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Thread: EPROM inserted wrong way | Mega CD 2 bios

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    EPROM inserted wrong way | Mega CD 2 bios

    What is your experience as regards to inserting an EPROM the wrong way into the socket - does it always result in instant death for the EPROM?

    The EPROM is a n AT27C1024 for Mega CD 2 region free bios. After getting rid of the old bios and installing a bios socket I dicked up and put the bios in the wrong way - tried it a few times but just got a black screen. Then noticed my mistake, put it back in the correct way but still just a black screen.

    I ordered another one, but since I cut my stock bios out and desoldered the remains I don't have a bios to test with at the moment to verify whether its the region free bios that got fried or whether its another problem altogether. I don't have an EPROM programmer to verify the chip contents or burn a new one myself.
    Regards, MtothaJ

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    From what I understand any eprom thats put in the wrong way is toast.

    Hope you have not done any damage to anything else though!!

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    Quote Originally Posted by titchgamer View Post
    From what I understand any eprom thats put in the wrong way is toast.

    Hope you have not done any damage to anything else though!!
    Thanks for the response, that is my understanding also. This one appears to be a one-time programmable type since it does not have the erase window but would imagine that same principal applies.
    I will probably have to wait a week or so before I get the new bios to test. Fuse did not blow, voltage regulator is outputting the correct voltage so there is hope.
    Regards, MtothaJ

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    Quote Originally Posted by MtothaJ View Post
    What is your experience as regards to inserting an EPROM the wrong way into the socket - does it always result in instant death for the EPROM?

    The EPROM is a n AT27C1024 for Mega CD 2 region free bios. After getting rid of the old bios and installing a bios socket I dicked up and put the bios in the wrong way - tried it a few times but just got a black screen. Then noticed my mistake, put it back in the correct way but still just a black screen.

    I ordered another one, but since I cut my stock bios out and desoldered the remains I don't have a bios to test with at the moment to verify whether its the region free bios that got fried or whether its another problem altogether. I don't have an EPROM programmer to verify the chip contents or burn a new one myself.
    I don't think anything else will damage by putting the EPROM upside down. It is death to the EPROM because the opposite corner pins are usually +5 and GND, so if you put it the other way, it will get -5v (+5 to GND and GND to +5V) which will break it.

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