Intel Skulltrail: 2 CPUs, 8 cores, 4 GPUs, 1400 watts

Many times announced, now available to the press at least, and probably to be on sale to affluent technology freaks some time after CeBIT, the Skulltrail system, with two (overclocked) quad-core processors and up to four graphics cards, is Intel's bid for leadership in the high-end-segment. The practical usefulness of this overkill computer, which will cost at least 5000 euros, seems to be beside the point – the motto is apparently "no half-measures, let's go for it and hang the cost".

Clearly, Skulltrail was not originally Intel's idea: AMD presented a "platform" for two overclockable (dual-core) processors and up to four PCIe graphics cards, the Quad FX some fourteen months ago - though initially only for the USA. The only Quad FX board up to now, the Asus L1N64-SLI WS with an Nvidia nForce 680a chipset, was on show, more or less by chance, at CeBIT 2007. Even on its introduction, Quad FX was basically obsolete already, because Intel had presented the first quad-core processor in November 2006.

AMD had however promised that proud possessors of a Quad FX platform would be able to exchange their two dual-core Athlons later ("seamlessly") for quad-core Phenoms. This still has not been possible because of the tremendous delays with the K10 product series. The Nvidia chipset with the Quad FX is now also something of a pain for AMD; a successor to Quad FX with an AMD 700 chipset and a PCI Express 2.0 connection for four Radeon graphics cards (Crossfire X) ought really to be in the race by now.

Intel's Skulltrail is really aimed at this (so far) virtual product. As was once done with the Pentium 4 Extreme Edition, the hurried counter to the Athlon 64-FX series (as also with the Quad FX), relabelled server and workstation processors are being used. The two 45-nm Xeons, rebaptised Core 2 Extreme QX9775, each with four cores, 2×6 megabytes of L2 cache and a nominal clock frequency of 3.2 GHz, sit on the only Skulltrail motherboard so far in existence, Intel's D5400XS, in two LGA771 sockets. The chipset is the 5400 (Seaburg), which is also found in the Apple Mac Pro. It connects two FSB1600 processors with four memory channels for fully buffered (FB) DIMMs with a 400-MHz clock frequency DDR2-800/PC2-6400F) as well as two PCIe 2.0 x16 ports.

Those (two) ports are not directly usable with two graphics cards, because Nvidia blocks the SLI function on foreign chipsets; only (AMD) Crossfire would then work or one could use multiple graphics cards (such as in the Mac Pro) for multi-monitor-systems. But Intel was determined to have SLI, so it soldered two nForce 100 Nvidia chips to the board, each of them dividing the two PCIe 2.0 x16 ports into two PCIe 1.1 x16 ports. This makes SLI work, but unfortunately only two-way rather than, for example, three-way SLI as in the nForce 780i boards for Core 2 duos or quads, now on delivery. Even four-way SLI could possibly work one day but, for one thing, existing Nvidia drivers can't handle that and, for another, the Skulltrail board can "only" accommodate three graphics cards with double-width coolers.

If three GeForce 8800 Ultra cards are used, it isn't just the system price that goes sky-high (Intel isn't telling yet, but there are rumours of approximately 1500 euros per CPU, plus 400 euros for the board): power consumption also hits the roof. Even without overclocking, each processor requires 150 watts peak and, in the extreme case, each graphics card needs 230 watts. Intel consequently recommends installing a power supply unit with a nominal power of 1200 to 1400 watts. A Skulltrail test system in the c't laboratory, however, with two GeForce 8800 GTX cards, four FB DIMMs and a hard disk, only took 653 watts of mains power under full load.

Judging by its performance, Skulltrail is so far only conditionally convincing. The eight 3.2-GHz cores in conjunction with four-channel memory do score more than 20,000 Cinebench points, as (apparently) Intel had announced in a peculiar YouTube video shortly before the last IDF.

But, for lack of 3-way SLI, Skulltrail is well beaten at 3D graphics acceleration by nForce 780i boards with just one quad-core processor, the Core 2 Extreme QX9770, which is also not on delivery yet. With both systems, however, the DirectX-10 resource-gobbler Crysis, for example, can be played smoothly on a 30-inch display at full resolution.

(ehe)