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Thread: Sega CD system specs

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    Systemwars vs Sega-16 Master of Shinobi gamegenie's Avatar
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    Default Sega CD system specs

    I saw this here. It looks accurate enough

    Main CPU: Motorola 68000 @ 12.5 MHz
    * Same as the Genesis... runs in parallel with it... except the Genny
    CPU runs at the slower clock speed 7.9 MHz

    Graphics Processor: Custom ASIC

    RAM:
    * 6 Mbit Main RAM
    - Program
    - Picture
    * 512 Kbit PCM Waveform Memory
    - Wavefile memory
    * 128 Kbit CD-ROM data cache memory
    * 64 Kbit Internal Backup RAM

    Colors:
    * Originally 64, same as Genesis
    * Using programming tricks, can get 128 colors via HAM ("Hold and
    Modify")
    - Originally developed on the Commodore Amiga to boost color
    capabilities
    - Basically a graphic over a graphic = a double-color
    * Using Cinepak and TruVideo:
    - 128 to 256 colors
    - Increase screen size from 1/4 to full
    - Advanced compression scheme, used in Win 95
    - Software-based upgrade
    * Eternal Champions CD uses 256 colors simultaneously (only game to
    do so)

    Storage capability of a Sega CD
    * Approximately 500 MB of data (62 min of audio data equivalent)
    * 1/4 screen B/W footage video: 1.5 to 4 hours
    * 1/4 screen color footage: 45 minutes
    * Above specs are prior to compression

    Transfer rate of Sega CD: 150 kbytes/sec (Single Speed)

    Boot ROM:
    * 1 Mbit, contains:
    - CD Game Bios
    - CD Player Software
    - CD+G Software

    Bios versions:
    * When you start the Sega CD, the title screen displays the Bios
    version in the upper-right corner of the screen. This helps
    identify what machine version you are using and in a way the
    security capabilities. (Startup music and startup screen of the
    Sega CD is different for each Bios)

    Bios Version Machine
    1.00 Original Mega CD
    1.10 Original Sega CD, Motorized Drive
    2.00 Mega CD2
    2.05 Sega CD2
    2.10 Sega CD2

    CD Access time: 800 ms

    Sound Circuitry:
    * PCM Sound Source
    - Stereo, 8 channels
    * 32 KHz Maximum sampling wavelength
    * 16 Bit D/A converter
    * 8X internal over-sampling digital filter

    Audio characteristics:
    * Frequency Range: 20Hz - 20 KHz
    * Signal-to-Noise Ratio: >900dB@1K
    * Channel Separation: >900dB

    Output: RCA Pin Jack x2 (L/R)

    Dimensions: 301mm (w) x 212.5 (d) x 112.5 (h)

    Weight (Sega CD1): 3.1 lbs / 1.4 kg

  2. #2
    Mastering your Systems Hero of Algol TmEE's Avatar
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    there's no such thing as "hold and modify" on MD, there's quite a bit of inaccuracies and things in the list that are not really hardware related.
    CDs can contain 650MB of data IIRC.
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    Zebbe's Avatar
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    That Eternal Champions statement on it using 256 colours is false AFAIK. There is no mention of the scaling/rotation chip, or is it the ASIC?
    Got Pier Solar? Good. Please post a comment here.

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    ESWAT Veteran Chilly Willy's Avatar
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    Quote Originally Posted by Zebbe View Post
    That Eternal Champions statement on it using 256 colours is false AFAIK. There is no mention of the scaling/rotation chip, or is it the ASIC?
    It is indeed the ASIC. In the specs, under Colors it should simple delete all the lines except the first: same as Genesis. Also, it has the Genesis CPU speed wrong, it's 7.67 (NTSC) or 7.60 (PAL), not 7.9 MHz.

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    ding-doaw Raging in the Streets tomaitheous's Avatar
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    If I might add something to the list

    The ISO-9660 format, the SegaCD (be it bios or cd controller firmware) ignores the track Index 01 marker of the first tracker and statically assumes a hard sector offset of 150 sectors (2 seconds). I was able to exploit this in make a CD that booted both on the SegaCD and the Turbo Duo (it was Lords of Thunder, single CD plays the game on both systems). Just thought that was interesting that they used a hard offset system instead of grabbing the sector offset of track Index 01.

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    Systemwars vs Sega-16 Master of Shinobi gamegenie's Avatar
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    Quote Originally Posted by Zebbe View Post
    That Eternal Champions statement on it using 256 colours is false AFAIK.
    I wonder if Eternal Champions: Challenge from the Darkside was programmed with 256 colors, even though 192 of them would never be seen through the Genesis.

    Unless....unless you play it with the 32X attached. Erika!

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    ESWAT Veteran Chilly Willy's Avatar
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    Quote Originally Posted by gamegenie View Post
    I wonder if Eternal Champions: Challenge from the Darkside was programmed with 256 colors, even though 192 of them would never be seen through the Genesis.

    Unless....unless you play it with the 32X attached. Erika!
    More likely, it was merely dithering, like many other games.

