Graphics systems tackle visual workload

When Dorothy visited Oz, she saw a horse of a different color. And
when PC users move up to Silicon Graphics Inc. workstations, it’s like visiting the
Emerald City. Impossible things suddenly get easy.

Silicon Graphics makes midrange and high-end workstations, servers and supercomputers,
all oriented to visual computing. If you have admired movie special effects in the last
several years, chances are the most eye-popping ones came from an SGI system.

The GCN Lab kicked the tires of an SGI Octane MXI workstation for an accompanying
review to see how and where it delivers so much graphics horsepower (see story, next
page).

The test machine, an Octane MXI, falls in the middle of Silicon Graphics’ Unix
workstation lines: the O2, the Octane and the Onyx2. The company also plans a separate,
high-performance line of Intel-based workstations for Microsoft Windows NT, reportedly for
release later this year.

Current SGI workstations have 64-bit RISC processors completely different from Intel
Corp.’s 32-bit complex-instruction-set-computing architecture. SGI’s internal
system architecture is different, too. Where a PC has a data bus, SGI puts a crossbar
switch.

You could think of the two as a shared network hub (PC bus) compared with a network
switch (crossbar switch). On the hub, all nodes share a bandwidth pool. If one node uses
lots of bandwidth, other nodes have less available. But on a switch, each node receives
the same amount of bandwidth, no matter what other nodes are doing.

The PC’s resources must battle for bandwidth to system memory. The SGI
architecture dedicates a set amount to each resource—in the test system, 2.1G per
second. The performance boost gained here is considerable.

SGI workstations specialize not only in impressive graphics but also in easy handling
of the data behind the images. An extra called a geometry texture board is necessary to do
real-world simulations, such as virtual combat training or realistic 3-D computer-aided
design.

Add a second processor to an SGI workstation, and you can develop visual information
even faster, or you can set one processor working on image display while the other
crunches numbers behind the image.

Irix, SGI’s version of Unix, has excellent scalability for adding CPUs to do
symmetric multiprocessing. For even greater flexibility, the Octane has four XIO
input/output option slots. An XIO add-on might furnish, for example, two-port Fibre
Channel connections, four-port 100Base-TX networking or enhanced graphics capabilities.

Perhaps the most remarkable thing to a PC user is how easy it is to upgrade an SGI
machine. Every single major component in the Octane can be replaced or upgraded in a
modular design more sophisticated than that of a PC.

It all comes at a price. Low-end SGI workstations cost less than $15,000, but to enjoy
all the power of this platform, expect to spend $20,000 to $40,000 for a midrange Octane
and more for an Onyx2.

The O2, the cheapest SGI system, is far from underpowered. It has almost all the
features of the other workstations plus many features that you could not find on
high-powered PCs.

The Octane has even more power, features and expandability, and the Onyx2 is really
more a graphics-oriented supercomputer than a workstation. SGI’s Intel line will
likely have power similar to that of an O2 or low-end Octane, but at a lower price.

Silicon Graphics also plans to port its Irix operating system, just released in Version
6.5, to the 64-bit Intel Corp. Merced platform, ready sometime after 2000. It plans to
continue developing Irix for both platforms but, depending on user demand, it conceivably
could stop developing for RISC computers.

These fluid plans are somewhat confusing to buyers mulling the new so-called PC
workstations vs. O2 or Octane systems. The PC workstation’s price is hard to ignore,
but there are other purchasing factors to consider beyond price vs. the processing
advantages of 64-bit Unix.

Once a dual-processor Pentium II workstation is loaded up with 384M of memory, two 12G
SCSI hard drives, $1,000 graphics card and geometry texture board, there’s not much
of an upgrade path left.

On the other hand, SGI’s standard RAM starts at 128M and goes to 2G. Its standard
features would cost extra on PCs, such as digital and analog outputs for audio and video,
two Ultra SCSI controllers, 10/100-Mbps network connectivity and bundled software.

In other words, by the time you configure a PC workstation with the same features as an
SGI, you probably have spent just as much money. And you are stuck with an architecture
not optimized to take advantage of all the parts you bought.

For a PC user who has spent years in MS-DOS or Windows, breathing the rarefied
atmosphere of the high-end graphics workstation can be addictive. It might sound frivolous
to want to play real-time video on each side of a rotating virtual cube, but the
possibility of doing so is what makes Silicon Graphics a horse of a different color.