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Sega CD

Discussion in 'Technical Discussion' started by Devon, Oct 7, 2022.

  1. That's not really true at all IMO Sadly the Mega CD didn't get enough PC point & click ports and most of the FMV games either came from old Laserdisc games or were built for the Mega CD itself.
    And what did you expect CD-ROM to offer at that time? It's hard to think of PC CD-ROM Dos games that didn't do anything different from the floppy version, other than add voice-overs and FMV. Why people expected the Mega CD to be so different, I do not know .

    PC's were super expensive in the 90's and out of the reach of many, that's why in the UK at least we had the big uptake in micro computers and btw the Mega Drive had a number of watered down PC ports, not that it really mattered. Star Flight and Buck Rogers are some of the best games you can buy on the Mega Drive IMO
     
    Last edited: Dec 12, 2022
  2. Devon

    Devon

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    Today on "what is this nonsense?", I present this:

    [​IMG]

    ...what is this nonsense?
     
  3. Brainulator

    Brainulator

    Regular garden-variety member Member
    It seems to me like it's saying "don't go crazy with FMVs".

    I like how they misspelled "quite" as "quiet" at one point.
     
  4. Devon

    Devon

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    But, they make it seem like it's the Genesis VDP's fault that video cannot be full screen with a smooth framerate, when that's not exactly the full truth. Yeah, the VDP has its limitations with VRAM space and data transfer bandwidth, but those aren't egregious enough to really prevent a smooth fullscreen video. On the Genesis alone, lack of ROM space just makes that unrealistic. With the Sega CD, you have RAM and disc reading limitations that prevent an adequate amount of data from reaching the Genesis in time to really get a smooth video in full screen. The comments about color count and resolution are just dumb, and the comments regarding the graphics operations(??) are just plain gibberish to me here.

    Get used to it, the manuals are filled with typos and bad grammar.
     
    Last edited: Dec 20, 2022
  5. MarkeyJester

    MarkeyJester

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    The comments on colour and resolution are to do with horizontal sprite limit, they're implying plane A and B would display the first two palette lines, and sprites filling up the entire H40 range would display the third line. Another line of sprites (for the fourth line) cannot be layered on top due to the horizontal limit, and they're suggesting to cut the motion image horizontally in half so two sprite layer's worth can overlay, allowing all four lines to display in every 8x8 space.

    You can garnish 16fps (3 frames per render) on a 50Hz Mega Drive system, transfering a full H40 screen worth of tile graphics, but on a 60Hz system, you're lucky to get 12fps (5 frames per render), with no processing of any data, just direct DMA transfer during V-blank periods. 12fps is considered bearly acceptable for human motion portrayal, though the minimum tolerable perceived motion is said to be 24fps. The human eye is complex and isn't a camera, so it's quite subjective, but from what I've seen, 16fps is considered smooth enough, but 12fps just isn't enough, and tricks have to be used to hide it. These transfers are for a single layer of tiles too, and multi-layer would cost more transfer time, and more VRAM space, only a single layer of H40 tiles can fit into VRAM at any one time, which is perhaps why they were suggesting 38x24 ($7200 bytes of VRAM for double buffer and space left for plane mappings).

    So the blame cannot be placed solely on ROM space limitations, video smoothness and colour range are still issues even with unlimited ROM space. It's true the Mega CD has its own limitations, but they're not wrong about the Mega Drive's role in the issues. Also, a side note, it's the Mega Drive's fault the contacts for the expansion slot are coating in Aluminium which is a poor conductor, and probably didn't help the data transfer rate.
     
  6. Devon

    Devon

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    Okay, yeah, that makes a lot more sense. The wording of the manual definitely threw me off, BUT I also completely forgot to take into account the cost of additional layer data AND forgot about the sprite limit, because what I had in my mind was single layer videos that had different tiles using different palette lines. That's completely on me, so my bad. Interesting tidbit on the contacts on the expansion slot, too.

    As a side note, I saw this thread on SpritesMind that was posted back in 2017 that mentioned JVC X'Eye service manuals, and how they actually document the CDD command and status codes. Thought it was interesting.

    [​IMG]
    [​IMG]
     
    Last edited: Dec 21, 2022