Product Reviews

When it comes to motherboards, SLI (Scalable Link Interface), allowing dual graphics cards for extra 3D performance, is the technology of the moment. Intel-based platforms supporting the feature are on their way, but for now only Athlon 64-based systems based on the nForce4 SLI chipset can perform this minor miracle. The first two standalone SLI motherboards to hit our test bench are the new top-of-the-line models from Gigabyte and MSI.

On both boards, between the two PCI Express graphics connector slots sits an unfamiliar socket, similar to a notebook's SODIMM memory connector. This contains a reversible circuit board: connected one way round you can use the first PCI Express graphics slot with a single graphics cards in non-SLI mode (any standard PCI Express card is supported, not just those from nVidia). Take it out and turn it round, and it literally rewires the board: the first graphics connector becomes an 8x slot, the second eight lanes being taken to the second connector. Pop in two SLI-enabled cards and gang them together with the supplied SLI connector - bridging the two cards at the top - and you're away. The VGA/DVI connector simply needs to be hooked up to the card in the first PCI Express slot, with the second card performing workhorse GPU duties. It isn't currently possible to use two cards in order to get four simultaneous displays running under Windows - the second card is there for 3D graphics-processing duties only. This might seem like a bit of waste, but the 2D video circuitry on modern cards represents a tiny fraction of the retail cost of the card; it's the 3D processing horsepower you're paying for.

One of the few drawbacks of nForce4 is the fact that the south bridge gets hot and requires active heatsinks. Both boards have fans clamped to the south bridge, moving fast and kicking out a lot of heat. The MSI's heat-generating voltage regulator transistors are also clamped to an elegant radiator-style silent heatsink, although the Gigabyte makes do without any extra heat dissipation on the main VRM. However, as with most higher-end Gigabyte boards, the K8NXP-SLI comes with an optional secondary voltage regulator daughterboard in the box. This plugs into a dedicated connector on the left-hand side of the board, converting the three-phase VRM circuitry to six-phase. This allegedly makes the board more stable and adds potential for overclocking, although none of our tests have ever shown any clear benefit from the device; it also has its own heatsink and fan, so won't improve acoustics.

As far as the backplane is concerned, the two boards differ only slightly. Both sport PS/2, serial, parallel,

ADVERTISEMENT

dual gigabit Ethernet and a bank of four USB 2 connectors. However, the Gigabyte has both digital coaxial output and, unusually, input connectors - useful if you're planning on using the board for high-level audio work. The MSI loses the coaxial input in favour of a FireWire port. The right-hand bank of analog audio jack connectors of the MSI sports an optical S/PDIF output, whereas the same space on the Gigabyte is occupied by an analog line-in jack socket.

As usual for modern boards, both come with extra ports on PCI blanking plates. The Gigabyte gives you a pair of extra USB ports on one and yet another pair plus FireWire 400 and 800 connectors on a second. The MSI comes replete with an extra pair of USB 2 connectors plus a pair of FireWire ports. The Gigabyte has a final ace up its sleeve, though, in the form of a bundled PCI 802.11b/g wireless network adaptor - an excellent inclusion given the price. You may be swayed by the fact that the MSI's onboard audio is a Creative Sound Blaster Live! 7.1-channel chip - the first time we've seen Sound Blaster-branded audio integrated into a board. It's an attractive feature that guarantees a level of compatibility, but you're unlikely to have problems with the Gigabyte's less auspicious, but nonetheless capable, 7.1 Realtek ALC850 codec.

Each board contains two rows of SATA connectors; four SATA II channels apiece from the nForce4 chipset (allowing a maximum transfer rate of 3Gb/sec), plus extra headers from external chipsets. The MSI has two extra SATA II channels; the Gigabyte has four extra, but these are SATA I, giving a maximum transfer rate of 1.5Gb/sec and no support for NCQ (native command queuing). It's not a huge limitation, given that modern disks are still some way from hitting the limits of a 1.5Gb/sec bandwidth. Both have four DDR DIMM sockets for a maximum of 4GB of RAM. The MSI has three extra conventional PCI slots, whereas the Gigabyte offers two conventional plus two single-lane PCI Express connectors - good for the future, but we've still yet to actually see any single-lane PCI Express devices.

When it comes to performance, the identical chipset on each board means we weren't expecting any huge differences between them. In fact, the relative performance difference is only just above the bounds of experimental error: the MSI's score of 2.59 is pipped by the Gigabyte's 2.63, but that's a difference of less than 2 per cent.

It's worth noting that a single graphics card actually works fine in both 8x/8x SLI and 16x non-SLI modes: the 3D benchmarks for a single card are identical in either mode. 8x PCI Express, which is roughly equivalent in performance to 8x AGP, clearly has bandwidth to spare, showing that 16x has loads of future-proofing built in.

These two boards are close when it comes to an overall verdict on which you should buy - both are very capable and packed with features. However, with its extra PCI Express slots, bundled wireless adaptor and marginally better overall performance, coupled with a difference in price of only a few pounds, the Gigabyte wins out. But whether or not an SLI board is the best choice for you depends on your current setup and upgrade plans: see above for the verdict on SLI itself.