TOKYO — Sega Enterprises Ltd. turned conventional thinking about gaming systems on its head with Dreamcast, its next-generation system based on Microsoft's Windows CE operating system. By opting for an open, expandable architecture, Sega has upended the proprietary platforms that currently hold sway.

The announcement of Dreamcast in Tokyo this week ended months of silence by Sega, whose earlier system was soundly beaten in the market by Sony Corp.'s PlayStation. Dreamcast will be introduced to the Japan market in November.

Speaking via a video hookup, Microsoft chairman Bill Gates said Dreamcast establishes a new standard for the home entertainment platform.

Four major partners — Hitachi Ltd., Microsoft Corp., NEC Corp. and Yamaha Corp. — each made a significant contribution to the gaming system, and hope their respective technologies gain broader acceptance in the market, spurred on by their use in Dreamcast. "Dreamcast's success will also be their own architecture's success," said Hideki Sato, managing director in charge of Sega's hardware R&D division.

Dreamcast features: Microsoft's Windows CE environment; a customized SH4 processor provided by Hitachi; the PowerVR2 3-D graphics engine from NEC; and the XG sound engine from Yamaha. The system uses two 64-Mbit synchronous DRAMs for main memory, a 12x CD-ROM drive as a game console and an internal 33.6-kbit/second modem in its 190 x 195 x 78-mm body, which weighs 2 kilograms.

The system's Windows CE was customized to deliver faster performance, and incorporates DirectX technology as well. "[We] removed unnecessary functions and enhanced necessary functions, such as interactivity and real-time processing," said Sega's Sato. "A large part of the codes are changed, but at the API level, it is completely compatible with other Windows CE."

Hitachi's SH4 has a 128-bit graphics engine and features 360-Mips or 1.4-Gflops performance. "Both SH4 and Dreamcast provide an open development environment," said Tsugio Makimoto, senior executive managing director for Hitachi's semiconductor operations.

Just as Hitachi's SH architecture was ignited in the market when the SH2 was adopted for the Sega Saturn system, Makimoto said he expects the SH4's adoption for Dreamcast will provide a further boost for the archtecture.

Hitachi is already producing in volume production on the SH4.

NEC timed the announcement of PowerVR2, its second-generation graphics device, to coincide with Sega's introduction. NEC hopes that the chip's adoption for Dreamcast will improve its chances to be designed into another coveted high-volume market: personal computers. A game title written for Dreamcast will also run on a personal computer "or other platform," said Charles Bellfield, manager of the multimedia strategic business unit of NEC Electronics Inc. (Santa Clara, Calif.).

NEC beefed up the performance of PowerVR2 — its polygon throughput is about seven times better than the company's first-generation 3-D processor — and can now process over 3 million polygons per second. It sports a pixel-fill rate of 200 million pixels/second. "The polygon processing power is about twice higher than that of current arcade games," Bellfield said.

Yamaha's XG engine is a 32-bit embedded RISC processor that delivers 64 channel adaptive differential pulse code modulation (ADPCM) sound. Yamaha is proposing the XG format as the next-generation sound source format. It maintains backward compatibility with general MIDI, the widely implemented standard first defined in 1991.

MIDI has not kept pace with recent advances in sound technology, Yamaha said. For example, it is limited to 128 controllable timbers, and its sound-effect processing is also limited, the company said. XG was proposed to eliminate these limitations, while retaining its backward compatibility with the general MIDI format.

While Yamaha customized the XG sound processor for Sega, the supplier is now offering XG chips in volume for the merchant market.

These hardware features give Dreamcast strong graphics and sound-processing power. Image-processing abilities include bump mapping, fog, alpha blending, mip mapping, anti aliasing, environment mapping and specular effects, both interactively and in real-time, with VGA resolution and in 16.8 million full colors.

"Three-million polygons/second is about 10 times higher compared with conventional processing power," Sato said. "But total quality is 100 times better, taking consideration of various effects which Dreamcast can do."

Another gimmick exists in Dreamcast's controller. Sega intends to offer a small PDA-like accessory named Visual Memory. The unit will snap into the controller and work as an expansion memory and personal viewer. It will display data unseen by other players in games that pit multiple players against one another. The PDA itself will work as a portable game machine.

The Visual Memory accessory will actually be offered in Japan this summer, in advance of the Dreamcast game console itself. "The Visual Memory has a certain gimmick in it," Sato said.

Sega suggested that the PDA accessory may be able to connect to other PDAs, or to a portable telephone, to arcade game machines and other systems to offer still-undisclosed services.

"We thought that backup memory was mandatory," Sato said. "At the same time, if it works as a communications tool for a player in various way — for example, to show off to friends what he or she has achieved, and to exchange data with them — an LCD is essential." To run on two button batteries, the unit employs a single-chip 8-bit microcontroller, which consumes very little power. Further details about the system's memory and the supplier of the controller chip were not disclosed.

The accessory and the game system will not be introduced to the U.S. market until autumn 1999, or about a year later their introduction in Japan. At present, Sega has no plans to exhibit Dreamcast at the E3 show in Atlanta next week, but may show it to limited parties off of the show floor.