Previously we have carried out similar tests using the GeForce GTX 280 and the dual-GPU Radeon HD 4870 X2 graphics card. The Crossfire enabled Radeon HD 4870 X2 results were particularly interesting as they seemed to give the quad-core processors more of an edge over the dual-core parts. Furthermore, the older AMD Athlon64 X2 processors really showed their age when paired with this extreme graphics card.

However a little over a year has passed since that article and many new processors have been released. Although in this first installment we are only covering the Core i7 processor series, next week we will be adding the AMD Phenom II X4 processors, and hope to continue to test more processor series over the coming weeks.

Many of the games that we have selected for this article were picked at random, as we hope to receive a range of interesting results. In the end Batman Arkham Asylum, Wolfenstein, Left 4 Dead 2, Call of Duty: Modern Warfare 2, Company of Heroes Opposing Fronts, Crysis Warhead, Far Cry 2, BattleForge and Tom Clancy's H.A.W.X have been selected.

Please note that although the Core i7 processors only come at clock speeds between 2667 – 3333MHz, we will be testing them at 11 different frequencies ranging from 2000 – 4000MHz. This will give us a bigger picture of how these processors scale when paired with the Radeon HD 5970. Some of the Core i7 results will amaze you, as they did us, while others were as expected.

Interestingly Batman Arkham Asylum only saw a 12% performance decrease when dropping the Core i7 clock frequency from 4.0GHz to just 2.0GHz, which is surprising. That said, this was a 21fps reduction in performance, not that it would be noticed with average frame rates well over 100fps. From 3.6GHz to 2.4GHz we did see just a 4% drop in performance, as just 7fps separated these two configurations.

Although the Radeon HD 5970 was found to be considerably faster than any other graphics cards we have tested in Wolfenstein when we reviewed it last week, it is still the primary bottleneck in this game, at least when paired with a Core i7 processor. For example, we only saw a 3% performance decrease when going from 4.0GHz to just 2.0GHz, which worked out to be a 3fps drop!

The Left 4 Dead 2 results are very similar to those seen when testing with Batman. There was a 13% reduction in performance when going from 4.0GHz to just 2.0GHz, which was a 21fps drop. The biggest gains were seen at 3.8GHz and 4.0GHz, while the biggest drops were at 2.2GHz and 2.0GHz. From 3.6GHz to 2.4GHz there was only a 4% drop in performance, which equated to just 5fps.

Call of Duty Modern Warfare 2 is the first game where we have seen the point where the Radeon HD 5970 truly maxes out. Once 3.2GHz has been achieved, the average frame rate remained locked at 132fps right up to 4.0GHz. The performance started to drop off at 2.4GHz, which means any Core i7 processor will be able to max out the Radeon HD 5970 in Call of Duty Modern Warfare 2.

The Company of Heroes Opposing Fronts results are very similar to those of Call of Duty Modern Warfare 2. The Radeon HD 5970 maxes out early, reaching 109fps at 3.0GHz, while delivering similar results at 2.8 - 2.6GHz. Again when clocked at 2.4GHz and below, the performance does start to drop off, though of course no Core i7 processors are clocked this low anyway and we have simply included the results for interests sake.

Before we ran a single test with Crysis Warhead we knew that this was going to be a heavily GPU limited game. Again the Core i7 processor tops out at 2.6GHz, though even at just 2.0GHz the results are much the same. Although most of today’s games are heavily GPU limited, we were surprised to find that a Core i7 processor clocked at just 2.0GHz would perform so well with the Radeon HD 5970.

Far Cry 2 is another very demanding game, particularly on the GPU, and therefore we were not surprised to find little difference between the 2.0GHz and 4.0GHz processor configurations. In fact, with just 2fps separating them, there is almost no performance difference at all.

In the past RTS (Real-Time Strategy) games have typically provided us with the greatest performance margins in these CPU scaling articles. However this is certainly not the case with BattleForge. Although the Radeon HD 5970 is considerably faster than any graphics card we have ever tested in this game, we still find the results to be heavily GPU limited, as the 2.0GHz configuration matched the 4.0GHz overclock.

Tom Clancy's H.A.W.X is another game that was severely GPU limited, despite using the Radeon HD 5970, and to be honest this surprised us. This was because the Radeon HD 5970 is again considerably faster than any graphics card we have tested in this game, though despite this a Core i7 processor clocked at 2.0GHz is just as fast as the 4.0GHz configuration.

