Sega Model 2

From Sega Retro

Model2 cpu.jpg
Fast facts on Sega Model 2
Manufacturer: Sega
Variants: Model 2A-CRX, Model 2B-CRX, Model 2C-CRX
Add-ons: DSB1/DSB2 (Model 2C-CRX)
Release Date RRP Code
1993-08 ¥2,200,000 [1]Media:MeanMachinesSega22UK.pdf  ?
1994-03 $15,000 [2]  ?
1994-03 £16,000 [3]Media:MeanMachinesSega22UK.pdf  ?
1994  ?

The Sega Model 2 is an arcade system board originally debuted by Sega in 1993 as a successor to the Sega Model 1 board. It is an extension of the Model 1 hardware, most notably introducing the concept of texture-mapped polygons, allowing for more realistic 3D graphics for its time. The Model 2 board was an important milestone for the arcade industry, and helped launch several key arcade franchises of the 1990s, including Daytona USA, Virtua Cop, Sega Rally Championship, Dead or Alive, Virtua Striker, Cyber Troopers Virtual-On and The House of the Dead.

The Model 2 was engineered with help from GE Aerospace (acquired by Martin Marietta in 1993, now part of Lockheed Martin), who designed the texture-mapping chip incorporated by the Model 2, which combined it with Sega's in-house polygon geometry engine.[4]Media:NextGeneration US 11.pdf The Model 2's development was led by famed Sega AM2 game designer Yu Suzuki. The arcade board debuted along with Daytona USA, a game which was finished and copyrighted in 1993, and debuted at the JAMMA arcade show in August 1993. [5]Media:EGM US 051.pdf

There are four versions of the system: the original Model 2, and the Model 2A-CRX, Model 2B-CRX and Model 2C-CRX variants. Model 2 and 2A-CRX used a custom DSP with internal code for the geometrizer, while 2B-CRX and 2C-CRX used well documented DSPs and uploaded the geometrizer code at startup to the DSP. The Model 2 was succeeded in 1996 by the Sega Model 3, which in turn was succeeded by the Sega NAOMI, Sega Hikaru and Sega NAOMI 2.


It was a further advancement of the earlier Model 1 system. The most noticeable improvement was texture mapping, which enabled polygons to be painted with bitmap images, as opposed to the limited monotone flat shading that Model 1 supported. The Model 2 also introduced the use of texture filtering and texture anti-aliasing,[6] as well as trilinear filtering.[7] It was the most powerful game system in its time, equivalent to the power of a PC graphics card in 1998, five years after the Model 2's release. [8]

Designed by Sega AM2's Yu Suzuki, he stated that the Model 2's 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."[9] Suzuki 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 game industry. [10]

There were also issues working on the new CPU,[11] the Intel i960-KB, which had just released in 1993.[12] Suzuki stated that when working "on a brand new CPU, the debugger doesn't exist yet. The latest hardware doesn't work because it's full of bugs. And even if a debugger exists, the debugger itself is full of bugs. So, I had to debug the debugger. And of course with new hardware there's no library or system, so I had to create all of that, as well. It was a brutal cycle." [13]

In a late 1998 interview, Read3D's Jon Lenyo, a former employee of GE Aerospace (later Lockheed Martin), stated that Sega's development for the Model 2 can be traced back as early as November 1990, when he and other GE Aerospace employees visited Sega and demonstrated the trilinear texture filtering and shading capabilities of their technology. As Sega was already working on the Sega Model 1 internally, they eventually incorporated GE Aerospace's technology into the Model 2. [14]

Despite its high price tag of around $15,000 [15] (equivalent to $24489 in 2014), the Model 2 platform was very successful. It featured some of the highest grossing arcade games of all time: Daytona USA, Virtua Fighter 2, Cyber Troopers Virtual-On, The House of the Dead, and Dead or Alive, to name a few. Sega sold 65,000 units of the Model 2 annually,[16] and eventually sold over 130,000 units by 1996, amounting to over $1.95 billion revenue from hardware cabinet sales (130,000 units [17][18] at $15,000 each),[19][20] equivalent to over $3.18 billion in 2014, making it one of the best-selling arcade systems of all time.

