Building a more balanced rig
As soon as you set out on this sort of endeavour, you know there will be compromises. For instance, slipping AMD's kit into three neat little categories - bargain basement, mid-range and high-end - helps to quantify the argument. But it's also very restrictive.
That's especially true when it comes to maximising your budget for gaming performance. The total price gap between our bargain basement solution and the mid-range option, for example, is around £120. That's spread across CPU, GPU and motherboard.
But what if you stayed the course with the AMD FX 4170 processor and Gigabyte 970 mobo and dropped in a Radeon HD 7950? Could AMD's entry-level FX chip cope? Would it be graphics overkill?
The same applies for the step from mid-range to high-end. The delta's even bigger there, clocking up to £160 for graphics, processor and motherboard. It's certainly tempting to slap that all into graphics. But again, is the lower specified processor and motherboard up to the task? Let's find out.
In the interests of maintaining a little suspense, let's kick off with the midrange option. To recap, the default setup here is: AMD FX 6200, a six-core effort with 3.8GHz/4.1GHz Turbo clocks, and MSI's 990XA-GD55 motherboard. The natural partner in terms of graphics feels like a Radeon HD 7800 board of some flavour and it was the 7870 GHz Edition we went for.
But what happens when you sling in some 7900 Series silicon in the shape of a Radeon HD 7950? The answer is that it depends on the game in question. But get this: the worst-case scenario is that you get games performance at least as good as the full-on high-end platform complete with 990FX motherboard and eight-core FX 8120 processor.
In Metro 2033, the most demanding of our gaming quartet and, therefore, the title that provides the most critical baseline, the mid-range mashup delivers identical results across the board to the pure high-end solution. There's not a lot in it in Max Payne 3, either.
Most likely, that's because these are games predominantly limited by GPU performance. Elsewhere, the CPU comes into the equation and that's when the combo of mid-range CPU and high-end graphics is actually more effective. DiRT Showdown with anti-aliasing and global illumination disabled is probably the best example here. The full high-end rig scores 61 frames per second versus 67 for our mid-range mashup.
Counter intuitive? It would be if games were like video encoding and scaled neatly across as many cores as you throw at 'em. But they're not, so the explanation very likely centres on the 6200's significantly higher clocks. It's true that they're very close in terms of maximum Turbo speed. But that only happens with a single core under load. While most games won't generate infinite CPU-intensive threads, most are capable of at least a few.
That's the worst possible scenario for the eight-core FX 8120 - enough threads to prevent full-speed turbo but not enough to capitalise fully on its extra cores.
With that in mind, the prospect of a low-end CPU and high-end graphics doesn't seem so crazy after all. Remember, the FX 4170 has the quickest clocks here, buzzing along at 4.2GHz even with all four cores loaded. Could the cheapest CPU actually be the best?
In a word, no. When it's the graphics card throttling performance, for instance Metro 2033, the 4170 does just fine. But in less demanding games, a gap does emerge. It's not necessarily a crippling, deal-breaking delta in performance. But if our benchmarks are anything to go by, you'll be limited to around 45 frames per second in most games. That's tolerable today, but you've absolutely no margin left for the ever more CPU-intensive titles that will inevitably appear in future.
But the killer blow for the 4170 involves pricing. It's simply not available at a big enough discount. You'd be insane not to go for the six-core 6200 for the extra tenner. The choice between the 6200 and the full-on eight-core 8120 is more nuanced.
Again, the price gap is modest, with £20 between them. We'd be tempted to go with the 8120 and crank up the clocks a little. But the argument is finely balanced.
At this stage, we're getting awfully close to an overall conclusion. But there's still one question we haven't directly addressed. Is there anything to AMD's claim that there's a direct, tangible benefit to a pure, end-to-end AMD setup?
It's difficult to get a completely definitive answer here. But we've mixed and mashed with a view to flushing out as many facts as possible. Along with the three AMD platforms, the two mashups we've already discussed above and the reference Intel-plus-Nvidia shebang, we added a few more combos to the mix.
We've got the Intel Core i5-3570K running with an HD 7870, the AMD FX 6200 with AMD GeForce GTX 660 Ti and the FX 4170 with a GTX 460. And the results? In truth, they're inconclusive.
The most direct comparison is the Core i5 and the FX 6200, both running Radeon HD 7870 graphics. For the most part, the Intel-plus-AMD gives better results. The one exception is DiRT Showdown at full detail with that GPU-bashing global illumination option enabled. Here, AMD-plus-AMD is up to 30 per cent faster. It's probably the difference between playable and not playable.
Like we said, it's difficult to be certain about what exactly is going on here. However, it does hint that there may be some truth in AMD's end-toend claims. Not the clinching argument then? Nope. But it does feed into a broader picture that looks far more positive for AMD than we were expecting.
