Gigabyte GA-8N-SLI Quad Royal review
If we had to name the one most significant technology trend during 2005, it would be increased parallelism. Dual-core CPUs and hugely parallel graphics cards stole many of the performance headlines, while dual-card SLI (Scalable Link Interface) went mainstream and ATi launched its response with CrossFire; two was the magic number for 2005. But this year, the industry looks set to skip three and move straight onto four, with Gigabyte already managing to shoehorn four PCI Express graphics slots onto this dual-core-capable motherboard.
How the Gigabyte engineers have managed this is surprisingly straightforward, on paper at least – they’ve combined the architectures from both AMD and Intel versions of nVidia’s nForce4 chipset. The nForce4 SLI Intel Edition north bridge attaches to an AMD south bridge using the same HyperTransport bus that the AMD version uses to talk to an Athlon 64. So Gigabyte has paired these two apparently disparate north and south bridge chips together using this common interface. And, as both chips are SLI versions, each can provide two PCI Express graphics slots.
But before you rush out to buy a Quad Royal, jam in four 7800 GTX 512s and post the highest 3D scores ever, note that you can’t actually use SLI over four slots. The first hurdle to overcome is for nVidia to actually release drivers that address more than two GPUs. There’s no technical reason why SLI can’t scale up to four GPUs or more, but two high-end cards are enough to play the newest games at their best for at least a year, so it’s unlikely it will be a high priority for either consumers or developers.
The second hurdle is that SLI bridge connectors link only two cards. This dedicated high-speed data link is the only way to shift the huge amounts of data from one GPU straight into another at acceptable speeds. The 2GB/sec HyperTransport link struggles to relay the information between two cards quickly enough now, let alone split a render load four ways to allow each GPU to communicate with any other.
It’s actually feeding an array of monitors that’s the point of this motherboard, and with four cards settled in the four slots it will give you eight monitors easily enough. And then there’s the PCI slot that could conceivably take a legacy graphics card, squeezed between slots three and four. That’s a maximum ten-screen array, gratuitous for even complex video-editing or music-creation facilities.
SLI is still viable, providing you can live with keeping it to only six screens. Use the second slot for a low-cost, dual-output card and SLI your gaming cards over the AMD chipset-governed third and fourth slots. This is the only configuration that will allow for switching between an extended Desktop and SLI without having to remove cards. The BIOS won’t let you send data to the first slot if the third and fourth share bandwidth for SLI, and SLI won’t work if a graphics card is sitting in the first slot, regardless of whether it’s actually doing anything.
We used an XFX 6600 GT for basic dual output (a much cheaper 6200 TC would work just as well) and PNY kindly loaned us two 7800 GTXs for slots three and four. When you want to switch from your massive Desktop to work in SLI, it’s then a case of turning on SLI multi-GPU rendering in the graphics driver. The monitors fed by the slave SLI card will then turn off as it devotes itself to the master card. You’ll need to ensure that the monitor on which you play games is fed by the primary output of the master SLI card too, and that it’s set as your primary monitor in Windows.