VOLUME 13, NUMBER 5 APRIL 19, 1999 MICROPROCESSOR REPORT THE INSIDERS’ GUIDE TO MICROPROCESSOR HARDWARE Sony’s Emotionally Charged Chip Killer Floating-Point “Emotion Engine” To Power PlayStation 2000 by Keith Diefendorff rate of two million units per month, making it the most suc- cessful single product (in units) Sony has ever built. While Intel and the PC industry stumble around in Although SCE has cornered more than 60% of the search of some need for the processing power they already $6 billion game-console market, it was beginning to feel the have, Sony has been busy trying to figure out how to get more heat from Sega’s Dreamcast (see MPR 6/1/98, p. 8), which has of it—lots more. The company has apparently succeeded: at sold over a million units since its debut last November. With the recent International Solid-State Circuits Conference (see a 200-MHz Hitachi SH-4 and NEC’s PowerVR graphics chip, MPR 4/19/99, p. 20), Sony Computer Entertainment (SCE) Dreamcast delivers 3 to 10 times as many 3D polygons as and Toshiba described a multimedia processor that will be the PlayStation’s 34-MHz MIPS processor (see MPR 7/11/94, heart of the next-generation PlayStation, which—lacking an p. 9). To maintain king-of-the-mountain status, SCE had to official name—we refer to as PlayStation 2000, or PSX2. do something spectacular. And it has: the PSX2 will deliver Called the Emotion Engine (EE), the new chip upsets more than 10 times the polygon throughput of Dreamcast, the traditional notion of a game processor. Whereas game leaving it and other competitors in the virtual dust. CPUs have typically been cheap and wimpy compared with With DVD-ROM, Dolby Digital (AC-3) and Digital those in PCs, the EE is neither. At a whopping 240 mm2 in a Theater System (DTS) sound, 32M of memory, a modem, 0.25-micron process, the 10.5-million-transistor chip will cost IEEE-1394, and USB, the PSX2 system could be more than more than $100 to manufacture, according to our cost model. just a game console. Able to perform many of the functions Never mind the companion 279-mm2 rendering chip, called for which people buy sub-$600 PCs, the PSX2 has the poten- the graphics synthesizer (GS), or the I/O processor (IOP), tial to swipe a chunk of the low-end market from under the which includes a complete first-generation PlayStation CPU noses of PC vendors, x86 vendors, and Microsoft. The PSX2 for backward compatibility, as Figure 1 shows. The EE and GS die sizes are frightening; vendors of PC Emotion Engine Graphics Synthesizer processors break out in a cold sweat at the mere thought of a 300-MHz Vector Vector 16 Parallel 2 Superscalar die larger than about 180 mm . How Toshiba and SCE intend Unit 0 Unit 1 64-bit Pixel Processors CPU Core (VPU ) (VPU ) to build two chips larger than that for a consumer game con- w/128-bit SIMD 0 1 150 (150 MHz) Graphics I/F MHz sole is unclear. But the companies are intent on doing so; two 1,024-bit 1,024-bit 512 large fabs are now being readied for just this purpose. 128-bit/150-MHz Bus While the EE is not cheap, neither is it wimpy. The Video Memory (4M multiported 300-MHz part packs a floating-point punch of 6.2 GFLOPS, Memory 10-Ch IPU I/O embedded DRAM) Control DMA (MPEG I/F VESA DTV, NTSC, PAL, three times that of Intel’s top-of-the-line 500-MHz Pen- Decoder) tium III with SSE (see MPR 3/8/99, p. 1) and 15 times that of 400 MHz 37.5 MHz a Celeron-400 (which lacks SSE). With the EE pumping out I/O Processor 32-bit 48-Ch DVD-ROM 75 million polygons per second and the GS drawing polygons 16-bit 16-bit Sound Chip 34-MHz Local Bus at 2.4 billion pixels per second, the PlayStation 2000 will MIPS CPU I/O Main Memory bring Toy Story–like realism to home games, says SCE. (PlayStation Circuits PCMCIA 32M DRDRAM compatible) USB Modem IEEE-1394 PlayStation Rules Since 1994, when it was first introduced, the PlayStation has Figure 1. PlayStation 2000 employs an unprecedented level of amassed sales of 54 million units and has now reached a run parallelism to achieve workstation-class 3D performance. 