Then we had Company of Heroes and Call of Duty, which only really saw the performance drop off when clocking the Core i7 processor below 2.6GHz, which is a scenario that we are aware will never happen. As mentioned earlier, please note that we have only down-clocked the Core i7 for interests sake and so that we can compare it at a range of frequencies against lesser processors in the near future as we build on this article.

The only two games that showed consistent performance gains from 2.0GHz to 4.0GHz were Batman Arkham Asylum and Left 4 Dead 2. Both games showed roughly a 13% drop in performance from 4.0GHz to 2.0GHz, which is quite insignificant given the reduction in clock frequency. Furthermore, when looking at the performance difference between the 2.4GHz and 3.6GHz configurations we only saw a 3-4% performance drop.

Clearly those with a Core i7 system have little to worry about when gaming with the mighty Radeon HD 5970, and it appears that overclocking will deliver very little in the way of performance gains. That said, Core i7 overclocking is so easy we see no reason not to overclock anyway.

Next week we will be adding Phenom II X4 results to this article, so stay tuned for that. Not only are we interested in comparing the Phenom II X4 performance to the Core i7 processors when scaling with the Radeon HD 5970, but we are also interested to see if the Phenom II X4 shows a greater difference in performance between the frequencies. Following the Phenom II X4 we will look to compare other processor series, such as the Core 2 Quad and Duo processors.

Reviewed By Steven Walton

Having seen how the Intel Core i7 (LGA1366) processors scale with the Radeon HD 5970 from 2.0GHz through to 4.0GHz, we were keen to see how other processor series would perform. For the most part the Radeon HD 5970 was just as fast when paired with a Core i7 920 processor operating at its default frequency, as it was when the processor was overclocked to 4.0GHz!

Surprisingly, out of the nine games tested, just two showed consistent performance gains from 2.0GHz to 4.0GHz, and they were Batman Arkham Asylum and Left 4 Dead 2. Therefore it would seem that the Core i7 processors were more than powerful enough to push the Radeon HD 5970 at full speed before any overclocking took place.

The AMD Phenom II X4 processors are quite powerful in their own right, though it should be noted that they are considerably cheaper than the Core i7 processors and therefore are not in direct competition. Instead the Phenom II X4 processors are more of a direct threat to the Core i5 series, which we will also be looking at shortly.

Many of the games that we have selected for this article were picked at random, as we hope to receive a range of interesting results. The same games that we used to test the Core i7 series will be used again, which include Batman Arkham Asylum, Wolfenstein, Left 4 Dead 2, Call of Duty: Modern Warfare 2, Company of Heroes Opposing Fronts, Crysis Warhead, Far Cry 2, BattleForge and Tom Clancy's H.A.W.X.

The Phenom II X4 processors show a 15% decrease in performance when dropping the frequency from 4.0GHz to just 2.0GHz, which worked out to be a 24fps drop. Something we found interesting is while the Phenom II X4 at 4.0GHz is 6% slower than the Core i7 at 4.0GHz, it is 10% slower when both are clocked at 2.0GHz. In fact, when the Core i7 is clocked at just 2.0GHz, the Phenom II X4 must be clocked at 2.6GHz to deliver the same performance.

The Wolfenstein results are very similar to those found when testing the Core i7 processors. Although there is virtually no difference between the results recorded by the Core i7 and Phenom II X4 processors, we were surprised to find that at 4.0GHz the Phenom II X4 was a frame faster. Although this is hardly a significant performance difference, we did notice that the Phenom II X4 processors did tend to do slightly better clock for clock in this test.

When testing with Left 4 Dead 2 the Phenom II X4 processors really bottom out at 2.6GHz and below, and we saw the frame rates drop right off at 2.0 – 2.2GHz. Again the Phenom II X4 at 2.6GHz delivered similar performance to the Core i7 at just 2.0GHz. With both processor series maxed out at 4.0GHz, the Core i7 was just 3% faster than the Phenom II X4.

