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Intel Skulltrail Platform Review - Eight Cores, SLI and CrossFire

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Subject: Motherboards
Manufacturer: Intel
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Intel Skulltrail Platform

Introduction

Intel's Skulltrail platform has lead a very public and outspoken, yet short, life.  Our first official coverage of Intel's Skulltrail platform came in April of 2007 at Spring IDF though rumors had been swirling about it for some time before that.  At nearly every occasion, Intel was promoting and showing off what they thought was the ultimate enthusiast platform to the media. 

Skulltrail first began rumbling when AMD started to showcase its "ultimate enthusiast" platform, QuadFX.  It paired a set of re-branded dual-core Opteron processors with NVIDIA workstation class motherboard with a brand new chipset.  They intended for QuadFX to compete with the Intel quad-core processors that were available able the time, but even those closest inside AMD will be able to tell you this wasn't a major flop on their part.  It was hot, consumed too much power, was too expensive and couldn't perform better than CPUs from Intel available on a cheaper platform. 

When QuadFX took the dive, many people, including myself, thought we might not actually see Intel's Skulltrail platform but I was wrong and today we have a full review of the platform's technology and performance.

What is Skulltrail?

Skulltrail is targeted at being the ultimate enthusiast platform, but what does that mean?  It seems either Intel, NVIDIA or AMD is touting that label every other month; in this case Intel can actually make a claim for it legitimately.  The Skulltrail platform differs from your traditional enthusiast systems by offering support for two Intel Core architecture processors, an eATX motherboard with four PCIe x16 slots, FB-DIMM memory technology and being the first non-NVIDIA chipset motherboard to offer SLI support. 

It all starts really with the new, custom built Intel Skulltrail motherboard shown below.



Click to Enlarge
The motherboard is obviously larger than your standard enthusiast motherboard and is built to the eATX (extended ATX) specifications common in the server and workstation markets.  You can clearly see the dual processor sockets and PCIe x16 slots among the other features on the board.

We'll step through all the features with some images below.

The secondary CPU socket is shown here cradling a quad-core Core 2 Extreme QX9775 processor, half of the eight cores on our system.  You can see the main ATX power connection on the left here as well as the various power conditioning components surrounding the CPU.  Interestingly, and somewhat disappointingly, the area here is kind of cramped.  Even the Zalman fans that Intel sent along with the test system had trouble being squeezed in for installation.

The primary CPU socket is the same as the secondary with the same spacing problems. 

The Intel 5400 north bridge will probably be new to most readers - it's a workstation chipset that features an FB-DIMM DDR2 memory controller that you won't find on any standard desktop products.  Besides the memory controller the Intel 5400 MCH also is responsible for the primary PCI Express 1.0 x16 slots that we'll touch more on later. 

The two 8-pin eATX power connections are shown here on the left as well - many power supplies will not have TWO of these available so potential Skulltrail users should check before hand or look into one of the many 1kW+ units we have reviewed recently

The Intel ESB2 (enterprise south bridge) chip and pair of NVIDIA nForce 100 chips reside under this large, and pretty loud, heatsink fan combo.  It is low profile and thus won't interfere with any kinds of graphics cards installations.

Hidden underneath that heatsink are these three chips - the two on the left are the ones that give the Skulltrail motherboard its SLI capability. 

Effectively, the nForce 100 chip is a PCI Express bridge chip with some custom logic in it to support SLI graphics.  It takes in a single x16 PCIe 1.0 connection, provided by the Intel 5400 MCH, and splits that into two full speed PCIe x16 connections.  Those slots are then capable of running pairs of graphics cards, NVIDIA or AMD, and function as you would normally expect.  These nF100 chips were the precursor to the nForce 200 chips that reside on the nForce 780i and upcoming nForce 780a chipsets. 

There are two of these on the Skulltrail board - each gets its own x16 PCIe connection from the north bridge and each creates two x16 PCIe slots of its own.  That gives the motherboard a total of four full speed x16 PCI Express graphics slots - a first.

The memory support on the Skulltrail motherboard differs a bit from what you might expect.  Since the board is based on a workstation/server design and has support for dual-processor technology, FB-DIMM DDR2 memory is required.  The move to DDR2 isn't that big a disadvantage, as we have seen the P35 motherboards use either DDR2 or DDR3 with minimal performances at stock speeds, but the fully buffered portion of it does add some dead weight.  Because of the absolute stability and reliability required with servers and workstations, FB-DIMMs substitute the raw speed seen on other desktop boards for that reliability.  Because of that, raw memory performance is going to be lower than normal - we'll show in our benchmarks later in the review. 

The expansion options on the Skulltrail motherboard are pretty substantial!  The four blue PCIe x16 slots are each a full x16 bandwidth and of course can support other cards besides GPUs should you have them to use.  There are two legacy PCI slots provided by the ESB2 south bridge, though they are oddly placed in my view.  Because Intel recommends using the closest two (in relation to the memory and CPUs) PCIe slots for SLI or CrossFire when only two GPUs are used, both PCI slots could be useless if you have dual-slot cooled cards.  If you have a PCI sound card for example, you are going to be stuck using the first and third PCIe slots - but you just CAN NOT do that with AMD CrossFire configurations:

The CrossFire cables, since the very beginning of CrossFire technology, are too short to make the jump from the first to third slots on Intel's Skulltrail motherboard. 
This basically means that CrossFire users, as long as we are talking about dual-slot cooled cards, will be PCI-less on Skulltrail. 

Moving on down the board, we find the six SATA connections that support Intel Matrix RAID technology along with a single legacy IDE channel - something that the ICH9 no longer offers but remains on the ESB2 south bridge.  A standard LED POST display is included on the board as well for help in troubleshooting. 

At the rear panel on the motherboard you might be surprised to find there are no legacy connections: no PS2, no serial, parallel or anything like that.  In fact the only analog connections are the 8-channel audio outputs from the Azalia HD audio connection.  There is a single Gigabit NIC, six USB 2.0 connections and a pair of eSATA connections for external storage options. 

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