TSROM advice/guidance?

Greetings everyone!

I decided to make a TSROM conversion with sockets. Unlike NROM, TSROM seems to be a bit more complex.
I am confused about the PRG and CHR roms.

I have Bo Jackson Baseball, the PRG is 28 pin, the CHR is 32.
I have 27c256's.

I noticed the PRG has 4 extra pads on the board like a 32 pin rom would work there.

So my question is, would a 28 pin rom work for both PRG/CHR?
If I socket the board for 32 pin rom, but use 27c256s for instance, would that work?

Or do I need 27c040 for CHR for it to work?

Thanks, it is greatly appreciated.

For a proper TSROM cart you should use a game that got 32 pins for both, CHR and PRG.

Rewire like this:
PRG socket:
Bend up pins 1, 2, 24, 30 and 31
Solder pin 2 to hole 24 (A16)
Solder pin 24 to GND (OE)
Solder pin 30 to hole 1 (A17)
Solder pin 31 to hole 2 (A18)
CHR socket:
Bend up pins 1, 2, 22, 24, 30, 31
Solder pin 2 to hole 24 (A16)
Solder pin 22 to hole 31 (CE or CHR /A13)
Solder pin 24 to hole 2 (OE or CHR /RD)
Solder pin 30 to hole 1 (A17)

Only a very few games use less than 64kb CHR, so 27c010 / 27c020 or 27c040 are your way to go in any case to make sure everything works.

All NES cartridges with ROMs larger than 64 KiB used this pinout.

Famicom cartridges manufactured by not-Nintendo with ROMs larger than 64 KiB used the standard pinout instead.


Do be careful; a 27C256 only holds 32 KiB.

I see, so a 28 pin PRG is isolated to fewer titles in comparison.
If you wanted to repro Bo Jackson Baseball, could you use 27c010/20/40 on PRG socket?
because I intend to install 32 pin sockets, although I lack the proper IC at the moment.
I havent looked at any PRG or CHR files to determine size. Just got a tsrom board and sockets.
I probably should have done that eh? ;D

Thank you both for the info, the shared knowledge is really appreciated. As well as the link to pinout. That will be helpful. : D