nForce Rehash and 3-Way SLI

The PC component scene over the past year was mostly dominated with Intel news, Intel processors, Intel chipsets and Intel technology. However, if you would have remembered back in 2006, the Intel desktop scene was shared with NVIDIA. The nForce 680i SLI chipset was perhaps the most technology-packed core logic chipset to hit the market for the Intel platform. The nForce 680i SLI brought firsts in dual full speed x16 graphics lanes, built-in Gigabit network teaming/packet prioritization and NVIDIA's SLI Memory technology. It also packed support for 1333MHz FSB and DDR2 speeds up to 1200MHz (with SLI Memory). By all means, NVIDIA had a chipset on their hands that was more advanced than its time. But it was also the most expensive chipset to implement.

In the year that has passed though, the market has caught up with NVIDIA. On one hand, NVIDIA may have been content that the nForce 680i SLI was weathering the processor changes that have come its way, but with DDR3 and PCI Express 2.0 making their debut, it was clear indicator that the market has moved on. In what has seemed like an eternity in the lifespan of a chipset, NVIDIA launched the nForce 700i series of chipsets late last year, with the nForce 780i SLI as the successor to the nForce 680i SLI. This however, isn't as exciting as it seems, because the nForce 780i SLI is really an old friend in disguise. While it does have a new bag of tricks up its sleeve, the real successor to the nForce 680i SLI is the nForce 790i SLI, which is still in the making.

So, for those that require their nForce fix, you'll have to be content with the nForce 780i SLI for now. So, let us take a very quick look at the nForce 780i SLI chipset. On paper, the major improvements of the nForce 780i SLI over the nForce 680i SLI include: More PCI Express lanes, PCI Express 2.0, 3-Way SLI and NVIDIA ESA. You might have read that the nForce 780i SLI also adds Penryn support. However, the nForce 680i SLI technically supports these CPUs, but the difference in motherboard circuitry requirements would have meant compatibility issues with older motherboards, regardless of core logic level support. Penryn aside, the older nForce 680i SLI had compatibility problems with quad-core processors in general. So in a way, it's about time the nForce 780i SLI arrived to offer an updated platform.

NVIDIA nForce 780i SLI chipset block diagram. Source: NVIDIA.

In reality, the nForce 780i SLI is nothing more than a re-branded nForce 680i SLI; That being the SPP and MCP chips are essentially the same ones used for the nForce 680i SLI. However, if you look at the block diagram above, you'll notice the real difference. Instead of a traditional Northbridge-Southbridge link, there is a third chip in the picture connected to the SPP. This third chip is the nForce 200, which is the real reason the nForce 780i SLI has PCI Express 2.0 support.

The nForce 780i SLI SPP is essentially the same as the nForce 680i SLI with a tweaked PCIe x16 link.

nForce 570 SLI chip reused for the MCP...again.

The nForce 200 offers up 32 PCI Express 2.0 lanes, which is used to provide dual x16 PCIe 2.0 SLI support on nForce 780i SLI motherboards. The chip itself is linked to the SPP through a proprietary interconnect. This is not detailed in the block diagram above, but if you recall, the nForce 680i SLI SPP has (or had) support for one PCI Express 1.0 x16 link. This link has now been tweaked (in other words overclocked) to provide the interconnect between the nForce 780i SLI SPP and the nForce 200. However, if you do the math, the nForce 200 is able to provide up to 32GB/s of graphics bandwidth to two PCIe 2.0 graphics cards. The SPP<->nForce 200 link however, is a mere 14.4GB/s. Not really an ideal, nor optimal situation when it comes to crunch time, but luckily for us, today's GPUs and applications haven't yet to bottleneck PCI Express bandwidth. Also, data in SLI mode is mostly transported between cards via the SLI Bridge cable, and not much of it goes through the chipset. Because of this, NVIDIA claims that there is no compromise in performance between the nForce 780i SLI solution and its current competitors.

The nForce 200 is the new member to the chipset providing 32 lanes of PCI Express 2.0.

3-Way SLI is also supported on the nForce 780i SLI, but while the third slot is a full speed PCIe x16 slot, it is provided by the MCP chip, which is only PCI Express 1.0 compliant.

So as you can see, the nForce 780i SLI is really a band-aid solution by NVIDIA to update their current offering with a product that can support PCIe 2.0 and their 3-Way SLI configuration before the nForce 790i SLI arrives, which will be the true chipset successor with native 1600MHz FSB, PCI Express 2.0 and DDR3 support on the SPP itself. While that's definitely a story for another time (perhaps late next month), today we bring you a review of a mainstream nForce 780i SLI motherboard from ASUS. So read on to find out our thoughts.