Armari Magnetar Xi-SLI review

Nvidia’s new SLI (Scalable Link Interface) isn’t just for gaming. The workstation-oriented Quadro FX 1400, 3400 and 4400 cards also support the revamped dual-graphics mode. With real-time 3D rendering power every bit as important for 3D animators and CAD specialists as for gamers, SLI has lots to offer graphics professionals. Fast 3D graphics are even becoming important for video editing, with apps such as Pinnacle Liquid Edition 6 making extensive use of GPU acceleration for effects.

Although nVidia hasn’t officially announced Quadro SLI yet, we got a sneak peak of what it has to offer in a prototype from Armari. The Magnetar Xi-SLI is similar to the Magnetar Xi. Like the latter, the Xi-SLI is based around Supermicro’s X6DAE-G2 motherboard and has two 3.6GHz Xeon 800s and 2GB of registered ECC DDR2 memory.

The chassis is still black and it’s still from Supermicro, but the 743T-645W is otherwise quite a change. It can double as a 4U rackmount as well as an extremely long pedestal tower. It’s also by far the quietest Nocona Xeon-based system we’ve tested. Judicious use of passive heatsinks and quiet, temperature-controlled fans means the Magnetar is unobtrusive even when running at 100 per cent load on both CPUs.

Elsewhere, the original Magnetar’s twin 250GB Hitachi Deskstar 7K250 SATA hard disks have been replaced by a duo of Western Digital 10,000rpm 74GB Raptors, which offer less storage but are considerably quicker. The DVD writer has also been upgraded to the latest Sony DRU-710A, which writes to dual-layer DVD+R at 2.4x and single-layer DVD+R at 16x. An Iomega REV is provided for backup, plus Armari’s habitual Mitsumi 7-in-1 floppy and media reader. You’ll also find a Sound Blaster Audigy 2 ZS sound card.

But SLI is obviously the headline act. The Magnetar Xi-SLI uses two PNY Quadro FX 3400 PRO-3D cards with 256MB of graphics memory apiece. The 3400 is based on the NV45GL GPU, as is the PCI Express version of NV40, the chip behind the GeForce 6800 range. So, the 3400 is basically the equivalent of a 6800 GT, but with professional 3D app accreditation. The same small PCB connector is used to link the two cards, and the drivers work in exactly the same way as with the consumer version. Within the nVidia drivers, an extra driver tab is visible for multi-GPU, with options to turn it on and off, plus display how the load balancing is being performed.

We eschewed game testing in favour of the industry-standard professional 3D graphics benchmark, SPECviewperf. We ran both the latest 8.01 version, and the recent 7.1.1 iteration. We also tried the most recent 70.50 drivers as well as the more mature 70.41 release. The benchmarks were run with multi-GPU off and on, to show the performance benefits of SLI.

Running the 70.41 drivers, SLI mode gave some impressive performance boosts. With SPECviewperf 7.1.1, there was a 14 per cent increase in the 3dsmax-02 score, 34 per cent in Proe-02, and 51 per cent in Ugs-03. The latter two refer to Pro/ENGINEER and Unigraphics, and show that SLI has potentially large benefits for CAD/CAM, although the increase for 3D animators using 3dsmax isn’t quite so pronounced. The results with SPECviewperf 8.01 were similarly impressive, except for a decrease in the Maya-01 score. The overall scores were very respectable compared to other systems, too, as can be seen on SPEC’s website at www.spec .org/gpc/opc.data/vp8/summary.html

However, we did encounter noticeable smearing artefacts with the 70.41 drivers. These were corrected with the 70.50 update, but at the cost of most of the performance benefit from SLI. Still, these are beta drivers so we’ll have to wait for the official launch for drivers offering both performance and quality. It’s likely that there’s plenty of optimisation left to be done. Unlike 3dfx SLI, which used the two 3D accelerators to render alternate lines of the image, nVidia SLI works in two modes – alternate-frame rendering and split-frame rendering. Which mode is best for specific apps needs to be pre-programmed into the drivers. Unlike the nVidia nForce4 SLI implementation, which switches the PCI Express slots to a pair of 8x channels, the Supermicro’s E7525 keeps one slot at 16x and the other a more lowly 4x. So performance is dictated very much by nVidia’s load-balancing technology, which also needs to be optimised.