(Topic ID: 232419)

MD's guide to using a larger eprom in place of smaller eprom

By maddog14

2 years ago

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    #1 2 years ago

    I have personally searched for the answer on how to use a larger eprom in place of a smaller eprom. I was never able to locate exact instruction or information how to do so. Anyone that referenced this made it so complicated. Consequently, what I have read never worked. So, here is the simple guide :

    For example, you have a 4 meg chip and you want to use it in place of a 2 meg chip. Now you can.

    This guide uses the MCUmall GQ USB Universal Eprom programmer as my example.

    step 1: open up your programmer software

    step 2:open up the rom/bin file you want to use, click open, then click ok on the next box that opens ( notice after you click on open a box opens up. One of the options is file offset. pay attention to that for later)

    step 3: check the buffer tab on the program. look and see what the last buffer line is for offset. For this example, I chose the Funhouse L9 code. The L9 code uses a 2meg eprom (this is larger than the games original code, which used a 1meg chip) Also note, under device, I have chosen to use a 2meg chip.

    step 4: under device, choose the 4 meg chip that you are going to use. Once you select the chip look under the buffer tab again. You will see that now you have twice as many lines of data. Look and see what line your game code ends and what the next line of game code is. We are looking at what the offset says. ( if you need to, reopen the game code you are using) see that my last line of game code is 0003FFF0. My next offset 00040000.

    step 5: For whatever reason, The chips read at the 'back' of the chip first. So if you just burn the file to the chip without changing the offset, the game code will never be read. SO we want to start burning the file to the back side of the chip. That means we must change the offset, this is where the file will begin burning.
    Open up the game file code again. click open. In the box that says file offset, type in 00040000. click ok. That means, this is where the game code will start burning.

    step 6: click write. the game code will then burn to eprom ( no need to double burn as some have suggested, which I never got to work)

    This should work on any chip.
    If you have any question, just message me

    open file (resized).JPGfile offset (resized).JPGbuffer 2meg (resized).JPGgamecode offset choice (resized).JPGfinal offset (resized).JPG

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