PCs are phenomenally flexible, configurable devices. That’s kinda why we love ‘em so much. But there are limits to what you can achieve. And most of those are defined by your choice of motherboard, all of which means clarity of purpose is paramount. Identify what you want from your PC and make sure you have a motherboard to match.

This month we’ve selected a trio of motherboard pairings to suit three popular usage models: small-form factor systems with HTPC capability, overclocking rigs and high-end multi-GPU gaming monsters.

Before we come to the boards in question, what of the seminal AMD or Intel question? Actually, at the moment it’s often not much of a quandary thanks to the feebleness of most of AMD’s processor product range. We’ve said it before, but it’s seriously bad news for the entire PC industry to have AMD struggling to keep Intel honest.

If the much needed 45nm die shrink of the AMD Phenom family of processors doesn’t close the gap significantly, expect to see Intel push up the prices. For now, if performance is a priority, AMD chips are frankly uncompetitive, even at the more affordable end of the spectrum. But throw issues such as power consumption, form factor and HTPC considerations into the mix and it’s a very different story.

For the HTPC-centric category, we’ve therefore turned to a pair of brand new AMD-compatible boards with the latest and most sophisticated integrated chipsets, the GeForce 8200M from NVIDIA and AMD’s 780G. If there’s an Intel-powered alternative that comes close to these two for small-form factor media PC prowess, we’ve yet to see it.

Palit’s N78S and the Gigabyte GA-MA780GM-S2H are both micro-ATX boards with all passive cooling and fancy new DirextX 10 capable integrated CPUs. Indeed, they both represent our first taste of a new take on multi-GPU graphics rendering from NVIDIA and AMD, dubbed ‘Hybrid SLI’ and ‘Hybrid CrossFire’ respectively.

The basic idea behind both is the pairing up of the motherboard’s integrated GPU with a discrete graphics card. But the details diverge enough to make them substantially different propositions.

Pairing Up

Both solutions allow users to boost the performance of an add-in graphics card by running it in multi-GPU mode with the integrated graphics chip. According to claims from both NVIDIA and AMD, the result is a big boost in performance for low-end graphics cards. In practice, it’s an overly complex and inefficient way of achieving barely acceptable 3D performance, but more on that later. Hybrid CrossFire’s abilities more or less end there. The more attractive of the two by far is Hybrid SLI, represented by Palit’s N78S and its NVIDIA GeForce 8200M chipset. That’s because Hybrid SLI cap also act as a power-saving measure for high performance PCs. In this scenario, users can switch between a powerful but noisy and glutinous graphics board and the onboard integrated GPU from within Windows.

There’s no need to reboot or swap monitor cables around. Connect your monitor to the motherboard’s video-out port and allow the NVIDIA driver software to do the rest. That includes completely powering down the add-in GPU and its cooling fan. Clever, eh? Hybrid graphics with DirectX 10 support isn’t the only common feature. These boards also share the honor of sporting the first integrated chipsets to boast full hardware acceleration of all three of the important video codecs, VC-1, AVC and MPEG2. In both cases, this comes courtesy of the latest 2D video engines from NVIDIA and AMD, known as PureVideo HD and UVD. That’s precisely what you need, of course, to guarantee smooth playback of full 1080p Blu-ray discs.

Home HD Motherboards

If these two home cinema-centric boards are remarkably similar, there’s also not much between the P35 pairing we’ve selected for the overclocking showdown. The fact is, Intel’s P35 remains the weapon of choice, if it’s pure CPU speed you’re seeking. Remarkably, that remains the case even with the arrival of NVIDIA’s swanky new 790i, a chipset we suspected might just topple the P35 chipset from its position of king of the overclockers.

It’s not uncommon to see P35 hit bus speeds in excess of 500MHz without the need for hit and miss tweaking of northbridge voltages. Even Intel’s latest X48 chipset typically tends to run out of puff around 475MHz. In that context, attention to detail and execution will separate MSI P35 Platinum from Asus’s trusty P5K3 Deluxe.

But what of high-end motherboard design to form the basis of multi-GPU performance PCs? Until recently, the pickings were a bit thin. Intel’s X38 and X48 chipsets are fine things indeed, in terms of performance. But thanks to NVIDIA’s decision to lock SLI technology down to its own chipsets (unnecessarily in our view), the X38 and X48 only support AMD’s competing CrossFire platform. That meant SLI fans were forced to go with the somewhat substandard NVIDIA 680i or 780i option. But not anymore. NVIDIA is back on form with the 790i. It will be an extremely tight contest for top honors. If that’s the theory behind all these boards, how do they perform in the silicon?

Perhaps the most intriguing motherboards here are the AMD-compatible micro-ATX pair. In concert with a low voltage dual-core Athlon 64 processor they deliver truly spectacular power efficiency. Both of the boards are within spitting distance of 100 watts running at full CPU load and idle around the 50 watt mark.

That’s for a full system with 2GB of RAM, hard disk and optical drive. That represents as little as a quarter of the consumption of a high-end quad-core rig. It also translates into extremely unobtrusive operation that’s a perfect match for a home cinema installation Less impressive is the performance of its much-touted DX10 integrated GPUs, in 3D mode at least. Neither are capable of anything remotely resembling a pleasant gaming experience. And frankly neither pack enough grunt to make the Hybrid dual-GPU option at all attractive.

Where things get more interesting is the contest for home cinema prowess. And that must go to the Gigabyte thanks to its HDMI port and fully driver-supported 2D acceleration core. Add in a low-voltage AMD Athlon 64 X2 dual-core processor and you have a motherboard and CPU combo with full HD capabilities for just $l80.

As for the P35 overclocker’s boards, it is mostly one-way traffic. A result of 520MHz is an impressive bus speed to hit for any Intel-compatible motherboard. The fact that the Asus P5K3 Deluxe can achieve it without any voltage tweaks makes for an extremely user-friendly overclocking platform. You can be confident you’ll get the most out of any CPU with this motherboard.

Our only doubt involves the fact that it’s a DDR3 motherboard. In theory the higher clockspeeds of DDR3 memory should be a boon for overclocking. In practice, a pair of quality DD2 memory DIMMs do the job just tine. Factor in the current utterly ludicrous price of DDR3 memory sticks and the benefits just don’t add up.

Performance per Pound

All of which just leaves just the big ticket X48 and 790i pairing from MSI and Asus respectively. There’s no doubting the all new Striker II Extreme from Asus is a sickeningly desirable thing. Everything from its feature-packed BIOS, to the hardware power and reset buttons and the northbridge heatsink pre-plumbed for water cooling, reek of quality, class and most of all expense.

The 790i chipset also brings NVIDIA’s SLI platform bang up to date with DDR3 and proper PCI Express support, as well as decent overclocking headroom. As good as it is, however, it simply cannot be worth nearly $450. Particularly when it offers less overclocking oomph than Asus’s own sub-$l50 Intel P35 board. The performance advantage of the 790i chipset is far too slender to make any real world difference, too.

The spoils must therefore go to MSI’s X48 platinum. It’s a lean, mean enthusiast board at a sensible price. Yes, it does lock you into AMD’s CrossFire platform in terms of multi-GPU support. But until NVIDIA puts the interests of buyers ahead of its own selfish desires to maximize revenues from SLI chipsets, the perfect multi-GPU platform simply isn’t possible.