Sega Genesis/Megadrive – Sega/MegaCD – Sega32x hardware Specs.


The mega black beast.

Sega Genesis / Megadrive:

Here you have the specs for the main Genesis/Megadrive console. Strangely, the original manual contains no information on the hardware specifications for the console. I do not know if they are included in later revisions of the manual. However, the Z80 processor present in the original version of the Genesis was later removed in the remodelled Genesis II. The only side effect of the removal is that Master System games cannot be played through the use of the adapter.

Source: Sega Genesis 1 Users Manual, Sega Developer Docs.

  • Model Number: MK-1601 (r1), MK-1631 (r2).
  • CPU: Motorola 68000 at 7.61 MHz
    • 1 MByte (8 Mbit) ROM Area
    • 64 KByte RAM Area
  • Co-Processor: Z80 @ 4 MHz (Not Present in MK-1631)
    • Controls PSG (Programmable Sound Generator) & FM Chips
    • 8 KBytes of dedicated Sound Ram
  • Graphics:
    • 64 simultaneous colors of 512 color pallete.
    • Pixel resolution: 320 x 224
    • VDP (Video Display Processor)
      • Dedicated video display processor
      • Controls playfield & sprites
      • 64 KBytes of dedicated VRAM (Video Ram)
      • 64 x 9-bits of CRAM (Color RAM)
    • 3 Planes: 2 scrolling playfields, 1 sprite plane
  • Sound:
    • PSG (TI 76489 chip)
    • FM chip (Yamaha YM 2612)
    • 6-channel stereo
    • 8 KBytes RAM
    • Signal/Noise Ratio: 14dB

Sega/Mega CD:

Released in 1992, the SegaCD add on to the Genesis was to add a whole new realm of gaming to Genesis owners. The peripheral never achieved major success hoped for by Sega due to its cost, and the lack of any major incentives for purchasing the add on. The extra capacity allowed for much better audio quality and for the use of FMV, just wasn’t enough to attract buyers. Sega launched the peripheral with a campaign dubbed: Welcome to the next level. aka: Welco/Metot/Henex/Tlevel.

The original Sega CD unit used a tray mechanism for the CD, and rested below the Genesis unit. With the launch of the Genesis 2, the Sega CD 2 also appeared. THe SCD2 CD mechanism used the cheaper flip lid. It connected on the side of the Genesis 2, resting next to the unit.

Source: Sega CD1 Users Manual (Part#: 672-0955), Sega Online

  • Model Number: MK-1690 (r1), MK-4102 (r2)
  • CPU: Motorola 68000 @ 12.5MHz
  • Memory:
    • 6Mbit (Program, picture data, sound data)
    • 512Kbit (PCM waveform memory)
    • 128Kbit (CD-ROM data cache memory)
    • 64Kbit (Backup memory)
    • 1Mbit (Boot ROM)
  • Sound:
    • PCM Sound Source:
      • Stereo, 8 Channels.
      • Sampliing wavelength: 32MHz max.
    • D/A Convertor:
      • 16-bit D/A convertor
      • 8x Internal over-sampling digital filter
      • PCM and CD sound mixing.
      • Mixing with mixing terminal possible
    • Audio Characteristics:
      • Wavelength characteristics: 20Hz-20kHz.
      • Signal/Noise Ratio: Over 90dB (1kHz) (Line Out).
      • Stereo channel separation: Over 90dB.
  • Misc.
    • Battery Backup Durection: Approx. 1 month
    • 1x CD-Rom Drive Speed (150kb/s)
    • Audio Out: L/W RCA pin jack.
    • Dimensions (WHD): 301mm x 212.5mm x 112.5mm (r1),

Sega 32x

Released in Fall 1994, the 32x was yet another peripheral for the Genesis. This one promised 32-bit power, and high color graphics. Marketed as a stepping stone to the 32-bit world, and a cheaper alternative to future full 32-bit ssytems, the 32x was doomed to a short life by the lack of decent launch titles, and the impending launch of the Saturn. The 32x was a very expensive failure for Sega. Only 27 32x games were released.

