Page 1 of 1

Akira translated cart

Posted: Fri May 22, 2020 10:55 pm
by decoder_82
Hello,

I love to play my favorite games on original hardware. So far I successfully built one translated cart. I am in the process of doing a second one.

I am trying to build a cart with a translation of Akira (Famicom).

From what I see, the games has one PRG rom and two CHR rom:
http://bootgod.dyndns.org:7777/profile.php?id=1561

Orignal roms are as follows:
PRG0 - 128K
CHR0 - 128K
CHR1 - 128K

The three roms are DIP-28

After patching the translation and then using readnes to split I get:

PRG - 256K
CHR - 256K

Luckily PRG will fit on a M27C512 as this is the maximum size on a DIP-28.

My question is what to do with the CHR ?

- How can I check if the patches alter CHR and make it needed to replace the original CHR rom ?

- Should I split the CHR in two and burn the two CHR rom ?

Many thanks!

Re: Akira translated cart

Posted: Fri May 22, 2020 11:06 pm
by lidnariq
decoder_82 wrote:
Fri May 22, 2020 10:55 pm
Luckily PRG will fit on a M27C512 as this is the maximum size on a DIP-28.
512 = kibit, not kiByte! If they genuinely expanded the PRG to 256KB, you'll have to use a 2 megabit 'PROM, which only comes in 32 pin.
How can I check if the patches alter CHR and make it needed to replace the original CHR rom ?
Use some program that can compare binary files, or can tell you the checksum / hash of said files.
Should I split the CHR in two and burn the two CHR rom ?
The purpose of the 74'139 you see on the board is to allow the use of two 28 pin 128KiB ROMs: it both combines PPU A13 and PPU /RD (to generate CHR /OE) but also uses some banking output from the TC0190 to address both ROMs.

If you use a new 2 mega bit 'PROM for CHR, you don't need either of the CHR ROMs or 74'139.

Re: Akira translated cart

Posted: Fri May 22, 2020 11:52 pm
by decoder_82
Many thanks for the reply !
lidnariq wrote:
Fri May 22, 2020 11:06 pm

512 = kibit, not kiByte! If they genuinely expanded the PRG to 256KB, you'll have to use a 2 megabit 'PROM, which only comes in 32 pin.
Thanks for pointing that, you are right.
lidnariq wrote:
Fri May 22, 2020 11:06 pm
Use some program that can compare binary files, or can tell you the checksum / hash of said files.
Indeed SHA-256 are not the same so it is fair to assume I will need to replace the original CHR.

lidnariq wrote:
Fri May 22, 2020 11:06 pm
If you use a new 2 mega bit 'PROM for CHR, you don't need either of the CHR ROMs or 74'139.
Do you mean I can remove from the PCB CHR1 and 74'139 ?

Re: Akira translated cart

Posted: Sat May 23, 2020 10:38 am
by lidnariq
decoder_82 wrote:
Fri May 22, 2020 11:52 pm
Do you mean I can remove from the PCB CHR1 and 74'139 ?
If you use a new 2 megabit PROM for CHR, you must disable both ROMs (by whatever means - this could include tying /CE high, or removing a ROM entirely from the PCB, or removing the 74'139 and tying the /CE pin high from that side)

You could also see if the patch changes only one half of the CHR, and if so, only replace one CHR ROM or the other.

Re: Akira translated cart

Posted: Sat May 23, 2020 5:53 pm
by FrankWDoom
Famirom will split roms to appropriate sizes. DL from here:
http://retro.angelfire.com/kingmercury/

Itll also give you the hash for the chr, you can compare translated vs original rom chrs to see if theyve changed. It wont do halves though, only the whole.

Re: Akira translated cart

Posted: Sun May 24, 2020 3:39 am
by decoder_82
Thanks everyone for the reply.

I have checked and after split the two CHR files have different checksum.

I guess some trials and errors will be needed to make it work.

Re: Akira translated cart

Posted: Sun May 24, 2020 4:49 am
by Ice Man

Re: Akira translated cart

Posted: Sun May 24, 2020 5:46 am
by decoder_82
Ice Man wrote:
Sun May 24, 2020 4:49 am
Or look here: http://forums.nesdev.com/viewtopic.php?f=28&t=14210
Awesome I was searching for a post like this. This should indeed help.