Originally Posted by
Jazzmarazz
Hi Doing it one by one is your problem then. The data becomes broken into the wrong locations and is therefore read back to the Console incorrectly.
Since there are two banks of data with a resolution of 8-bits each, the console must see them as one bank with a resolution of 16-bits.
Here is the way it needs to be programmed:
00000000_00000000
11111111_11111111
22222222_22222222
33333333_33333333
44444444_44444444
55555555_55555555
But it is being programmed like this:
00000000_33333333
00000000_33333333
11111111_44444444
11111111_44444444
22222222_55555555
22222222_55555555
Since the Genesis reads the data one line at a time, you can see that it is not getting it correctly.
What you are going to have to do is trick your programmer. Take note of the tWC and tWP settings used for the 27c040 and tell your programmer you are programming a 27c400. Change the tWC and tWP settings top match the 27c040 and then wire the two ROMs into the programmer like my picture above. By doing this, your programmer thinks it is programming blocks of 16 bits, rather than two blocks of 8-bits.
Just be sure to match up the pinout as you will on the cartridge PCB.