The addon plugged into the cartridge port of the Genesis and connected via various A/V cables. It utilized a cartidge storage system to ensure compatability with existing Genesis titles. It was originally desgined for use on the Genesis 1/2 and CDX. But due to the lack of FCC approval, the devices’ use on the CDX was not marketed/recommended.

Source: Sega

  • Model Number: MK-84000 or MK-84000a.
  • CPU: Dual Hitachi SH-2 RISC Processors @ 23 MHz each, 40MIPS.
  • Co-Processors:
    • Genesis 68000, and Z80
    • Genesis 32X VDP
  • Graphics:
    • 32,768 simultaneous colours on screen
    • Genesis resolution
    • Overlaying over existing Genesis/SegaCD video
    • 50,000 texture-mapped polygons/sec
    • Texture mapping
    • Hardware scaling and rotation
  • Sound:
    • Stereo PCM chip
    • Audio mixing with Genesis sound
    • Additional 2 channels (8 Channels total, or 16 with SegaCD)
    • PSG (TI 76489 chip)
    • FM chip (Yamaha YM 2612)
    • 6-channel stereo
    • 8 KBytes RAM
    • Signal/Noise Ratio: 14dB

2 thoughts on “Sega Genesis/Megadrive – Sega/MegaCD – Sega32x hardware Specs.

  1. The Z80 actually IS in the newer model Genesis, it’s just no longer a separate chip. Sega put both the Z80 and the PSG into the VDP IC to save on costs. SMS games work fine on the newer consoles, but you need a different adapter as the old one didn’t fit the newer consoles – it was a physical problem, not electrical. There are guides online that show how to chop up your adapter to work on the newer consoles if you so desire.

    Also, the rom area for the Genesis is 4 MBytes, not 1. Once you reached 4 MBytes, you needed bank selecting to access more; Sega provided a mapper chip that allowed up to 32 MBytes of rom, but only one game ever used it – SSF2, which had 6 MBytes of rom. Because it was the only game to ever use it, most people call it the SSF2 mapper chip, but it was just a standard Sega mapper used by developers for quite a few years.

    Finally for the Genesis, I don’t know why you include a SNR figure for the sound, which is completely wrong in any case. You should just remove it.

    With the Sega CD PCM chip, you need to change the “sampling wavelength” to sample rate, and the max is 12.5 MHz / 384 (the base frequency divided by the clock steps in the DSP), which is roughly 32.5 kilo samples per second.

    For the 32X, the 32X graphics can be over or under the Genesis/CD graphic, set on a pixel-to-pixel basis. There is no hardware texture mapping, rotation, or scaling. That’s all done using one of the SH2 processors. Sega would probably argue that the SH2 processor is hardware, therefore it’s hardware graphics processing, but that’s just playing with semantics. To anyone not trying to market something, rendering via a CPU is NOT considered hardware graphics processing. The only hardware Sega provided for graphics in the 32X is the ability to shift the graphics one pixel (yes, only one pixel), and a color filler which could write up to 256 words of a solid color to the frame buffer. In one sense, this was good as it meant you were only limited by how good your rendering code was, and in another sense it was bad as it meant you were limited to how good your rendering code was. 🙂

    The 32X sound is PWM, not PCM. It’s a subtle distinction, but important. It was stereo with the ability to use sample rates from 48 kHz. Note that below 16 kHz, you could get aliasing noise in the output (audible on SOME 32X consoles at 14 kHz), and above 40-some kHz, you’re wasting bus bandwidth for no real good reason. 22 kHz was a popular rate at the time, and most games used it. That rate for the PWM channels also meant you could mix four 8-bit samples into a single PWM value without losing any resolution. At 44 kHz, you can only mix two 8-bit samples unless you were willing to sacrifice a bit of resolution (9-bit PWM instead of 10-bit). Again, there’s no specialized hardware to aid in the sound. Just like the graphics, all sound mixing must be done by one of the processors. There’s no QSound hardware in the 32X; all QSound samples were preprocessed and stored in the game rom for playback.

  2. “The 32X sound is PWM, not PCM. It’s a subtle distinction, but important. It was stereo with the ability to use sample rates from 48 kHz.”

    It cut par of that line out, probably because I used less-than and greater than symbols. It should be “less-than 16 kHz to greater-than 48 kHz”.

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