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Model2 cpu.jpg

Sega Model 2 was a arcade system board developed by Sega AM2 in 1993 as a direct evolution of the earlier Model 1. The board was state-of-the-art for its time, costing $2,000,000 to develop. The system would power arcade hits of the mid-1990s such as Daytona USA, Virtua Fighter 2 and The House Of The Dead.

History

Designed by Yu Suzuki of Sega AM2 and co-developed by Sega and GE Aerospace (now a part of Lockheed Martin), the Model 2 was an advancement of the earlier Model 1, which ran the arcade hit, Virtua Fighter. It featured texture-mapping, which allowed for polygons to be painted with bitmap images, in addition to innovative texture filtering, texture anti-aliasing and trilinear filtering features. This made it the most powerful system of its time, equivalent to a late-1990s PC graphics accelerator card.

It was stated by Suzuki that the texture-mapping chip originated "from military equipment from Lockheed Martin, which was formerly General Electric Aerial & Space's textural mapping technology. It cost $2 million dollars to use the chip. It was part of flight-simulation equipment that cost $32 million. I asked how much it would cost to buy just the chip and they came back with $2 million. And I had to take that chip and convert it for video game use, and make the technology available for the consumer at 5,000 yen ($50)" ($84 in 2014) per machine. He said "it was tough but we were able to make it for 5,000 yen. Nobody at Sega believed me when I said I wanted to purchase this technology for our games." Suzuki had also stated that, in "the end," it "was a hit and the industry gained mass-produced texture-mapping as a result." For Virtua Fighter 2, he also utilized motion capture technology, introducing it to the video game industry.

There were also issues with working on the new CPU, the Intel i960-KB, which was just released in 1993. Suzuki stated that at the time, there wasn't a debugger for the i960-KB, which resulted in the hardware being heavily bugged, and that even if a debugger existed, it'd be bugged, too. He had to debug the debugger. Of course, with new hardware, there wasn't a library or a system for it, so he had to create all of that.

According to a late 1998 interview with former GE Aerospace (now part of Lockheed Martin) employee Jon Lenyo, the development for the Model 2 started as far back as November 1990, when he and other GE Aerospace employees demonstrated their trilinear texture filtering and shading technology to Sega. As Sega was already working on the Model 1 at the time, they eventually incorporated the technology into the Model 2.

Despite the high price tag of $15,000 USD (equivalent to $24,489 USD in 2014), the Model 2 hardware was massively successful in the arcade industry, and had become an all-time best-seller.

Technical Specifications

  • Board Composition: CPU Board, Video Board, Communication Board, ROM Board, Sound Board, Feedback Driver Board
    • Revisions: CPU Board 837-10071 (50 MHz), Video Board 837-10072 (50 MHz), Communication Board 837-10537, ROM Board 834-10798, Sound Board 837-8679 (20 MHz), Drive Board 838-10646
  • Main CPU: Intel i960-KB @ 25 MHz
    • Fixed-point arithmetic: 32-bit RISC instructions @ 25 MIPS
    • Floating-point unit: 32/64/80‑bit operations @ 13.6 MFLOPS
    • Bus Width: 32-bit
  • Additional CPU(s): 2x Zilog Z80 (8/16-bit instructions @ 1.74 MIPS)
    • Communication Board: 8 MHz (1.16 MIPS)
    • Feedback Driver: 4 MHz (0.58 MIPS)


  • Sound CPU: Motorola 68000 @ 10 MHz (16/32-bit instructions @ 1.75 MIPS)
  • Sound chip(s): 2x Sega 3315-5560 Custom MultiPCM
    • PCM Channels: 56
    • PCM sample ROM: Up to 16MB (8MB per PCM chip)
    • PCM Quality: 16‑bit depth, 44.1 kHz sampling rate (CD quality)
  • Sound Timer: Yamaha YM3834 @ 8 MHz (Model 2 only)


  • Memory: Up to 62 MB (10,881 KB main, 35,460 KB video, 16,960 KB audio, 18 KB other)
  • System RAM: 9776 KB (9.546875 MB)
    • Main RAM: 1152 KB (1.125 MB)
    • VRAM: 5984 KB (1 MB framebuffer VRAM, 64 KB coprocessor buffer SRAM/SDRAM, 4 MB texture SRAM/SDRAM, 128 KB luma, 32 KB geometry, 576 KB tiles, 64 KB colors)
    • Audio RAM: 576 KB
    • Other RAM: 2064 KB (16 KB backup SRAM/NVRAM, 2 MB extra RAM)
  • Internal processor memory: 36.75 KB
    • CPU cache: 768 bytes [14]
    • TGP internal RAM: 36 KB (6 KB per TGP)
  • Game ROM: Up to 54.25 MB
    • Main ROM: 9.5 MB (EPROM, MROM)
    • Video ROM: 28.75 MB (MROM)
    • Audio ROM: 16 MB (MROM)


  • System RAM bandwidth: 974 MB/sec
    • Main RAM bandwidth: 112 MB/sec
      • i960: 100 MB/sec (32‑bit, 25 MHz)
      • Z80: 12 MB/sec (2× 8‑bit, 8/4 MHz)
    • VRAM bandwidth: 883.34066 MB/sec
      • TGP: 384 MB/sec (6× 32‑bit, 16 MHz)
      • Video Board: 499.34066 MB/sec
        • 315‑5292 & 315‑5644: 30.769232 MB/sec (2× 16‑bit, 7.692308 MHz)
        • 315‑5645: 28.571428 MB/sec (16‑bit, 14.285714 MHz)
        • 315‑5646 & 315‑5647: 400 MB/sec (2× 32‑bit, 50 MHz)
        • 315‑5712: 40 MB/sec (8‑bit, 40 MHz)
      • Audio RAM bandwidth: 20 MB/sec (16‑bit, 10 MHz)
  • Internal processor bandwidth: 484 MB/sec
    • CPU cache: 100 MB/sec (32‑bit, 25 MHz)
    • TGP internal RAM: 384 MB/sec (6× 32‑bit, 16 MHz)
  • Game ROM bandwidth: 933–1000 MB/sec (5× 32‑bit)
    • EPROM: 133–200 MB/sec (32‑bit, 33–50 MHz, 20–30 ns)
    • MROM: 800 MB/sec (4× 32‑bit, 50 MHz)

External Links

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