The Call of Duty: Modern Warfare 2 results are very similar to those seen in Left 4 Dead 2, and again the Phenom II X4 processors struggle when clocked at 2.6GHz or below. The performance does pick up greatly at 2.8GHz, and we saw steady improvements all the way to 4.0GHz. Interestingly, when maxed out at 4.0GHz, the Phenom II X4 was faster than the Core i7 by a small margin. However it wasn’t until we hit 3.0GHz that the Phenom II X4 was able to overtake the 2.0GHz Core i7.

The performance trends seen in Company of Heroes Opposing Fronts when using the Phenom II X4 were very similar to that of those seen when testing with the Core i7. Once we reached 2.6GHz the results started to level off, though it wasn’t until 2.8GHz was achieved that the Phenom II X4 overtook the Core i7 at just 2.0GHz. While the Core i7 processors maxed out at 109fps at 3.0GHz, the Phenom II X4 was only ever able to reach 102fps, making it 7% slower.

When testing with Crysis Warhead the Phenom II X4 maxed out at 43fps, matching the Core i7. However while the Phenom II X4 met this limitation at 3.6GHz, the Core i7 was able to do so at just 2.6GHz. Furthermore, while we saw just a 3fps difference between the Core i7 at 2.0GHz and 4.0GHz, things were quite different with the Phenom II X4. Rather, there was an 11fps difference between the Phenom II X4 at 2.0GHz and 4.0GHz, and again the Phenom II X4 did not pick up till the frequency hit 2.6GHz.

The Phenom II X4 scaling results are very interesting. While the Phenom II X4 was stuck at 46fps from 2.0GHz to 2.4GHz, it quickly jumped up to 49fps at 2.6GHz, and maxed out at 52fps at 3.2GHz. This is interesting because the Core i7 maxed out at 49fps at 2.6GHz and stayed there. This meant that the Phenom II X4 was actually 7% faster than the Core i7 in this game.

The Core i7 BattleForge results were very unexciting, with the average frame rate locked at 46fps from 2.0GHz through to 4.0GHz. This is quite impressive, as it means the Core i7 is more than powerful enough even at 2.0GHz. The Phenom II X4 results on the other hand were very different, as we saw a 21% increase in performance from 2.0GHz to 4.0GHz. Interestingly, at 3.2GHz the Phenom II X4 was able to match the Core i7’s performance, while it was a single frame faster at 3.6, 3.8 and 4.0GHz.

When testing with the Core i7 in Tom Clancy's H.A.W.X, we again hit a fps limit right off the bat. At 2.0GHz an average of 83fps was achieved, which was the same average frame rate at 4.0GHz. The Phenom II X4 series managed to beat the Core i7, maxing out at 86fps, while 83fps was reached by 2.6GHz. However at 2.0GHz the average frame rate did dip down to 79fps, which meant that there was an 8% decrease in performance.

In games such as Wolfenstein, Call of Duty: Modern Warfare 2, Tom Clancy’s H.A.W.X, BattleForge and Far Cry 2 the Phenom II X4 processors were actually faster when clocked up near 4GHz! This is quite amazing as out of the 9 games tested, the Phenom II X4 series was faster than the Core i7’s in 5 of them. Although the margins were very limited, the Phenom II X4 was found to be faster, and had it just managed to match the Core i7 series with the Radeon HD 5970, we would have been impressed.

While the Phenom II X4 matched the Core i7 in Crysis Warhead, the only games where it failed was Company of Heroes Opposing Fronts, Left 4 Dead 2 and Batman Arkham Asylum. The Phenom II X4 was noticeably slower in these games, making the Core i7 the better choice here. Still, for the most part we found the Phenom II X4 to be every bit as good as the Core i7 processors when gaming with the new Radeon HD 5970.

Having said that, we recommend that AMD users looking at buying this powerful graphics card make sure that they have a Phenom II X4 processor that is clocked at 3.0GHz or greater. Most Phenom II X4 processors are capable of overclocking to 3.0GHz and beyond, while the more high-end options, such as the Phenom II X4 955 and 965 processors, come clocked at 3.2GHz and 3.4GHz respectively.

While we hardly expect there will be many users trying to pair a $600 US graphics card, such as the Radeon HD 5970, with a budget processor, it is nice to see that the sub-$200 US processors are up to the task. The Intel Core i7 920 proved to be more than powerful enough at $280 US, while the AMD Phenom II X4 955 will work just as well at $165 US, giving users plenty of great options.

Reviewed By Steven Walton