SGI reinvents NT workstations

DN Staff

January 18, 1999

8 Min Read
SGI reinvents NT workstations

Mountain View, CA--Bill Gates wants one. He said so during his keynote at Fall Comdex when he shared the spotlight for a moment with Tom Furlong, senior vice president and general manager of Silicon Graphics' workstation division.

Gates was lusting after SGI's new Windows NT workstation and high-resolution digital flat-panel monitor. The machine--which Furlong demoed at the keynote--is the company's first foray into Wintel territory.

"Until now, vendors have taken standard Intel core-logic chipsets and added graphics boards to make a workstation out of what is fundamentally a PC architecture," says Furlong. Instead, SGI redefined the traditional PC architecture. Engineers created a large pool of memory available to all devices, integrated graphics onto the motherboard, and developed their own ASIC chipset instead of using Intel's.

Result: A machine that eliminates many PC bottlenecks but is still 100% compatible with Windows NT-certified off-the-shelf applications. "The SGI NT workstation offers unmatched 2D and 3D graphics performance, including 2D and 3D acceleration," says Kevin Connors, SGI product manager. "It's a breakthrough architecture."

SGI employees and Gates aren't the only ones excited. "It'll be revolutionary to the NT paradigm," says Dataquest Industry Analyst Dan Dolan. "No other vendor is modifying the PC architecture. Other companies are using snazzy graphics cards on the PCI or Intel AGP 2X graphics bus."

There's more: "This computer was built for mechanical engineers," continues Dolan. "They won't have to worry about PCI latencies and graphics cards, since the graphics are built into the silicon."

Move from Unix. Most people think of SGI as a big player in the high-end Unix market, and it is. But as the firm's market and market share declined, SGI decided to put its skills into developing a high-end NT workstation using Intel's Pentium II and Xeon microprocessors. The goal was to leverage the PC market's economy of scale while adding SGI-class performance at a competitive price.

The design team studied the standard PC architecture, which was designed for the consumer market, and decided it couldn't deliver the performance engineers demand. But their NT workstation had to be fully compatible with that architecture so it could use Intel processors and run all the engineering applications compatible with the Windows environment.

The major limitation of the PC architecture is that everything plugs into the PCI bus. This results in a lot of traffic along the bus and creates bottlenecks, especially as users add high-byte-rate devices. Graphics cards were getting faster and faster, so to ease bus congestion Intel introduced chipsets that supported the AGP 2X dedicated graphics bus. This move helped, but the PCI bus was still overloaded. The new bus also didn't address another bottleneck: having to copy data from memory to memory to process data from any of the add-in cards.

SGI's solution: Break the bottlenecks by developing a new but compatible architecture optimized for high performance--especially 2D and 3D graphics.

The Integrated Visual Computing (IVC) architecture does just that, says SGI, thanks to its Unified Memory Architecture (UMA)--a second-generation design based on SGI's O2 Unix workstation architecture. IVC embeds graphics functions into the SGI-designed Cobalt core-logic chipset. The chipset comprises three ASICs: graphics, and display and I/O engines (see sidebar).

The graphics engine connects to main memory via a 256-bit-wide, 3.2-Gbyte bus, which is six times the bandwidth of the AGP 2X graphics bus. The higher bandwidth lets users work with larger, more complex models and achieve greater realism.

The I/O systems have dedicated connections to the I/O engine, so they don't have to fight for space on the PCI bus and don't require PCI cards with their own memory chips. The PCI bus is 133 Mbytes/sec; the SGI I/O bus is 1.6 Gbytes/sec.

Why ASICs? Designing the three ASICs increased the design cycle to 18 months and delayed the workstation's introduction by at least two months.

"But we couldn't have done the design with standard parts," says Joe Chien, engineering director at SGI's consumer products division. "We needed specialized parts, and they didn't exist." The ASICs not only enabled the design, but increased integration and flexibility, lowered part count, and made the workstation more rugged, he says.

