if it turns out as power-efficient as Intel CPUs. So, we measured the power consumption of a system (without the monitor) built around AMD Phenom II X4 920 in its nominal mode and during overclocking and compared these results against similar platforms built with Intel CPUs from the same price range, namely, Core 2 Quad Q8300, Core 2 Quad Q9300 and Core 2 Quad Q6600.
During this test session we loaded the CPUs using Prime95 utility. Besides, we activated all power-saving technologies, such as C1E, Cool’n’Quiet and Enhanced Intel SpeedStep, to make sure that the power readings in idle mode were correct. It is important to remember that Enhanced Intel SpeedStep is implemented in such a way that during overclocking it doesn’t change the processor core voltage, but still lowers their frequency under low workload. AMD Cool’n’Quiet technology, however, is fully operational even in an overclocked system.
Phenom II X4 920
Core 2 Quad Q6600
Core 2 Quad Q8300
Core 2 Quad Q9300
Phenom II X4 920 @ 3.72GHz
Core 2 Quad Q6600 @ 3.6GHz
Core 2 Quad Q8300 @ 3.56GHz
Core 2 Quad Q9300 @ 3.56GHz
Unfortunately, new AMD processors still lose to alternatives from Intel even though they are now manufactured with more advanced 45nm process. Even in nominal mode a system on Phenom II X4 920 processor consumes 20-30 W more than similarly performing platforms on Intel CPUs. In fact, power-efficiency of the new Phenom II X4 processors improved only compared to the previous-generation quad-core Intel processors manufactured with 65nm process that are still widely available in retail.
During overclocking, the situation is not any better for AMD offering. Although Phenom II X4 920 boasts fully operational Cool’n’Quiet technology in overclocked mode, even in idle mode the system built on it consumes more power than Core 2 Quad Q8300 and Q9300 based platforms. When the CPU utilization hits 100%, the power consumption difference turns more than serious and reaches 70-80 W. Moreover, power consumption of an overclocked Phenom II X4 920 based system is almost the same as that of Core 2 Quad Q6600 (3.6 GHz) based system.
However, there is a very logical explanation why the new AMD CPU didn’t impress us with its power consumption readings during overclocking. Even though Phenom II X4 processors use 45nm cores, they require much higher Vcore than Intel processors.
Phenom II X4 processors didn’t bring the desktop performance to any revolutionary heights. Unfortunately, even new manufacturing process doesn’t let AMD design CPUs that could successfully compete against Intel solutions in all price segments. And although the clock frequencies of the new AMD processors increased significantly, their performance turned out limited by the Stars (K10) microarchitecture potential, because it boasts lower IPC than the current Intel microarchitecture. Phenom II X4 920 we have just discussed is a great illustration to everything we have just said. At its nominal 2.8 GHz it can only compete against Core 2 Quad running at 2.4 – 2.5 GHz frequencies. Only smart pricing strategy helps AMD here: they positioned Phenom II X4 920 in such a way that it turns out a little better than the identically priced Core 2 Quad models.
However, overclockers have their own perception of the situation. They are primarily interested in the processor’s ability to work in modes other than nominal. And here the new Phenom II X4 appeared much more attractive than their predecessors. We could easily overclock our Phenom II X4 920 processor by 33% clock frequency without any sophisticated cooling involved. At this frequency our CPU was on average faster than an overclocked Core 2 Quad Q8300. This result certainly makes quad-core Phenom II X4 920 a good overclocking choice in the sub-$200 price range.
However, you shouldn’t overestimate the overclocking potential of Phenom II X4 920 processor, because Core 2 Quad Q8300 is far not the strongest competitor in the Intel camp. For instance, the similarly priced Core 2 Quad Q6600 can hit much higher frequencies than Core 2 Quad Q8300, even though it belongs to the previous generation. So this processor can be on average faster than Phenom II X4 920 working at a higher frequency, too.
Another weakness of the new Phenom II X4 920 processor, which stands out more during overclocking especially, is high power consumption. According to our tests, at 3.72 GHz it falls far behind more power-efficient Intel processors from Q8000 and Q9000 series. In fact, it almost catches up with Core 2 Quad Q6600 here.
Nevertheless, we are extremely pleased with the results demonstrated by Phenom II X4 920. Although it didn’t outperform the similarly priced Core 2 Quad dramatically, we can’t say that it yields a lot to its rival, either. And it means that AMD has every chance to become quite popular among overclocking fans due to their new 45nm processors.