Microsoft Corp.'s Xbox is more of a minimalist PC with souped-up graphics than, say, Sony's Playstation 2 or Nintendo's Gamecube, both of which are closer to pure game platforms in design and interface. In fact, the Xbox has been architecturally tuned to deliver gaming performance with a potentially broader future thanks to its PC heritage.
Xbox is claimed to provide processing speed of 125 million polygons/second or more through an architecture that includes a 733-MHz Intel Pentium III, 250-MHz Nvidia graphics processing unit (XGPU), Nvidia media and communications processor (MCPX) and Samsung double-data-rate (DDR) SDRAM. A $30 adapter lets you play movies on the built-in 5x DVD drive. With the internal 10-Gbyte hard disk and an Ethernet interface, more-diverse capabilities may well emerge in the Xbox's future.
Design details underscore the differences between the Xbox and a standard PC. For instance, much of the modularity and expandability of the conventional PC is absent, and a single motherboard clearly runs the show. Key circuitry is implemented on this four-layer, 419-cm2 (65-inch2) motherboard, including extensive delay-matched transmission-line routing for the high-speed buses. Despite four unpopulated SDRAM sites, no memory sockets are used-likely a move to reduce cost and minimize performance-numbing parasitic loads.
Unlike a traditional PC, Xbox uses a unified memory architecture where all processors access the same 64 Mbytes of DDR memory. A 128-bit, 6.4-Gbyte/s bus connects the DDR memory bank to the XGPU, where memory-access traffic is managed. Additionally, an AMD HyperTransport bus connects the XGPU and MCPX, and a 64-bit, 1-Gbyte/s bus links the Pentium III CPU and Nvidia XGPU.
More conventional PC-like touches include a single, daisychained flat-ribbon cable to connect the hard-disk and DVD-ROM drives to the motherboard. A separate internal power supply assembly provides power to the board via a 12-wire cable assembly.
Nearly 1,300 components populate the Xbox, exclusive of the DVD assembly, hard drive and controllers-pretty fancy pieces of design by themselves. Spread across seven separate circuit-board assemblies are 29 ICs and 1,248 discretes, passives and connectors. Yet the total semiconductor die area is 5.3 cm2-less than some cell phones and PDAs.
The cost-of-goods-sold for Xbox is an estimated $323, including accessories (table). With a cost-to-produce in excess of the $299 retail price, the Xbox is clearly the profitless hook to entice purchases of high-margin software and accessories. Microsoft's challenge is to develop a lucrative software sales and licensing business to wrap around that loss-leader hardware. Let the games begin.
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DAVID CAREY IS CEO OF PORTELLIGENT (WWW.PORTELLIGENT.COM). THE AUSTIN, TEXAS, COMPANY PRODUCES TEARDOWN REPORTS ON ELECTRONICS SYSTEMS.