A minor problem with one of the ASICs moved the intro date from fall of 1998 to January 1999. The flaw would have affected very few users, according to Chien. But SGI didn't want to compromise quality on its first NT product, so the team found the flaw, fixed it, retested the design, and went back to the foundry to manufacture the chip.

Industry analyst Dolan says they made the right decision: "You know how first impressions are. It would be worse if SGI brought out a product and then had to do a recall. Delaying the introduction was better than making the November date."

Legacy woes. The biggest design challenge for Chien was dealing with the PC hardware and software legacy--a first for SGI.

"With NT, we don't control the operating system anymore," he says. With Unix systems, SGI would design its own hardware architecture and change the operating system to support it. For example, software engineers had to change a lot of Irix to support the O2 workstation. They could do that because SGI owns Irix.

"We went into this world where the most important thing is compatibility, compatibility, compatibility," says Chien. He and the team had to make sure all the software was binary compatible so it wouldn't need to be recompiled. They also had to be sure PC peripherals would work with the SGI architecture.

SGI's two Windows NT workstations are the Pentium II-powered 320 and the Xeon-based 540. The 320 is available with one or two Pentium IIs; the 540 is scalable from one to four Xeon processors. Main memory ranges from 128 Mbytes to 2 Gbytes. I/O interfaces include: fast Ethernet, 1394 Firewire, USB, video (two streams, uncompressed), serial, parallel, and Ultra 2 SCSI for 540. The 540 also has optional support for two streams of uncompressed digital video I/O.

The 540 has two 64-bit PCI buses that together provide six full-length 32/64-bit 33-MHz slots. The 320 has one 64-bit, 33-MHz PCI bus having two full-length 32/64-bit slots and one half-length slot.

Free software helps users interoperate with coworkers on Unix. SGI is working with some long-time Unix partners checking out the NT space to help them optimize their products for the new architecture. Other partner companies only make NT software but are working with SGI to boost performance. Partner companies include: Autodesk, SDRC, ANSYS, SolidWorks, Dassault Systemes, The MacNeal Schwendler Corp., and Unigraphics.

Flat panel goes digital. Silicon Graphics wanted a no-compromise display to match the performance of its NT workstation family. It turned to Mitsubishi, one of the leaders in flat-panel technology. Together they designed the 1600SW--a high-resolution pure digital flat panel loaded with eye-catching and -pleasing features.

Consider the following:

The 17.3-inch 1600SW offers the same viewing area as a 19-inch CRT but is one-tenth the weight.

  • The digital panel is three times brighter than CRT, and has a contrast ratio about seven times higher.

  • Most high-end flat-panel displays have a dot pitch of 0.28 to 0.31 mm, resulting in a resolution of less than 90 dpi. The 1600SW has a 0.23-mm dot pitch and 110-dpi resolution.

  • SGI's flat panel provides 24-bit true color (16.7 million simultaneous colors) with no dithering, and high levels of color saturation, brightness, and contrast.

  • Users can adjust the white balance independently from the gray scale. Colors are calibrated at the factory, and users can recalibrate them and perform color management.

All told, SGI has about 12 patents pending for 1600SW technologies.

Why digital? A huge amount of digital data comes screaming out of a computer for display. For an analog-interface flat panel, the display data is converted to analog to reduce its bandwidth, then back to digital because the panel itself is digital. When digital data is converted to analog then back to digital, two things happen: Quality is degraded and information is lost.

A panel with a digital interface doesn't go through the analog-conversion phase, so images are much more crisp and stable. A pixel is in the same place every time. Maintaining a digital signal from the graphics subsystem to the display drivers results in no signal or clock degradation.

Choice of standards. No universally agreed-upon standard exists for digital flat-panel displays. In the U.S., two competing protocols are low-voltage differential signaling (LVDS), which can support resolutions up to 2,048 3 1,536, and transition minimized differential signaling (TMDS), which PC makers favor.

Neither one offered SGI a "no-compromise" solution because of bandwidth limitations. "So we developed

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