NVIDIA's Multi-GPU Technology - SLI, it's baaack!

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Boards and Configurations

So, it looks like NVIDIA has been a bit more focused on "out of the box" thinking as of late, since obviously this new Multi-GPU parallel rendering technique would be nearly impossible without the availability of the new PCI Express interface for graphics.  With its serial point to point communications protocol, dedicated links back to system resources and gobs of available managed bandwidth, PCI Express is a natural for these types of applications.


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Obviously, there's a very different motherboard technology that is key to the architecture.  Dual X16 PCI Express Graphics slots will also be required for this type of configuration.  Above you'll see a motherboard from SuperMicro based on what we think is Intel's forthcoming E7515 "Tumwater" chipset for Intel's new "Nacona" Xeon workstation processor that also has 64-bit extensions ready to rumble.  We did not get conformation on this from NVIDIA but the timing of their announcement, along with Intel's today, suggests this.

The question is, will we see other chipset and motherboard permutations moving forward, that have the all-important dual PCI Express X16 graphics slots?  You could also conceive that an i925X solution with an add on discrete X16 switch, could be a possibility.  Consumer class singe-CPU Tumwater boards could also be released.  And NVIDIA's next itineration of the nForce will almost definitely support multiple PCI Express X16 slots. However again, until we get more firm details, we're simply speculating here.  We'll come back and update this section as more information come forth from either NVIDIA or Intel.

Closer inspection of the a GeForce 6800 Ultra In SLI
So it is really SLI!


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Above you can see NVIDIA's new board to board connector for the PCI Express/NV45 versions of their GeForce 6800.  This is a simple rigid PCB with a female slot connector that mates on to the top edge connector of the graphics card.  NVIDIA informed us that SLI ready PCB designs will only be made available on higher end products like the GeForce 6800 GT and 6800 Ultra models.  Here's where NVIDIA is actually coining the acronym "SLI" again, which stands for Scalable Link Interface.

Historically, 3dfx cards used ribbon cables to connect master and slave cards together and pass through cables to send analog output from one card to the other.  However now with SLI, all data is transferred through this connector via the MIO (multi-function IO) port, a block of circuitry on the GPU itself that provides a communications link and chip level assist for load balancing.  It's a fully digital implementation, versus legacy SLI which performs a digital to analog conversion. This MIO port, in combination with NVIDIA load balancing algorithms, will supposedly allow perfect image fidelity, along with a claimed 1.87X average speed improvement. We'll be testing NVIDIA's new SLI in our labs in the coming weeks so stay tuned and we'll see if this claim rings true.

The dual card nature of and SLI configuration will also give users the ability to run a quad-monitor setup in "2D mode".  NVIDIA tells us there will be a switch in the drivers that will allow the SLI functionality to be disabled, which makes each card function independently of the other.

Tags:  Nvidia, Tech, GPU, sli, Technology, AAA, multi-GPU, aac, AA, ULT, AC, id, K

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