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    Hero of Algol kool kitty89's Avatar
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    Yeah, the video formats do to "increase" colors on screen is to use dithering. (which you won't notice in composite video)

    Although I have heard Puggsy on MD/MCD actually displays added colors somehow, it's come up a couple times in some old threads, not sure how it was done, but apparently it was CPU intensive.


    On the CD-ROM storage, I think the "500 MB" refers to the common LD format discs used, I beleive these are also sometimes referred to by other capacities such as as 550/560 MB, though I don't think theres a "standard" naming for the LD CD's. http://en.wikipedia.org/wiki/CD-ROM Accorining to wiki, this format actually holds 580 MB of data. Also, "650 MB" = 682 MB, "700 MB" = 737 MB, "800 MB" = 829 MB, and "900 MB" = 912 MB. (and ~15% more audio data can be stored on all of these)


    There's a lot wrong with other stuff in that article too. Like for the Saturn it says the SH2's are 50 MIPS each (which would mean they were superscalar...), when they're 25 MIPS each. And I'm pretty sure the CD-ROM cache should be 512 kbits (64 kB), not 512 kB.

    And the polys/s ratings are high with the Saturn's being the "ideal" maximum, and the PlayStation's being the very exagerated.
    Last edited by kool kitty89; 05-08-2009 at 08:24 PM.

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    Joe Redifer's Avatar
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    Quote Originally Posted by kool kitty89 View Post
    Yeah, the video formats do to "increase" colors on screen is to use dithering. (which you won't notice in composite video)
    I sure as hell did. I played my Genesis in composite video since I purchased it up until only a few years ago, and every time I looked at a game like Eternal Champions CD in composite I thought to myself "Ewwww, this game is one dithery mess. Nasty!"

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    ESWAT Veteran Chilly Willy's Avatar
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    Yeah, it was RF that made the dithering work, not composite... unless your TV filtered the hell out of the chroma signal.

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    The Gentleman Thief Baloo's Avatar
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    Quote Originally Posted by Chilly Willy View Post
    Yeah, it was RF that made the dithering work, not composite... unless your TV filtered the hell out of the chroma signal.
    Yeah, but composite wasn't really even totally integrated until the Dreamcast era, and they were still selling RF switches to go with those systems.

    A lot of TVs back in the early-to-mid 90s didn't have composite output. So I would assume programmers would try to make the game look as well as it could using the RF switch rather than composite cables.
    Quote Originally Posted by j_factor View Post
    The Sega Saturn was God's gift to humanity. This is inarguable fact!
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  12. #12
    Systemwars vs Sega-16 Master of Shinobi gamegenie's Avatar
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    Quote Originally Posted by Baloo View Post
    Yeah, but composite wasn't really even totally integrated until the Dreamcast era, and they were still selling RF switches to go with those systems.

    A lot of TVs back in the early-to-mid 90s didn't have composite output. So I would assume programmers would try to make the game look as well as it could using the RF switch rather than composite cables.
    Most TVs that were less than 19" inches didn't have it. But the larger sets did, some even had the S-Video and 480i component inputs.

    I always thought Sega included AV with Saturn, they didn't? Sony and Nintendo did with the PSX and N64 during those times.

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    Hero of Algol kool kitty89's Avatar
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    I think it depends on the model too, I've head some of the Model 2's (and probably the VA-7 M1) have poor composite output, the ealr M1's are supposedly pretty good.

    Many low end (even pretty large) CRT TV's only had RF imput, I see lots of these at the locak good will stores. Growing up my family had a 27" Sony Trinitron from arround 1991, composite and S-video. (it finally died ~5 years ago)

    It's a bit odd, but some of the newer lower-end flat screen CRT's and LCD's have composite and component jacks but no S-video!
    Last edited by kool kitty89; 05-08-2009 at 11:00 PM.

  14. #14
    ESWAT Veteran Chilly Willy's Avatar
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    Quote Originally Posted by Baloo View Post
    Yeah, but composite wasn't really even totally integrated until the Dreamcast era, and they were still selling RF switches to go with those systems.

    A lot of TVs back in the early-to-mid 90s didn't have composite output. So I would assume programmers would try to make the game look as well as it could using the RF switch rather than composite cables.
    Yeah, my Genesis Model 2 came with the RF adapter only. The composite cable was separate. My first TV with composite inputs was probably about 1992-ish. I used an RF switchbox that came with my Atari 400 to switch between the Atari and the SEGA.

    Somewhere around 1998, I switched to RGB on my old Amiga 1084 monitor. The jump from RF to RGB was startling.

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    Joe Redifer's Avatar
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    Quote Originally Posted by gamegenie
    I always thought Sega included AV with Saturn, they didn't? Sony and Nintendo did with the PSX and N64 during those times.
    Yes, it did and no RF was included. My Sega Master System included both RF and AV as did my model 1 Genesis, unless my brain has been destroyed by tons of meth. Maybe it was just the SMS that had both.

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