Intel D5400XS Desktop Board
As we see, Intel didn’t have to develop new processors for the Skulltrail platform. In fact, all the engineering work got down to putting new marking on the already existing Xeon X5482 CPUs. However, the same couldn’t be done for the mainboard that had to become the basis for the high-performance dual-socket desktop platform. I doubt hardware enthusiasts would like a server or workstation mainboard, they usually value different platform qualities.
Intel has already faced this problem when they introduced their V8 platform to the users. That system included a regular workstation board that didn’t really make the desired impression on the users, frankly speaking. Therefore, Intel learned its lesson and didn’t repeat the same mistake when working on the Skulltrail platform. The engineers had to design a specially adapted mainboard that was called Intel D5400XS Desktop Board.
However, it is important to understand that they didn’t have much room for creativity. Contemporary desktop chipsets targeted for top of the line systems do not support dual-socket configurations. That is why D5400XS was built on core logic set for servers and workstations called i5400B Express (codenamed Seaburg). This is today’s top Intel chipset supporting dual-socket systems working with 1600MHz bus. So, no wonder that Intel D5400XS Desktop Board supports not only Core 2 Extreme QX9775 processors, but is also compatible with the entire Xeon processor family targeted for dual-socket platforms. Taking into account that Core 2 Extreme QX9775 costs around $1500, it may be a very useful additional feature for the board.
Although i5400B Express chipset wasn’t initially designed for Skulltrail systems, is a very advanced solution in terms of supported features and functionality. In particular, one of its strengths is two independent processor busses with point-to-point topology serving to connect two CPUs within the same system. So, this chipset eliminates the bottleneck of previous-generation multi-processor systems on Xeon CPUs where all processors sat on the same bus.
Moreover, i5400B Express boasts one more feature that allows increasing the efficiency of communication between the CPUs and the memory. It features a special buffer called Snoop Filter containing the info on the location and urgency of all data used by the processors. Since MESI protocol used to maintain caches coherency in Xeon based multi-processor systems requires each of the CPUs to follow the processor bus of the other one, Snoop Filter allows reducing parasite traffic along processor busses significantly.
Two FSB busses and Snoop Filter are certainly a good thing for every dual-socket system, such as Skulltrail. But not all the i5400B Express features are equally advantageous for this platform. Server roots of the i5400B Express that are absolutely redundant for Skulltrail surface in the memory subsystem. They are the reason why D5400XS mainboard requires exotic for desktop systems FB-DIMM DDR2 memory modules. These modules look really nice in servers and workstations but in desktops are somewhat weird, I have to say. Their major feature is serial data transfer interface instead of the classical parallel one and it can really be beneficial if there are a lot of large capacity modules installed into the system at the same time. This is an absolutely useless feature for Skulltrail, especially since D5400XS mainboard has only four DIMM slots.
But we have no choice: potential Skulltrail owners will have to put up with all the disadvantages of using FB-DIMM such as slow speed and high power consumption and heat dissipation. According to our tests, even a four-channel memory controller of the i5400B Express chipset doesn’t help here: regular dual-channel DDR2 SDRAM works much faster, not to mention a much more up-to-date DDR3 SDRAM. Moreover, to achieve maximum performance on a Skulltrail platform you need to have four memory modules, i.e. all available memory slots need to be occupied.
However, we should give Intel engineers due credit: they did their best to make Intel D5400XS Desktop Board look as close to an enthusiast mainboard as possible, despite not the best chipset choice. For example, this mainboard features four PCI Express x16 slots. And even though i5400B Express chipset features 32 PCI Express lanes that can be split into 4 PCI Express x8 busses, the developers introduced a different and way more interesting implementation.
Available lanes are split between two PCI Express x16 busses with an Nvidia nForce 100 SLI bridge connected to each of them. This chip dynamically distributes the bandwidth of one PCI Express x16 bus between the two. Here I would also like to add that although i5400B Express supports new version of PCI Express specification, all graphics busses on D5400XS work only in PCI Express 1.1 mode, which is determined by the peculiarities of nForce 100 SLI chips.
It is also important that Intel engineers managed to avoid formal problems with SLI support thanks to Nvidia chips used on their D5400XS Desktop Board. That is why this mainboard became the first product on a third-party chipset that actually supports Nvidia SLI without any driver modifications. Of course, there are no problems with CrossFire support, too. In other words, D5400XS can work with almost any configurations with several graphics cards, which is an indisputable advantage of this product.
However, it turned out that Intel D5400XS doesn’t in fact support triple- and quad-SLI because of the notorious driver limitations. Nvidia drivers only allow SLI mode for those two graphics cards that are installed into the slots powered by the same nForce 100 SLI chip.
Another step towards computer enthusiasts was the introduction of the new cooler retention mechanism on Intel D5400XS. Luckily for hardcore users, the retention holes in the mainboard PCB are compatible with LGA775 cooling solutions and do not require server LGA771 cooling systems. It allows using Skulltrail platform with numerous efficient cooling solutions including not only the air coolers, but also liquid-cooling systems.
Intel D5400XS also has a few other features that make it look like a real overclocker platform. You can see that it has popular Power and Reset buttons as well as a POST-indicator.