Asus' A8N32-SLI Deluxe is the first nForce4 SLI X16-based Athlon 64 motherboard to hit the market, and it's more than just a simple refresh of Asus' nForce4 SLI design. The A8N32-SLI is equipped with a swanky new heat pipe cooler that keeps its VRMs and chipset cool without making a sound. It's also loaded with extra peripherals and eight-phase power. Oh, and it overclocks like mad, too. Read on for more on NVIDIA's nForce4 SLI X16 chipset and Asus' excellent implementation in the A8N32-SLI Deluxe.

The specs
As usual, we'll get the ball rolling with a glance at the A8N32-SLI's spec sheet.

NVIDIA's older nForce4 chipsets are single-chip designs, but the nForce4 SLI X16 has traditional north and south bridge chips. The north bridge serves up 18 lanes of PCI Express, 16 of which are dedicated to the board's first x16 graphics slot. Secondary graphics cards hang off the south bridge, which provides 16 lanes of PCI-E connectivity for graphics and an additional four lanes for additional PCI-E slots and peripherals. With secondary graphics cards hanging off the south bridge, the nForce4 SLI X16's chip-to-chip interconnect is particularly important. NVIDIA uses a 16-bit, 1GHz HyperTransport link to connect the chipset's north and south bridge components, yielding as much bandwidth (8GB/s) between the north and south bridge chips as the chipset has between itself and the Athlon 64 processor.

As it turns out, the speed of the nForce4 SLI X16's link to the CPU may help us predict whether the chipset's additional PCI Express lanes will help SLI performance. Increasing the number of PCI Express lanes allocated to each graphics card from eight to 16 boosts available graphics bandwidth from 2GB/s to 4GB/s in each direction, going to and from the graphics card. However, the nForce4 SLI X16's HyperTransport processor link only offers 4GB/s of bandwidth in each direction, so it can only fully saturate one 16-lane graphics slot at a time.

Of course, secondary graphics cards will also have to compete for interconnect bandwidth with the nForce4 SLI X16 south bridge's other features, including its ActiveArmor-accelerated Gigabit Ethernet and RAID. NVIDIA's RAID controller is perhaps the more impressive of these two features, as it's capable of spanning multiple arrays across both ATA and Serial ATA drives. Support for RAID 5 arrays has also been added to the storage controller's arsenal, a feature that has previously only been available on the company's Intel Edition chipsets. As one might expect, the nForce4 SLI X16 chipset retains support for 300MB/s Serial ATA transfer rates, as well.

Asus also equips the board with secondary GigE and SATA RAID controllers. The auxiliary Gigabit Ethernet option may come in handy for those leery of NVIDIA's GigE implementation, and the extra SATA ports can be useful for reasons we'll elaborate on in a moment. Both chips use PCI Express, leaving a Texas Instruments Firewire chip as the only device on the motherboard's PCI bus.

While the nForce4 SLI X16 chipset represents a refinement of previous nForce4 designs, it doesn't address the chipset's greatest weakness: its basic AC'97 audio controller. Not that we expect the world, but new high-end chipsets should at least support high-definition audio. Instead, the A8N32-SLI is stuck with AC'97 and a Realtek ALC850 codec. Hail to the crab, baby.