Intel Skulltrail and Multi-GPU Graphics: Mixed Results

Manufacturer: Intel

Come on Guys

Today some rather interesting information has been passing through our
Inbox on the status of Intel's Skulltrail platform and the
currently available multi-GPU solutions.  In case you haven't been following the life of Intel's Skulltrail platform, it is Intel's "answer" to the failed AMD QuadFX platform from a year ago.  It will be available later in the month, but details about the technology have not been hard to come by

A custom built enterprise-class motherboard is the backbone of
Skulltrail and is powered by both the Intel 5400 north bridge and a
pair of NVIDIA nForce 100 chips to enable four PCI Express 1.0 x16 slot
support.  Two LGA771 processor sockets require either Xeon processors
or the upcoming QX9775 processors (3.20 GHz, 1600 MHz FSB) so using standard Core 2 Duo processors is out of the question.  Intel is promoting this technology as the
ultimate in gaming platforms, and it's hard to dispute that when
looking at the specifications alone.

Intel Skulltrail motherboard

Perhaps the most appealing part of Skulltrail is that it was revealed it would support NVIDIA SLI technology - the first non-NVIDIA chipset motherboard to do so.  That is the
power of NVIDIA's nForce 100 chips - basically PCI Express bridges with
custom NVIDIA logic in them to accommodate SLI configurations.  And with
the recent release of NVIDIA's 3-Way SLI technology,
we were really looking forward to pairing Skulltrail's 8-cores of
processing power with 3-Way SLI to overcome any potential bottlenecks
for PC gaming.  Apparently that will not be an option though.

Many views, one problem

In my talks with Intel about Skulltrail, I got this information
this week when probing their PR and engineering team about potential
Skulltrail configurations, specifically on 3-Way SLI:

Mechanically and electrically, with 4 PCIe slots, Skulltrail can support up to 4 graphics cards.  Drivers and validation and are up to the graphics card vendors as always.

This is a somewhat familiar argument.  Remember when VIA was struggling with NVIDIA's stranglehold on SLI technology in the chipset department?  They had the same claim: we are completely capable of running SLI graphics solutions if NVIDIA will enable it in the driver.  That didn't happen,
NVIDIA kept SLI technology all to itself, and eventually VIA's
enthusiast products dried up.  That obviously isn't going to happen to
Intel's chipset department, but 3-Way SLI and standard SLI are
apparently very different in the eyes of NVIDIA:

wanted to inform you that Skulltrail motherboards use two NVIDIA nForce
100 SLI MCPs. The nForce 100 SLI chip allows a maximum of two GeForce
graphics cards to work together, enabling SLI between two GeForce GPUs
such as the GeForce 8800 GTX, and enables Quad SLI on dual-GPU graphics
boards such as the GeForce 7950 GX2.

The nForce 100 SLI MCP will NOT support 3-way SLI. This cannot change even with a driver/bios update.

As it would seem, Intel's Skulltrail platform is NOT electrically
compatible with 3-Way SLI technology and it will never be able to
properly run three NVIDIA graphics cards for performance enhancements. 
Obviously this is the same answer that NVIDIA gave in regards to supporting SLI on VIA chipsets, AMD chipsets or anything
else.  At one point I was able to test SLI on a VIA chipset
motherboard, many moons ago, but nothing was ever available to the end user to allow

Diagram of NVIDIA's proprietary Broadcast and PW Short patents - more here

Though I don't have verification from NVIDIA on this, I am guessing that if probed for more detail, they will point to their nForce 200 chip as being the solution available for 3-Way SLI.  At CES this past January NVIDIA finally revealed some information on patents they filed for technologies used on their chipsets to allow for better multi-GPU scaling: namely posted writes and broadcast.  These two technologies, as we detailed in our CES coverage, allow NVIDIA to by-pass the CPU for some critical data duplication and in theory improve efficiency.  The nForce 200 chip is used on nForce 780i motherboards as well as the upcoming 780a motherboards but there is just one problem:

The nForce 680i motherboards do NOT have an nForce 200 chip on them yet are approved for 3-Way SLI support.  Our first 3-Way SLI system that NVIDIA provided was built around an EVGA 680i motherboard and thus I have to assume that 3-Way SLI should be functional on other chipsets with three PCIe x16 slots.

Nuh-uh!  Yes-huh!

Most likely, we will never get a real answer on situations like
this or even this specific case.  It's like a
multi-billion-dollar-company version of he-said-she-said and should
have the same result: a stalemate.  Is
there a true specific hardware issue that prevents 3-Way SLI from
functioning on Skulltrail motherboards, or is the hardware function
NVIDIA speaks of simply a proprietary performance enhancement?
  Both sides will probably argue their cases until they are blue in the face.

The only thing I do know is that the loser here is the enthusiast. 
Users looking to make the purchase of an expensive Skulltrail system
will have to scratch 3-Way SLI off of their potential build sheet.

Quad HD 3870s, though not shown in a Skulltrail motherboard

On the completely opposite side of all this, I had some contact
with AMD regarding their plans for Skulltrail and CrossFire support. 
As it turns out, AMD is planning to support two-card, three-card and
four-card CrossFireX solutions (they are already been demonstrated as working in fact) on Intel's new gaming platform.  AMD/ATI
has been supporting CrossFire on Intel, NVIDIA and of course their own
chipsets since the outset of its launch and their commitment to the idea of an open-platform looks to continue
even when their technology falls into the hands of their competitor in
the CPU market.   Some might call it a position of necessity; either
way the enthusiast wins. 

We'll have more on Intel's Skulltrail very soon and we'll analyze
this information even in more detail at that time.  For now, take this
information and digest it how you will.

Join us in the PCPer Video Card forums to questions and comments on this editorial!


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