Motherboards Group Test

Hybrid Graphics
If you’re looking for a motherboard with an integrated GPU, one phrase you’re likely to encounter is ‘hybrid graphics’. Until recently, you had to make a straight choice between using the integrated graphics processor (IGP) or a discrete graphics card. Within the past six months, though, both AMD and Nvidia have started shipping chipsets that can combine the strengths of both GPUs – hence, hybrid graphics.

There are two distinct ways to take advantage of hybrid graphics. The first is a system Nvidia calls HybridPower. The idea is simple: when you’re working in Windows, or doing some other task that doesn’t need the full grunt of a separate graphics card, the card is powered down and the low-power onboard graphics chip is used instead. When you launch a game, the card is dynamically woken up to take over 3D graphics processing. Whichever GPU is doing the work, the chipset routes the signal to the right socket, so you don’t need to switch cables around.

Since a high-end graphics card can draw more than 100W even when idle, this system can save a lot of power without any cost in performance. AMD has a similar system, which it calls PowerXpress, but for now it’s only available on laptop chipsets.

The second aspect of hybrid graphics is a system called either Hybrid CrossFire or GeForce Boost, depending on which camp you’re in. This lets you combine the 3D processing power of the onboard GPU and a compatible discrete card in the same way as standard CrossFire/SLI.

We tried this system out with the Hybrid CrossFire-equipped Gigabyte GA-MA78GM-S2H. Running our Crysis benchmarks with the integrated Radeon HD 3200 GPU, we achieved an average frame rate of 17fps at 1024 x 768 with low detail. Turning detail up to medium slashed that to 8fps. With a discrete Radeon HD 3450, frame rates rose to 25 and 11fps respectively. Enabling Hybrid CrossFire nudged scores up just a tiny bit further to 27 and 12fps. We’ve seen before that 3D games simply don’t scale well across multiple GPUs, and it seems that’s especially true when one of the GPUs is a lightweight IGP.

The theory behind hybrid graphics is a good one, and Hybrid Power is a great way to save energy. But, based on our Crysis tests, we’d have to say Hybrid CrossFire is an idea ahead of its time, and not one we’d recommend basing a purchasing decision on.

Chipsets: A bridge too far?
This month, we’ve focused on each motherboard’s capabilities and features. But to an extent these are a function of the chipset on which the board is based.
The chipset consists of two separate controllers, known as a north bridge and a south bridge. The north bridge handles communications between the high-bandwidth parts of a PC; typically, the processor, system RAM and graphics card slot.
It also connects directly with the south bridge, which handles less demanding components, such as USB ports, SATA controllers, ethernet and any old-style PCI slots. Some south bridges include integrated graphics, too.

The efficiency of the chipset can affect the performance of the entire system (as you can see in the graph on page 56), and its capabilities dictate which components the motherboard can support. For example, an older chipset may be unable to run a brand-new processor at full speed. And you won’t be able to use multiple graphics cards unless your north bridge is specifically designed to handle that.

There are three major chipset manufacturers: AMD, Intel and Nvidia. Not surprisingly, AMD’s current offerings are all designed to work with AMD’s own processors. You’ll still see boards based on the old 690 chipset, but the current range is the 7 series, which comprises the 740, 770, 780 and 790, plus a few variants, which are indicated by a suffixed letter.

At the bottom of the range, the 740 supports just a single PCI-E 16x slot, and a maximum HyperTransport frequency of 800MHz. The top-end 790FX, meanwhile, can handle four ATi graphics cards at once (two at PCI-E 16x speed, two at 8x) and supports HyperTransport speeds up to 2.6GHz.

Intel’s chipsets likewise support only Intel processors. Intel offers a wider range of chipsets than AMD, but on a modern motherboard you’re most likely to see the P35, X38 and X48. The P35 is a good all-rounder, supporting all recent Intel processors with its 1333MHz front side bus and accepting both DDR2 and DDR3 memory, although motherboard manufacturers generally implement only one or the other. It’s limited to just one PCI-E 16x slot, though: if you want a second slot, you’ll need to move up to the X38 chipset, which also adds support for ATi’s CrossFire X system (despite the fact that ATi is now owned by Intel’s competitor, AMD).

Finally, the X48 lets you overclock both the RAM and front side bus up to 1.6GHz and promises future support for 10 Gigabit ethernet, although that has yet to appear on the market.

The third major player, Nvidia, makes chipsets for both AMD and Intel processors. The current range for AMD CPUs is pretty small, though, extending only to the nForce 720a and nForce 730a, and the only difference between the two is that the 730a has a more powerful integrated graphics chip. More powerful chipsets are expected soon that will add three-way SLI and faster memory support.

On the Intel side, Nvidia’s older 600 series motherboards are still popular – there are two in this month’s Labs – while the current range consists of the 750i, 780i, 790i and 790i Ultra. Features improve as you go up the range, maxing out with the 790i Ultra – as seen this month in the Asus Striker II Extreme – which will drive up to four GPUs at once.

For most purposes, you can get by without worrying too much about which chipset a motherboard uses: after all, it’s the features that are important rather than the chips themselves. However, as we’ve seen, the chipset does have a small effect on system performance. And if you have an eye on future upgrade possibilities, a newer chipset is more likely to work with as-yet unreleased hardware than will one that’s already approaching the end of its life.

This Group Test appeared in the August, 2008 issue of PC & Tech Authority Magazine