nesdev.org

I want to make a reproduction of final fantasy II nes and I see that I need to use a snrom board to do this. I'm confused because the board only has a prg chip. How are both the prg and chr files used to get this game up and running with only one chip?

Game uses CHR-RAM and programs the CHR-RAM from the PRG side of the cart basically.

zeda wrote:I'm confused because the board only has a prg chip.

The board certainly has a CHR chip, but it's not ROM, it's RAM. In these cases you leave the CHR-RAM chip alone, and replace only the PRG-ROM chip. The game program itself will take care of writing the patterns it needs to the CHR-RAM chip as the game runs.

Since we are on the topic of Final Fantasy II, I had a question regarding my reproduction of the game. It seems kinda glitchy and I don't know why.

When i instert the cartridge, I have to hit reset for it to load and then until I press start, the game goes in and out of garbage and the correctly displayed screen.

Does this sound familiar to anyone?

One quick question, if you have a copy of Final Fantasy 1, are you able to turn this into a Final Fantasy 2 cart?
How easy would this be?

Vorde wrote:One quick question, if you have a copy of Final Fantasy 1, are you able to turn this into a Final Fantasy 2 cart?
How easy would this be?

Here is the writeup I used to make my first SNROM dev cart.

http://www.54.org/sage/condev/ff2cartproject/

The only changes I would make are to the parts list...
* 2megabit EPROM 27C020 or 27C2001 (see below)
* access to an EPROM burner (see below)
* access to an EPROM eraser

I would replace this with...
* SST39SF020A-70-4C-PHE (easier to find than older 27, 28 & 29 parts)
* GQ-4X USB programmer

If you just want a copy of FF2, you could probably find someone to make you one for a small fee. I have a few spare Ultima carts that could be used for this. But if you'd like to have a dev cart and the ability to re-write it, either get a chip programmer like the GQ-4X or go with a PowerPak.

lordloss wrote:Since we are on the topic of Final Fantasy II, I had a question regarding my reproduction of the game. It seems kinda glitchy and I don't know why.

When i instert the cartridge, I have to hit reset for it to load and then until I press start, the game goes in and out of garbage and the correctly displayed screen.

Does this sound familiar to anyone?

Are you talking about the modified intro graphics glitching during palette fades? Discussion about that problem, fixes, and so on are here: http://nesdev.com/bbs/viewtopic.php?p=79764#79764

I'm reading forum for a while and I like it very much:) Wanna make my first repro cart so I need a little help...
For FF2 repro cart you need to replace PRG-ROM chip (on donor cart SMB2), I'm interesting in wiring the chip, can someone who actually did this made a diagram or post it if he has one? Thank you:)

SNROM is NOT an MMC3 board. Any MMC1 board will do as long as it has all the pins, although games with CHR-RAM built in already would be easier to work with.

You'll want battery-backed WRAM as well.

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Sorry I didn't double check the ROM type, you're right. But still I don't know how the wiring goes. I found a pic on net but it's not clear so I couldn't decipher it

Ok, done a little more research, so basically I have NES Open Tournament Golf cart, and that's a good start. From the details I saw of the game, is it possible just to change Mask ROM with FF2, no wiring? And one technical question about EPROM's, I should be using 27C020/2048kB (256k x eight), but which one? 100ns/120ns or 150ns, or it doesn't matter?
Thanks

SnakeNS wrote:From the details I saw of the game, is it possible just to change Mask ROM with FF2, no wiring?

Anything larger than 32KB needs rewiring on the NES. I don't have the exact instructions to give you, but it's really just a matter of comparing the pinouts of the Nintendo mask ROMs vs. the EPROM/Flash you'll be using and rerouting everything that doesn't match, cutting traces and lifting pins as you see fit.

Nintendo ROM pinouts can be found here. The pinout for your memory chip of choice can be found here. Plan everything carefully on paper beforehand, based on the pinouts.

And one technical question about EPROM's, I should be using 27C020/2048kB (256k x eight), but which one? 100ns/120ns or 150ns, or it doesn't matter?

I believe that the NES works with chips as slow as 200ns... so everything you listed is OK.

@tokumaru
Thank you for your effort, I think I'm starting to understand a little better So for example, I choose 2-Megabit 256K x 8 OTP EPROM, and then start to compare...the pins that are not matching must be bend and properly rerouted. I will try to do the plan but could you just tell me what rules should apply, I mean what is MUST NOT connect. (I'm not in programming)
I assume that the 1,2,31,30,24 are the pins that I must change/reroute.

PRG ROM - 256KBytes (32pin):


PRG A17 - |01 32| - +5V
PRG /CE - |02 31| - +5V
PRG A15 - |03 30| - +5V
PRG A12 - |04 29| - PRG A14
PRG A7 - |05 28| - PRG A13
PRG A6 - |06 27| - PRG A8
PRG A5 - |07 26| - PRG A9
PRG A4 - |08 25| - PRG A11
PRG A3 - |09 24| - PRG A16
PRG A2 - |10 23| - PRG A10
PRG A1 - |11 22| - PRG /CE
PRG A0 - |12 21| - PRG D7
PRG D0 - |13 20| - PRG D6
PRG D1 - |14 19| - PRG D5
PRG D2 - |15 18| - PRG D4
GND - |16 17| - PRG D3



2-Megabit 256K x 8 OTP EPROM (32pin):

VPP - |01 32| - VCC
A16 - |02 31| - PGM
A15 - |03 30| - A17
A12 - |04 29| - A14
A7 - |05 28| - A13
A6 - |06 27| - A8
A5 - |07 26| - A9
A4 - |08 25| - A11
A3 - |09 24| - OE
A2 - |10 23| - A10
A1 - |11 22| - /CE
A0 - |12 21| - 07
O0 - |13 20| - 06
O1 - |14 19| - 05
O2 - |15 18| - 04
GND - |16 17| - 03

A good way to learn what works where is comparing the pinouts of a 32KB mask ROM against a 32KB EPROM, because those are known to work without any rewiring.

By doing that I can see that VPP works when connected to +5V, /PGM to GND, and /OE to /CE. If those connections work for the smaller chip, they will surely work on the larger chips too.