Problems with some CD games and Everdrive MD

Discussion in 'Mega Everdrive / Everdrive MD' started by kikendo, Jul 9, 2014.

  1. kikendo

    kikendo Active Member

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    I just got a Mega CD for my Megadrive and am having problems with some games while running the Everdrive.
    I'm using the everdrive to load a regionfree BIOS and boot any game.

    - Snatcher shows no text
    - Wing Commander stuck at intro
    - Jaguar XJ220 black screen

    Now I have read some threads here of other people having similar trouble and it seems that this only happens when the Everdrive is on. I have ran out of CDRs now so I can't try region patching these games to run on the original MCD firmware without the everdrive, but I will soon.

    Does anybody know more about this issue and maybe a possible fix? Those regionfree BIOS are really convenient and I like having my Everdrive on all the time.
     
    Last edited: Jul 9, 2014
  2. kikendo

    kikendo Active Member

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    Well I tried every BIOS combination possible and this still happens. Those games refuse to work.
    It'a shame, I really want to play Snatcher and I seriously don't want to have to desolder the BIOS from my MegaCD to put a physical region free BIOS in it. I suppose I'll have to patch games before burning, if that still works.
     
    Last edited: Jul 10, 2014
  3. kikendo

    kikendo Active Member

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    I can't believe the lack of answers :( Will try my luck somewhere else.
     
  4. pas7680

    pas7680 <B>Site Supporter 2014</B>

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    try the official everdrive forums....
     
  5. kikendo

    kikendo Active Member

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    Which are, where?
    If they are in Sega16 I guve up, as they don't activate my account, ever, for no good reason !!
     
  6. pza

    pza <B>Site Supporter 2012</B><BR><B>Site Supporter 20

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  7. l_oliveira

    l_oliveira Officer at Arms

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    Here's a list of other games I am sure will also fail while Everdrive MD is in use:

    Wonder Dog
    Silpheed
    Sengoku Densyo

    Recently I decided to duplicated the method Everdrive uses to boot the CD BIOS from cartridge slot and I got the exact issues you're complaining about. Remembering this thread I came back with an answer about the whole issue...

    The MEGA-CD hardware have a feature Krikzz is apparently unaware of:

    The MEGA-CD ASIC will remap one 16 bit word of the CD BIOS rom on the interrupt vector region so a game can redirect that particular interrupt for it's own code. The games which broke while EverDrive MD is in use do use the said feature.
     
  8. gladders

    gladders Robust Member

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    I spoke to Krikzz who said he hoped the next iteration of the Mega Everdrive OS should have better CD compatibility. Dunno about the Everdrive MD though.
     
  9. link2rage

    link2rage Active Member

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    why don't just this games on cd (but even then silpheed have some problem)
     
  10. l_oliveira

    l_oliveira Officer at Arms

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    It's a hardware problem. Not software problem. It's trick to bypass the internal BIOS is mapping out a feature of the system which some games use.

    Edit: So I don't see how he can fix it without updating the cartridge FPGA chip.
     
  11. altefore

    altefore Member

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    with my everdrive MD silpheed stalls at movie, snatcher goes to black screen, both load perfectly with jap regionfree bios with my mega everdrive x3.
     
    Last edited: Feb 22, 2017
  12. l_oliveira

    l_oliveira Officer at Arms

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    Mega Everdrive X3 has a hardware fix that allows the CD BIOS to work properly from the cart slot. It has to do with the horizontal video interrupt, (used for timing control and screen split control) which the older everdrives screw with. One can put the region free CD BIOS on the MEGA-CD unit and not need a new everdrive.
     

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