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I'm using baseball as my donor cart for Balloon Fight but its not working. I burned bf's prg file to a 27C512 and stuck it in the socket then I got treeted to a nice gray screen. I checked the solder by sticking the baseball rom back in and it worked. Then I dumped the baseball prg chip, erased the 27c512 (erasable winbond ), burned it, verified it, loaded it then marveled at gray. From what I've read the pin outs are the same for 27c512's and 32k prg chips. What am I doing wrong?

Thanks

Did you replace both the PRG & CHR Mask ROM's with sockets for EPROM's? If you are using an EPROM with larger capacity than needed (27C512 = 64K, Balloon Fight Mask PRG Mask ROM = 32K) don't forget to ground the unused address pins. For instance if you are just burning the lower 32K of the 27C512 then ground pin 1 or A15. If you are burning the first 8K of a 27C512 for the CHR ROM then ground pins 1,26 & 27 or address pins A15, A13 & A14. Otherwise the NES might be looking at blank memory (0xFF).

Thanks for the reply.
I only have two eproms and I only wanted to risk one so only the prg is socketed. I assume everying is low/high format (damn assembly) so then I burnt to the upper 32k and its looking at the lower? How would I know and what should I ground? Or how would I wire up a switch for two 32k games?

Skidlz wrote:Thanks for the reply.
I only have two eproms and I only wanted to risk one so only the prg is socketed. I assume everying is low/high format (damn assembly) so then I burnt to the upper 32k and its looking at the lower? How would I know and what should I ground? Or how would I wire up a switch for two 32k games?

Just "double up" the ROM to fit the EPROM... so if the EPROM's 64K, double the 32K ROM up to make it 64K. you can do this in DOS:

copy /b filename+filename output.bin

that will double up "filename" and save it to output.bin.

Also, is baseball on an NROM128 board or NROM256 board? If it's an NROM128 board, it won't work no way no how since those are only set up for 16K of ROM. Dunno why nintendo did that, but they did. A14 is missing on NROM128 boards. You might be able to add a wire, however, if the finger is there on the cart edge.

kevtris wrote:Also, is baseball on an NROM128 board or NROM256 board? If it's an NROM128 board, it won't work no way no how since those are only set up for 16K of ROM. Dunno why nintendo did that, but they did. A14 is missing on NROM128 boards. You might be able to add a wire, however, if the finger is there on the cart edge.

So, there's a way to put a 32k eprom to work on a board set up to 16k?
Because I got a Baseball to make a devcart too, and with this limitations I will not be able to put 32k PRGs on there...

Can you explain where exactly A14 goes?
There are any chances to make this work properly with socketed eproms?


Thanks.

Its 128 and it has no a14. Its connected to +5 and I now realized I soldered my switch to +5 . But baseball does have a full set of 72 fingers and I can probably wire pin 14 to any of those. What does pin 14 do and why would they allow 32k of rom? Sorry of thats a noobish question.

Thank you

Why does the A14 pin double the address space? Answer: Fourteen address lines numbered A0 through A13 can specify up to 16,384 (2^14) distinct addresses. Adding A14 makes 15 address lines, which can specify up to 32,768 (2^15) addresses.