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Next-generation UltraSPARC-II coming soon

Hot on the heels of the debut of Sun's UltraSPARC-I-based computers will be even faster systems

By Cynthia Kurkowski

November  1995
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As Sun Microsystems put the finishing touches on its first UltraSPARC computers, the company offered glimpses of its next generation RISC microprocessor, the UltraSPARC-II, at the Microprocessor Forum in October. At half the size of its predecessor, the 64-bit UltraSPARC-II delivers 50 percent more processing performance, yet consumes 15 percent less power running at 250 MHz.

Sun's SPARC Technology Business group disclosed design specifications for what it is calling the industry's highest data bandwidth processor, including a unique embedded multimedia "Visual Instruction Set" (VIS). UltraSPARC-II is expected to be available for production in the second quarter of 1996. (Based on Sun's first-silicon-to-first-workstations record with the UltraSPARC-I, this implies we'll see UltraSPARC-II machines in late 1996.)

[UltraSPARC chip
GIF, 72K]Remember when the acronym MIPS, which stands for millions of instructions per second, was in vogue? Sun's trying to coin a new, updated phrase -- "GOPS." Slower UltraSPARC-IIs will debut at three giga-operations per second, jumping to 4.8 GOPS when humming along at 250 to 300 MHz. At that rate, UltraSPARC-II will deliver an estimated 350 to 420 SPEC92int and 550 to 660 SPEC92fp when equipped with a 2-megabyte cache.

"UltraSPARC-II is a big step for Sun," said Linley Gwennap, editor-in-chief of the Microprocessor Report. "Sun has lagged in performance for the last two years. UltraSPARC-II makes them a competitor once more." For now, the UltraSPARC-II announcement puts Sun in the high-performance workstation game, ahead of HP and SGI. Only Digital, which seems to be in a different playing field, remains in front with the recently announced 333-MHz model and a 400-MHz model expected late next year, Gwennap said.

UltraSPARC-II resolves the performance lags associated with memory processes, reported Anant Agrawal, Sun's SPARC Technology Business vice president of engineering. UltraSPARC-II's designers consider its ability to access extra cache when processing large applications a breakthrough. The UltraSPARC-II supports a sustained throughput of one load per cycle from the secondary cache.

"The single largest factor in benchmarks is memory latency," Agrawal said. "We've added prefetch data instructions before it's needed to reduce latency delays. UltraSPARC-II can support up to three outstanding requests and up to two write-backs in flight." The software prefetch supports both reads and writes, and is automatically inserted by the compiler.

Circuit design changes and the UltraSPARC's migration from the 0.50-micron CMOS (complementary metal-oxide semiconductor) to the 0.35-micron CMOS size has also advanced UltraSPARC-II's processing power. Highest performance gains will be realized in scientific and large 32-bit applications such as databases.

UltraSPARC-II's four-way, superscalar pipeline is derived from the UltraSPARC-I pipeline with the same look and feel and approximately the same number of transistors (5.4 million). The packet-switched system interconnect enables decoupled, pipelined accesses to main memory, thereby increasing memory bandwidth. The pipeline can simultaneously process four instructions per cycle even with conditional branches and cache misses. For instance, the first instruction can have four 16-bit addition processes, the second can have four 16-bit multiplication processes, and the third and fourth instructions can consist of either a load, store, or integer.


How is UltraSPARC-II different from UltraSPARC-I

The microprocessor also features an improved memory subsystem with up to 1-gigabyte-per-second sustained data transfer rate to main memory and provides second-level cache support up to 16 megabytes. The main memory system support of 2:1, 3:1, and 4:1 system clocking gives customers a flexible, programmable upgrade path to higher processing speeds without system modification.

However, Gwennap says Sun customers will probably not be able to take full advantage of the UltraSPARC-II performance until next year when the cost of chips are expected to be cut in half. "This price drop will help move Sun into a better position to fill out the mid-range and high-end systems with UltraSPARC performance," Gwennap said.

New media processing with VIS
In addition to offering 3 GOPS performance, Sun includes multimedia- specific features in UltraSPARC-II, which the company is making available with the new Visual Instruction Set API.

Integrated new media support facilitates desktop videoconferencing, real-time MPEG-2 decoding, video effects, texture-mapping, and triangle rendering. With the use of VIS, the UltraSPARC-II is said to be especially effective in 3D visualization applications like medical imaging. The VIS array instruction reduces memory latency by eliminating the need to go to main memory. In essence, VIS claims to have brought back "spatial locality" to the 3D world.

"This is the first time a general-purpose processor can decode MPEG-2 in real-time," Marc Tremblay, computer architect for Sun's SPARC Technology Business, announced to the Microprocessor Forum crowd as he ran a clear, smooth 30 frame-per-second, action-packed video to demonstrate the power of VIS.

Today, Sun is the only company offering an available on-chip multimedia extensions. To date, only Philips Semiconductor has disclosed plans for manufacturing a full-fledged embedded multimedia RISC extension. Other microprocessor designers currently are sketching out dedicated multimedia co-processor solutions. According to Tremblay, these dedicated co-processor solutions are more difficult to program for application support since the co-processors are not part of the general-purpose processors. Dedicating a chip to multimedia is very expensive, and even more costly when the standards change and the chip must be replaced, he explained.

"VIS is like any other RISC instruction, therefore it's easier to write software for it," Tremblay said. According to H&P EuroSoft, VIS allowed the European software developer to have its beta software up and running "within a few short weeks." Other companies, including Adobe Systems and InfoGraphix Technologies, have reported up to quadruple acceleration rate increases of their applications using VIS.

VIS as an industry standard?
Tremblay noted that Sun is committed to offering VIS on Sun's entire product line. The UltraSPARC-I served as the first vehicle. Customers can expect to see VIS added to microSPARC-III, microSPARC-IV and microSPARC-IIIE systems in addition to the upcoming UltraSPARC-II. Meanwhile, the VIS team is hard at work developing a software layer and graphics library to sit on top of VIS. Tremblay said the libraries will be defined by customers.

Sun plans to market its VIS technology to systems vendors as a multimedia accelerator standard. The company introduced at Microprocessor Forum the OpenVIS program aimed at developing new media hardware and software microprocessor interfaces based on the New-Media Visual Instruction Set. Sun is joined by Adobe Systems, AEG Electrocom, H&P EuroSoft, InfoGraphix Technologies, and its SPARC Business Technology in its efforts to drive VIS as an industry standard across RISC, CISC, and other special-purpose microprocessors. To help drum up support for VIS, Sun is licensing VIS and its supporting circuitry.

"Multimedia extensions is an idea whose time has come," Gwennap said. "I do expect to see microprocessors introduced next year with similar multimedia extensions." He says while Sun has the advantage of being the first to deliver a full-fledged multimedia extensions, the PC microprocessor manufacturers are hot on their heels. Intel, NexGen, and Cyrix are expected to introduce multimedia microprocessors next year.

Tremblay would agree with Gwennap that the VIS concept is catching on. He says IBM and DEC are leaning towards an embedded multimedia extension solution like VIS. He said he believes others will follow when they realize the benefits and cost savings involved with embedded new-media processing.

"When you start adding every add-on and plug-in, it comes down to 'Why not?' The instruction set represents only a 3 percent increase in die size," Tremblay said. "From one generation to another, having the multimedia on the processor gives you benefits directly and automatically."

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