According to Yu Suzuki, the Sega Model 2B-CRX arcade system board developed for Fighting Vipers "has a slightly faster processing speed" and "a higher response to displaying more polygons".[21]Media:SSM_UK_02.pdf

Technical Specifications

Model 2 Specifications





  • 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 [51][52]
    • 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) [57][58]

Model 2A-CRX Specifications

Model 2A-CRX, released in 1994, featured upgraded sound capabilities and increased ROM capacity:

  • Sound CPU: Motorola 68000 @ 12 MHz (16/32-bit instructions @ 2.1 MIPS)
  • Sound chip: Yamaha SCSP
    • PCM channels: 56
    • PCM sample ROM: Up to 16 MB
    • PCM quality: 16-bit depth, 44.1 kHz sampling rate (CD quality)
    • SCSP features: 128-step DSP, 32 PCM/FM/MIDI/LFO channels
  • Memory: Up to 142 MB (35,969 KB main, 90,244 KB video, 16,960 KB audio, 2064 KB other)
    • System RAM: 9776 KB (9.546875 MB)
      • Main RAM: 1152 KB (1.125 MB)
      • VRAM: 5984 KB (5.84375 MB)
      • Audio RAM: 576 KB
      • Other RAM: 2064 KB (2.015625 MB)
    • Internal processor memory: 36.75 KB
      • CPU cache: 768 bytes
      • TGP internal RAM: 36 KB
    • Game ROM: Up to 132.25 MB (34 MB main, 82.25 MB video,[61] 16 MB audio)

Model 2B-CRX Specifications

Model 2A-CRX, released in 1995, featured upgraded geometry engine DSP coprocessors and increased VRAM:

  • GPU: [62]
    • Geometry Engine DSP coprocessors: 2× ADSP-21062 SHARC [63]Media:ADSP-2106 datasheet.pdf
      • Coprocessor abilities: Floating decimal point operation function, axis rotation operation function, 3D matrix operation function, SOC, ALU, T&L
      • Floating-point units: 32/40-bit operations @ 240 MFLOPS (120 MFLOPS each)
      • Fixed-point arithmetic: 32-bit instructions @ 80 MIPS (40 MIPS each)
      • Data bus width: 96-bit (48-bit each)
      • DMA controllers: 20 DMA channels (10 channels each), 480 MB/sec transfer rate (240 MB/sec each)
    • Sega Z-sort & clipping chipset
    • Lockheed Martin rasterization & texture mapping renderer units
    • Sega System 24 tilemap engine
  • Rendering fillrate: 120 million pixels/sec (2 million pixels per frame)
  • Memory: Up to 150.21 MB (35.125 MB main, 99,332 KB video, 16,960 KB audio, 18 KB other)
    • System RAM: 18,388 KB (17.957031 MB) [64]
      • Main RAM: 1152 KB (1.125 MB)
      • VRAM: 14,596 KB (1.5 MB framebuffer VRAM, 8228 KB coprocessor buffer SRAM/SDRAM, 4 MB texture SRAM/SDRAM, 64 KB luma, 32 KB geometry, 576 KB tiles, 64 KB colors)
      • Audio RAM: 576 KB
      • Other RAM: 2064 KB (2.015625 MB)
    • Internal processor memory: 512.75 KB
    • Game ROM: Up to 132.25 MB (34 MB main, 82.25 MB video, 16 MB audio)

Model 2C-CRX Specifications

Model 2A-CRX, released in 1996, featured an upgraded GPU chipset and optional MPEG sound boards:

  • GPU:
    • GPU coprocessors: 2× Fujitsu TGPx4 MB86235 [66][67]Media:3DGraphicsProcessorChipSet.pdf
      • Coprocessor abilities: Geometry Engine DSP, Z-sorters, clipping, hardware renderers, floating decimal point operation function, axis rotation operation function, 3D matrix operation function, ALU, DMA controllers, T&L
      • Floating-point units: 32/40-bit operations @ 160 MFLOPS (80 MFLOPS each)
      • Fixed-point arithmetic: 32/64-bit instructions @ 240 MIPS (120 MIPS each)
      • Bus width: 192-bit (96-bit each; 64-bit SDRAM, 32-bit SRAM)
    • Tilemap engine: Sega System 24 tilemap engine
  • Graphical features: Gouraud shading, hidden surface, Z-buffering, point sampling, bilinear filtering, trilinear filtering [68]Media:3D-CG System with Video Texturing.pdf
  • Geometric performance: [69]Media:3DGraphicsProcessorChipSet.pdf
    • 800,000 textured polygons/sec, with lighting and flat shading (400,000 per GPU)
    • 490,000 textured polygons/sec, with lighting and Gouraud shading (245,000 per GPU)
  • Fillrate performance: [70]Media:3DGraphicsProcessorChipSet.pdf
    • Rendering fillrate: 190 million pixels/sec (95 million pixels/sec per GPU)
    • Texture fillrate: 190 million texels/sec (95 million texels/sec per GPU)
  • Optional MPEG sound boards:
    • DSB1:
      • Sound CPU: Zilog Z80 (8/16-bit instructions)
      • Sound chip: NEC µD65654GF102
    • DSB2:
      • Sound CPU: Motorola 68000 (16/32-bit instructions)
      • Sound chip: NEC µD65654GF102

List of Games

Model 2

Model 2A-CRX

Model 2B-CRX

Model 2C-CRX



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