AMD has had mastery of the budget end of the processor market for some time now for reasons including price/performance, low motherboard prices and platform longevity (they don’t change sockets at the drop of a hat). Our aim today is not just to look at the performance of an AMD Athlon II X4 630 and its architectural efficiency against a similarly clocked Intel processor but also (and more importantly) to run tests to predict the performance of forthcoming processor ranges such as the “Bulldozer”. We will do this by running tests with 1, 2, 3 and all 4 cores enabled which will give us accurate results for a dual-core X2 processor and use extrapolation to approximate the performance of a 6-core X6 “Bulldozer” processor.

By spending a long time duplicating our tests four times we are able to see how various applications perform with differing numbers of cores allowing us to establish the multi-core efficiency of games such as Far Cry 2 and benchmarking tools like 3D Mark Vantage. The testing is by no means comprehensive and if we had 2-3 weeks to spare we could have tested every recent game and application for completeness so our apologies in advance if your favourite application is not included in our representative sampling.

Of more universal interest is comparing the efficiencies of the latest Intel and AMD architecture to compare current and future efficiencies and predict how future trends and architectures (such as the reduction of floating point capability in AMDs new “Bulldozer” architecture and moves toward CPU/GPU convergence) will affect performance.

Processor Architecture

First, a recap of the X4 Phenom 2 architecture and layout:

As with other Athlon II processors there is no L3 cache (the above diagram is for the Barcelona die). Our estimate is that there will be roughly a 10% performance penalty for this. AMD no doubt consider the reduction in selling price to be more than sufficient to offset this.

The CPU

On the left is the Intel Core i7-870 and on the right is an AMD Athlon II X4 630 of a similar speed. The 45nm Nehalem core is smaller than its AMD counterparts or perhaps the AMD heat spreader is just larger on purpose. Lynnfield is slightly larger than it older Bloomfield predecessor due to the inclusion of an onboard PCIe controller.

One of the features of the socket 1156 (and socket 1366) design is that the pins are on the motherboard socket and not the processor shell. This has the benefit of not risking bent/broken pins during transportation and handling (we testers at The Hardware Review are known for being somewhat ham-fisted with large fingers but have never had any problems handling CPUs over the last 20 years). The drawback of Intel’s design is that extra pressure is placed on motherboard manufacturing – an area where components are usually selected for their low cost. A recent example is the spate of damaged FoxConn sockets due to poor contact with the CPU. It is difficult for motherboard manufacturers to adhere to Intel’s high standards of quality control when they source components from many suppliers. The FoxConn problem has been resolved and all socket 1156 boards using FoxConn sockets now on the market should be using the revised socket (the version number is listed on the back of the PCB so there is no way to know for sure before purchase so it may be worth contacting the manufacturer to allay fears if necessary. The AMD CPU pins are stronger and sturdier and the platform suffers from non of the problems of the Intel processor motherboards.

The Problem with Multi-Tasking

Since this review is primarily about multi-core efficiency it worth explaining the inherent problems with multi-tasking. This may surprise some readers as we already have supercomputers made up of thousands of Intel or AMD processors and if they did not scale well then research institutions would not buy them to predict climate change, where minerals are buried and so on. The reason they work so well is that it is easy to split millions of operations among thousands of cores. Splitting one thread across multiple cores is actually quite difficult.

The problem involves concurrency, monitors and semaphores and is too involved to go into here although interested readers are encouraged to read the Wikipedia article on “Dining Philosophers” which explains the whole problem in easy to visualize terms. It can be found here.

Until Quantum Computing is viable we will have to rely on programmers making allowances for multiple cores and programming accordingly. Some games and applications are already optimized to a limited degree for multiple cores and theoretically every application will get a boost with a second core, even if just by offloading the usual Windows background processes to the other unused core.

It has been clear for some years that frequencies cannot continue to increase due to manufacturing limits and have remained roughly constant around the 3GHz mark for about 6 years. Instead it seems that the future gains will be attained by increasing the number of cores in a CPU, whether physical or also virtual (as with HyperThreading). Our test will aim to show which architectures are most suited to getting the best out of extra cores, where the bottlenecks are and, hopefully, give an indication of how the architecture will scale in the future as number of cores increase.

Test Results

The results show fairly linear scaling as we go up in cores. It should be noted that synthetic tests such as SiSoft Sandra will scale quite well and are mainly useful as an indication of bottlenecks and to see what programmers can achieve if they overcome the hurdles they face.

The processor multimedia results also scale well although real-life differences will not be as pronounced as this chart indicates.

