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Quick on the draw

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computing; The unusual architecture of SGI's Visual 320 frees up enough memory to stop bottlenecks, but don't rush to buy it yet

sgi has just upgraded its nt-equipped range of Visual workstations to use the newer, faster Pentium III chips from Intel. The serial number stays the same, and the units will be shipped as 450, 500 and 550mhz versions. We had the 500mhz version of the single-processor 320 to look at, complete with the 1600 sw flat-panel lcd monitor.

For those not familiar with these machines, it is worth noting that their architecture is unlike any other desktop machine on the market - pc or Mac. Memory on most machines is divided into two pools: video memory, which is provided by the graphics card, and system memory, which is the main ram used for applications and the operating system. The 'crossbar' architecture in the sgi machine lumps all memory into one pool, which can be partitioned between graphics and system as needed. It's possible to use all available free memory (after systems and applications) as texture memory. The benefits claimed for this system by sgi are twofold: first, flexibility, for the aforementioned reasons, but also, by eliminating video-card and processor bottlenecks, the processor-memory bandwidth is a claimed 3.1gb a second, a six-fold increase over the 500mb a second found in most machines. The graphics acceleration itself is provided by sgi's own Cobalt chipset.

The machine ships with a version of nt that includes Service Pack 4.0, but it's also a version of nt that has been specially tweaked to run on the sgi architecture. The cd that comes with the machine is the only one that can be used for installation or repair, so it's a good idea to burn a few backup copies immediately. The only visible difference in running this and bog-standard nt 4.0 is in the very tasteful and irix-inspired startup screens. Other than that, you're at the mercy of Redmond's finest. To show that sgi is serious about the integration of the Visual workstations into mixed environments, the 320 ships with a slew of connectivity options to integrate it into unix and Macintosh networks. Included in the sgi Interoperability Toolkit are (among other things) Hummingbird Connectivity tools, pc Maclan and Debabelizer Pro 4.5.

The 320 shares the sweeping curves and colour schemes found in all sgi machines, with the power switch, floppy and 32 x cd-rom drives hidden behind a touch-activated front drawer. However, there's no Zip drive, or any high-format removable, recordable media. Behind this lurks a suspiciously ordinary black pc casing. The struggle to get the blue side panel off and on confirms the suspicions: the 320 is a bit of a sheep in wolf's clothing in terms of industrial design. It has none of the ingenuity and modularity of the company's own o2 systems, or of Apple's new g3 designs. The inside is, however, commendably clutter-free with access to all pci slots and ram slots. There are 12 ram slots, enabling a total of 1gb of ram, but the sgi machines use proprietary and very expensive ecc-dimms, which push the cost of usable memory configurations up quite highly.

Testing of the graphics subsystem was done using accelerated Opengl animation playbacks, since this is where nearly all of the 320's graphic muscle is concentrated. Settings were for professional graphics and animation, which allocates a nominal 56Mb to the graphics subsystem. As you would expect, this area was very impressive indeed, with the 320 managing around twice the frame rate of an Evans & Sutherland Galaxy-equipped pc, with 16mb vram, 20mb Texture ram, and easily showing a clean pair of heels to a g3-upgraded PowerMac, since there's no Opengl hardware acceleration available on the platform at the time of writing. Manipulation of heavily textured models with multiple layers and masks was where the 320 really shone, with its almost limitless texture memory meaning that bottlenecks were never a problem.

The total price of the 320/1600 sw bundle comes to a fairly impressive £4809, including 256mb ram, which compares very favourably with other machines of similar power.

However, if you can hold on for another few weeks before rushing out and buying a new machine, Intergraph's new zx1 work station holds out a great deal of promise as does the soon-to-ship sgi 540. We'll let you know how it compares with sgi's offering as soon as we get our hands on one!

'For those not familiar with these machines, it is worth noting that their architecture is unlike any other desktop machine on the market - pc or Mac.'

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