2 SONY’S EMOTIONALLY CHARGED CHIP could also throw a monkey wrench into the plans of dozens objects. And the properties of Silicon Valley startups (such as VM Labs) working on of materials such as water, EMBEDDED DVD-based home-entertainment gizmos and could cut wood, metal, and gas will all deeply into the market for WebTVs and similar devices—an be accurately simulated. event we have already forecast (see MPR 6/22/98, p. 3). Floating Point Key to Totally New, But Still Backward Compatible Emotion On its own merits, the PSX2 will be compelling enough to Making the vision of emo- attract a large following. But to be safe, SCE will lure current tion synthesis a reality will customers to PSX2 by making it backward compatible with require massive floating- PlayStation. This compatibility will, it hopes, prevent the point computational horse- Osborne effect and avoid a drop in sales of PlayStation games power. To deliver these capa- Figure 2. PlayStation 2000 to those anticipating the new platform, which won’t arrive bilities, the EE provides screenshot. (Source: Namco) until 4Q99 in Japan and 3Q00 elsewhere. Lack of compatibil- several autonomous proces- ity prevented previous game-console manufacturers from car- sing units, as Figure 3 shows. rying momentum from one generation to the next. The EE chip itself includes a dual-issue superscalar SCE takes the brute-force approach to compatibility: it core with 128-bit SIMD-integer capability and a scalar will simply include an identical copy of the PlayStation CPU floating-point unit. This core is tightly coupled to a vector in the new platform. So as not to waste silicon, this CPU floating-point unit (VPU0); together the core and VPU0 serves as the PSX2’s I/O processor when running new games, run the game code and perform the high-level modeling switching to the role of central processor to run old games. computations. VPU0 can also be pressed into service for With this approach, the performance and quality of legacy 3D-geometry transformations when it is not otherwise games will be the same as on the original PlayStation. occupied. A second vector floating-point unit, VPU1, is dedicated Emotion Is the Difference to 3D geometry and lighting. This unit runs independently, Although the EE provides conventional polygon-based ren- in parallel with the CPU, under microcode control. An dering, it also supports more computationally complex autonomous image-processing unit (IPU) and a 10-channel curved surfaces, using NURBS-based (nonuniform rational DMA controller also operate in parallel with the CPU. All B-splines) models, significantly boosting image quality. But units pass graphics-display-list entries to the graphics inter- much of the EE’s compute power will go toward an even face (GIF), which prioritizes requests and passes them to the loftier goal: behavioral synthesis, or, as SCE calls it, emotion graphics synthesizer for rendering. All units connect through synthesis. This technology gives game programmers the an on-chip shared 128-bit bus to a dual-channel Direct Ram- ability to accurately model all manner of physical systems, bus DRAM (DRDRAM) memory controller. allowing realistic behavior of characters and objects. For example, the system will enable lifelike facial expressions, as MIPS at the Core Figure 2 shows. The digital wind will ruffle hair and clothes. The heart of the Emotion Engine is a superscalar RISC core Gravity, mass, and friction will influence the motion of with two 64-bit integer units and a single-precision scalar FPU. Although SCE and Toshiba in their ISSCC paper said the CPU Core VPU0 VPU1 EE would operate at 250 MHz, SCE says the product will actu- VU1 EFU 1.2 GB/s FPU IU IU VU0 ally ship at 300 MHz. At that speed, the core achieves a Dhry- 0 1 4 FMACs, 1 FMAC, 64 4 FMACs,1 FDIV 1 FDIV 1 FDIV GIF stone 2.1 rating of 436 MIPS using the GNU C compiler. 16K 8K 16K 128 4K 4K 16K 16K Based primarily on the MIPS III (R4000) architecture, I$ D$ SP VU- micro- micro- VU- the core also includes many of the MIPS IV (R5000/R10000) RAM MEM0 MEM0 MEM1 MEM1 instructions. But instead of the MIPS-standard MDMX 2.4 GB/s 64-bit SIMD-integer instructions, SCE defined a completely 128 IPU new set of 128-bit SIMD-integer instructions. The 107 new Interrupt 10- Memory FIFO CSC VQ I/O instructions are implemented by doubling the width of the Control, Channel Controller Inter- general-purpose registers to 128 bits and ganging together the Timer, DMA (dual VLD Zig- IDCT IQ face SIO Unit RAC) zag two 64-bit integer units to process 128-bit-wide SIMD oper- Macroblock Decoder ands. Together, the two units can perform four 32-bit, eight 16 16 32 16-bit, or sixteen 8-bit integer arithmetic operations each 3.2 GB/s 150 MB/s cycle. SIMD instructions include add, subtract, multiply, Figure 3. divide, min/max, shift, logical, leading-zero count, 128-bit The PSX2’s Emotion Engine provides ten floating-point → multiplier-accumulators, four floating-point dividers, and an load or store, and 256-bit 128-bit funnel shift.