Interestingly, the memory bandwidth results show that a single core cannot make full use of available capacity and is particularly the case for the AMD Athlon II architecture. Dual core or higher is required to overcome this limitation.

Despite this test favouring processors with HyperThreading (i.e. Intel ones) there is a huge difference in performance between the two architectures. While two cores are fine for the Intel Core i7-870 here, the AMD Athlon II X4 630 needs at least 3 to put in a reasonable showing. Since graphics performance is similar (same GPU after all) the limitations lie with the processor. This bodes well for the forthcoming Clarkdale dual-core processor but it will be necessary to see this repeated in real-world benchmarks to draw any firm conclusions. The AMD Athlon II X4 630 performance scales better though, so when using all 4 cores there is not a huge difference between the Athlon II X4 630 and the Intel Core i7-870 despite the latter being 3 times as expensive.

Far Cry 2 has a very useful built-in benchmarking tool with many configurable parameters.

First thing to note is that this game is playable with 8x AA on any number of cores (fortunately a single-core Athlon II does not exist). We will test at varying resolutions later on.

HAWX is a bit of a strange game but provides a consistent benchmarking function. At 1280×1024 with 8x AA on the highest settings we can see that a 2-core Intel i7-870 outperforms an Athlon II X4 630 with all 4 cores at maximum. There does however appear to be a bottleneck that could be resolved with more efficient programming.

Two things are noteworthy. There is a bottleneck on the i7-870 performance but its high enough to not be an issue. More importantly it takes the Athlon II X4 630 at least 3 cores to match the performance of a single i7-870 core but with all 4 cores active can match the best the i7-870 has to offer.

Now we have compared differing numbers of cores, it’s worth showing the performance of the above games with all 4 cores active but at differing resolutions to show the maximum performance that can be expected.

Suddenly, things are not so bad and both processors can run at good speeds at all resolutions. If we had not tested with different numbers of cores we would not be able to tell from the above results that a 2-core Lynnfield runs this game just as well as a 4-core one and that the AMD processor needs at least 3 cores to keep up.

Performance is virtually identical across differing resolutions hiding the issue with a single AMD core. This is a game that will not tax even basic systems.

Here the AMD Athlon II X4 630 outperforms the Intel i7-870 slightly at higher resolutions but hides the previous results showing poor performance with 1 and 2 cores.

Conclusion

We’ve done something not seen in other reviews and looked at the multi-core efficiency of the latest architectures from Intel and AMD (these architectures will change next year and will need re-appraisal) and looked beyond the simple results of just running benchmarks at default (and sometimes overclocked) speeds.

By using the motherboard BIOS to selectively disable cores we can look at the per-core performance which gives us a much greater insight into the architecture’s potential than just interpreting the results from the more traditional benchmarks.

It’s clear that in many cases AMD really need a 3-core processor to get reasonable performance. Of course Intel and AMD are aware of this which is why AMD released their X3 range and why Intel is about to launch its i3 (X2) range.

Comparing the X4 630 with a high end Lynnfield processor costing 3 times as much seems completely unfair but the AMD processor held its own very well. We have criticised the performance of one and two cores but the processor comes with 4 cores and it performs admirably with all 4 cores active. Even more promising is the scaling of cores that is not matched by the Intel Lynnfield architecture and bodes extremely well for the forthcoming “Bulldozer” range.

Another reason we would recommend the X4 630 over an X3 processor despite our observations, is that having spoken to some developers, future games are being designed to stress all 4 (or more) cores. Then there are the applications that will always max out multi-core processors such as video editing, media encoding and other specialist segments that will always benefit from greater parallelism and those users may be drawn to high end 4 core systems (like Intel’s socket 1366). But increasingly, especially given the high price of putting together a socket 1366 system, an AMD X4 system will do fine for home users editing DVDs or HD Video of birthdays etc. and will be a fraction of the price.

When we look at all factors, we can see that the price/performance of the AMD Athlon II X4 630 is unmatched and there is really no reason to not pay an extra $10 to get a X4 instead of a X3 processor, in even a budget system. Platform longevity is ensured as a “Bulldozer” processor can be dropped into the system as an upgrade at a later date whereas the more expensive i7-870 cannot be upgraded to 6-core “Gulftown” processors as they are only supported on socket 1366.

AMD maintain their hold at the value end of the market. With the AMD “Bulldozer” being expected soon it will be interesting to see how things develop over the next few months.

Amar is the founder and Editor of The Hardware Review (http://www.hardwarereview.net).