First post! EPROM Substitutions and Pinout Confusion?

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

Moderators: B00daW, Moderators

Post Reply
milkmanv1
Posts: 2
Joined: Fri Apr 07, 2017 7:53 am

First post! EPROM Substitutions and Pinout Confusion?

Post by milkmanv1 » Fri Apr 07, 2017 8:08 am

Hey all,

First post here, I float around from forum to forum, and wound up here. Why you ask? Well nes repro's of course! Just got my ebay eprom programmer, and fixed up my copy of Lagrange Point to play in english and replaced the save battery. I'm sure that all you guys here know that soldering can end up like potato chips, and you're always looking for stuff to keep your hands busy.

Now I know Lagrange Point is an easy one, just one ROM chip to solder over with the Konami IC having the same pinout as a M27c4001. Which leads me to my 2 questions.

I know I've stumbled across a list of Eproms that also displays the factory mask rom chip numbers and shows good "substitution chips" Now I know as 32PIN 512KB eprom chips the pile of M27c4001 chips I already have could be used if I double up or quadruple up my CHR and PRG files to make them work on the larger chip. But I plan on making like 10 or more repros and I would honestly rather just get some 128KB and 256KB chips in addition. I doubt I'll be making too many 28pin repros but we'll cross that bridge when I get there. At any rate, I can't seem to find said list of EPROM compatibles anymore, so if anyone knows what I'm talking about/ could just name some EPROMS that I should have on hand to make repros/translations as I go then that would be awesome.

Second, I don't know too much about this, which is why I am here and asking for your guidance oh mighty hackers! Pinouts! I know that Lagrange Point is an unusually simple case. Most games have 2 mask roms and most require jumping a few pins, which kinda splits into two questions.

I've seen the pinout databases/guides on the wiki, and I know "if the pins on your eprom don't read the same, lift and jump" however....can someone provide a little bit of a tutorial on exactly how thats done..? Is it a matter of (just for example) if pin 19 is A8 on the mask rom, and A8 is actually pin 5 on the eprom, thats where you lift and jump?? I've only been looking at games which have established write-ups on what chips to use and what/where to solder, so I'm a bit confused on how one can "figure it out themselves" as I want to make english translations of my famicom carts of Radia Senki, Fire Emblem and Sword Master which there are not explicit write-ups for.


The final subquestion here, is over on romhacking theres a program which will scramble the pinout of a chip...has anyone used this with any success? For example, Final Fantasy 3 requires only 1 512kb 32pin chip. Part of the reason I got 10 M27c4001's - also I got them for like...3$ shipped. ANYWAY. I know that if you use that EPROM you need to lift and jump exactly 3 pins. If you use the eprom pinout re-mapper, does it actually work to write the Binary to the eprom, but change the way that the information is written so that no pins have to be jumped (even on a factory board doing a 1-1 swap?)

THANK YOU GUYS YOU ALL ROCK.

Sorry I know thats a lot, just excited to be making my own repros.

Ice Man
Posts: 546
Joined: Fri Jul 04, 2014 2:34 pm

Re: First post! EPROM Substitutions and Pinout Confusion?

Post by Ice Man » Sat Apr 08, 2017 1:58 am

Welcome and hi there.

For NES/FC Repros you usually really only need EPROMs from 27c256-27c080.

27c256, 27c512 are used commonly in NROM/CNROM as well as Color Dream games.
27c010, 27c020, 27c040 are mostly used in MMC1/MMC3 games, however, you can use 27c010/27c020 in UxROM games as well with some rewiring.
27c080 is mostly used in MMC5 games.

Last not least, some notes I got and expanded with my knowledge about rewiring EPROMs to work with NES PRG/CHR.

