Motherboard Guide

NVIDIA nForce 790i Ultra SLI Chipset review

NVIDIA nForce 790i Ultra SLI Performance Review

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Chipset Level Features

nForce 790i Ultra SLI SPP

Unlike the nForce 780i SLI, the nForce 790i Ultra SLI will be a proper two part chipset with all the new enhancements built right into the SPP chipset itself. FSB support has been boosted to 1600MHz to meet Intel's updated standard and the Core 2 Extreme QX9770 (the only FSB1600 CPU out in the wild still). This makes the nForce 790i Ultra SLI the direct competitor of Intel's X48 chipset.

The nForce 790i Ultra SLI natively features 32 PCI Express 2.0 lanes that are configured for graphics in two PCIe x16 slots. The memory controller is designed to natively support DDR3 memory up to 2000MHz speeds. However, since the current JEDEC standards only extend to DDR3-1333, the official stance for the nForce 790i Ultra SLI is 1333MHz. To access higher memory speeds, NVIDIA makes use of their new EPP 2.0 standards. EPP 2.0 is essentially what NVIDIA is calling the DDR3 version of EPP or Enhanced Performance Profile, the superset of memory timings above the standard SPD data.

Memory modules supporting EPP 2.0 is practically guaranteed to operate at higher speeds and lower latencies of DDR3-1600, DDR3-1800 and even DDR3-2000. NVIDIA has made sure the EPP 2.0 memory will be available by the time nForce 790i Ultra SLI boards hit the stores and their partners have been busy getting themselves ready. Our reference nForce 790i Ultra SLI motherboard happens to come with a pair of Crucial BalistiX EPP 2.0 memory operating at DDR3-2000, which you can see in our performance benchmarks section later on.


nForce 790i Ultra SLI MCP

The nForce 790i Ultra SLI MCP on the other hand, doesn't look like it has been changed since the past few chipsets. From the specifications alone, we can surmise that it is the same nForce 570 chip, though this really isn't an issue as it has yet to outlive its features. As you can see from the block diagram below, the MCP offers two Gigabit LAN MACs with NVIDIA's DualNet and FirstPacket features, six SATA 3.0Gbps ports, continued support for PATA ports, ten USB 2.0, HD Audio and a ton of extra PCI Express lanes - 28 in total. The only complaint is that they are still based on the PCI Express 1.0 standards. Of course, NVIDIA's new ESA architecture standard is fully supported by the nForce 790i Ultra SLI.

Graphics and SLI

The NVIDIA nForce 790i Ultra SLI features 3-way SLI in a similar fashion as the nForce 780i SLI. The two primary PCIe x16 ports will come from the SPP while the third 'borrowed' from the MCP. By NVIDIA design, you should only find nForce 790i Ultra SLI motherboards with three PCIe x16 slots. In order to support quad SLI, you will actually have to use a pair of dual-core cards such as the GeForce 9800 GX2.

Beside physical SLI support, the nForce 790i Ultra SLI actually features some CPU<->chipset<->GPU communication enhancements to improve performance and reduce latency in multi-GPU configurations. The first is called PWShort (Post-Write Shortcut), which is a direct GPU-to-GPU link. Basically, with PWShort, the PCIe controller can now forward messages between GPUs without the need to parse them to the memory controller first.

The second feature is called Broadcast, which allows the CPU to only send one set of commands or graphics data (geometry, texture, etc.) to the GPU. In an SLI configuration, the chipset will automatically replicate the CPU commands and broadcast it parallel to all GPUs. Without Broadcast, the CPU often has to serially send out the same set of data to each GPU.