Code: Select all

NROM (mapper 0):
No modifications nessesary


CNROM (mapper 3):
No modifications nessesary


CNROM 32 Pin EPROM (mapper 3):
Bend up pin 1, 2, 3, 30, 31 and 32
Solder pin 30 to hole 28 (+5V)
Solder Pin 31 to hole 28 (+5V)
Solder Pin 32 to hole 28 (+5V)


UNROM (mapper 2):
Bend up pin 24
Solder pin 24 to GND (OE)


UNROM 32 Pin EPROM (mapper 2):
Bend up pin 1, 2, 24, 31 and 32
Solder pin 2 to hole 22 (A16)
Solder pin 24 to GND (OE)
Solder pin 30 to hole 28 (+5V) <- Bend up only when game larger than 128KB (UOROM)
Solder pin 32 to hole 28 (+5V)


SNROM (mapper 1):
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)


SNROM -> SUROM Conversion (mapper 1):
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)
Cut track from MMC1 pin 11 to WRAM pin 20
Solder pin 31 to pin 11 of MMC1 chip (A18)
Solder pin 20 of WRAM to Ground (CE (E1) or CHR /A13)


SLROM (mapper 1):
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)
CHR socket:
Bend up pins 1, 2, 22, 24, 30 and 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)


SGROM -> NROM conversion (mapper 2 to mapper 0):
PRG socket:
Bend up pin 22
Solder pin 22 to GND (OE)
CHR socket:
Bend up pins 27 and 28
Solder pin 27 to pin 14 (GND)
Solder pin 28 to pin 28 (+5V)
CHR ROM conversion:
Desolder MMC1 completely
Solder pin 21 to hole 16 of MMC1 (CIRAM A10) - for H-Mirroring
Solder pin 23 to hole 16 of MMC1 (CIRAM A10) - for V-Mirroring
Solder MMC1 hole 1 to MMC1 hole 21 (PRG A14)
Solder MMC1 hole 5 to MMC1 hole 20 (PRG /CE)
Solder MMC7 hole 7 to MMC1 hole 15 (CHR A12)


TKROM & TSROM (mapper 4):
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)


TKROM -> TKSROM conversion (mapper 4):
Bend up MMC3 pins 10 and 12
Solder a wire from MMC3 pin 12 (CHR A17) to MMC3 pad 10 (CIRAM A10)


TKROM -> TNROM conversion (mapper 4):
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 RAM conversion:
Seat the RAM chip 2 pins back (pin 1 of RAM is pin 3 of socket)
Bend up pins 1, 20, 22, 26 and 27
Solder pin 1 to hole 30 (+5V)
Solder pin 20 to hole 31 (CE or CHR /A13)
Solder pin 22 to hole 2 (OE or CHR /RD)
Solder pin 26 to hole 28 (+5V or RESET)
Solder pin 27 to NES pin 56 (CHR /WR)


ExROM (mapper 5):
PRG & CHR socket:
Bend up pins 1, 2, 24, 30 and 31
Solder pin 1 to hole 30 (A19)
Solder pin 2 to hole 24 (A16)
Solder pin 24 to hole 31 (OE)
Solder pin 30 to hole 1 (A17)
Solder pin 31 to hole 2 (A18)
CHR RAM conversion:
Seat the RAM chip 2 pins back (pin 1 of RAM is pin 3 of socket)
Bend up pins 1, 22, 26 and 27
Solder pin 1 to hole 32 (+5V)
Solder pin 22 to hole 31 (OE or CHR /RD)
Solder pin 26 to hole 32 (+5V)
Solder pin 27 to FC pin 47 (CHR /WR)


UNROM -> AOROM conversion (mapper 7):
Bend up pins 1, 2, 24, 30 and 31
remove '32 chip
cut track to pin 6 of '161
Solder pin 2 to pin 13 of '161 (A16)
Solder pin 18 to pin 6 of '161 (D4)
Solder pin 24 to GND (OE)
Solder pin 30 to pin 12 or '161 (A17)
Bridge gap between pins 10 and 11 where '32 was (A14)
Bridge gap between pins 3 and 13 where '32 was (A15)
remove solder gap for either V or H
Solder NES pin 22 (CIRAM A10) to pin 11 of '161


UNROM -> UOROM conversion (mapper 2):
Bend up pin 6 of 74HC161
Bend up pins 9 and 10 from 74HC32
Connect pin 9 from 74HC32 to pin 2,5, or 12 of 74HC32 so all 4 are connected together.
Connect pin 11 of 74HC161 to pin 10 of 74HC32
Connect pin 6 of 74HC161 to D3 of PRG ROM
Connect pin 8 of 74HC32 to A17 of PRG ROM


MMC3 -> Mapper 245 conversion:
Disconnect MMC3 PPU A10,A11,A12 IN, tie all three to ground.
Disconnect MMC3 CIRAM A10 OUT from CIRAM A10 IN, tie CIRAM A10 IN to PPU A10 (vertical mirroring / horizontal layout).
Disconnect MMC3 CHR A10, A11, A12 OUT.
Connect CHR RAM A10, A11, A12 directly to PPU A10, A11, A12.
Connect MMC3 A11 OUT to PRG ROM A19.


Panesian -> CNROM Conversion (mapper 3):
Bend up pin 5 and 12 of 74HC161
Connect pin 5 to D2 of PRG ROM
Connect pin 12 to A15 of CHR ROM


Chinese Game Fix:
Lift CHR ROM /OE Pin and connect it to Famicom cartridge connector pin 17.


Sunsoft 5A/5B:
PRG socket:
Bend up pins 1, 2, 24, 30, 31 and 32
Solder pin 2 to hole 22 (A16)
Solder pin 24 to GND (OE)
Solder pin 30 to pin 32 of FME-7 (A17)
Solder pin 31 to hole 28 (+5V)
Solder pin 32 to hole 28 (+5V)

One Screen Mirror:
MMC3 Pin 10 lifted.
CIRAM A10 to GND.
I personally have never used the EPROM Pin Swap tool by Farid yet but plan to give it a chance one day.


Good luck!

User avatar
TylerBarnes
Posts: 17
Joined: Tue Mar 19, 2019 12:41 pm

Re: First post! EPROM Substitutions and Pinout Confusion?

Post by TylerBarnes » Mon Mar 25, 2019 11:13 pm

I'm working on an UNROM board. Have a bunch of 27C512 chips around (28pin) . would these need the wiring suggested here? pin 24 to GND? Not really 100% on what chip this re-wire was meant for. I beeped it out and Pin 24 on the 27c512 is A9 rightly going to NES cart pin 4.
Last edited by TylerBarnes on Mon Mar 25, 2019 11:39 pm, edited 1 time in total.

lidnariq
Posts: 9510
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: First post! EPROM Substitutions and Pinout Confusion?

Post by lidnariq » Mon Mar 25, 2019 11:21 pm

27C512 only holds 64 KiB; few games have exactly that much PRG. (For whatever reason, NES games usually had 32 or 128 KiB of PRG, but largely skipped 64 KiB).

You may be better served either ignoring half the capacity, or making a multicart.

For 28-pin sockets, the NES pinout matches the standard; you probably won't have to do any rework. See nesdevwiki:Mask ROM pinout

User avatar
TylerBarnes
Posts: 17
Joined: Tue Mar 19, 2019 12:41 pm

Re: First post! EPROM Substitutions and Pinout Confusion?

Post by TylerBarnes » Mon Mar 25, 2019 11:42 pm

lidnariq wrote:27C512 only holds 64 KiB; few games have exactly that much PRG. (For whatever reason, NES games usually had 32 or 128 KiB of PRG, but largely skipped 64 KiB).

You may be better served either ignoring half the capacity, or making a multicart.

For 28-pin sockets, the NES pinout matches the standard; you probably won't have to do any rework. See nesdevwiki:Mask ROM pinout
The program I'm working with is my own, so 64kb is suitable. Thank you for the resource.

User avatar
TylerBarnes
Posts: 17
Joined: Tue Mar 19, 2019 12:41 pm

Re: First post! EPROM Substitutions and Pinout Confusion?

Post by TylerBarnes » Tue Mar 26, 2019 1:44 am

Looks like pin 22 on the 27C512 is in the same spot pin 24 would be on the 27C010 so wiring pin 22 to GND is sort of working on console. Though my program is pretty broken now. Not sure if just more wiring error or something else. *Scratches head*

Post Reply