Welcome to the SEGA SYSTEM-16B 171-5704 romboard conversion guide !
I started researching this last year when I got my SEGA Tetris board - and with some help (mainly from donluca at arcade-projects thanks man!) I managed to successfully convert Tetris to several other compatible games with the 5704 romboard.
Also a huge help for that were the decrypted roms some brilliant people produced (and are now part of MAME romset).
I will try to explain things as simple as possible - it's nothing difficult: burn some eproms, instert them in correct places and make sure the jumpers are set correctly for each game.
I know there is an upcoming multi from Darksoft but tbh you can't beat the cost of a bunch of eproms against buying the multi. I won't argue that a multi is a more elegant solution and you get to play 3-4 more games that the 5704 does not support but almost all good ones can be had for the cost of some chips
[1] So which games are supported?
This is the list of the supported games
Altered Beast
Aurail
Bay Route
Cotton
Dynamite Dux
Golden Axe
Riot City
Shinobi
Wonder Boy III : Monster Lair
E-Swat
Flash Point
Tetris
IMHO the only notable omission is Alien Syndrome that uses another romboard (171-5358) which has different memory mapping than the 5704 one... maybe someone more knowledgeable could convert it to match the 5704 memory mapping, it is something I cannot do.
There is also Tough Turf but that uses the optional protection MCU and there is no deprotected version that I know of.
[2] Basic Requirements:
- you need a System16B board with the 5704 romboard - Tetris is the perfect game for this
- you need to have normal 68000 and Z80 cpus on your board - store the original Hitachi cpu modules somewhere safe
- you need a programmer to burn your new romsets
- you need to use NON-JEDEC 128kbyte eproms - only then will the games work correctly.
- 256kbyte, 64kbyte and 32kbyte eproms are normal JEDEC ones meaning bog standard 27C020 / 27C512 / 27C256 ones
- in conclusion: burn, match eprom placement and jumper settings and play! nothing more to it!
[3] About the NON-JEDEC eproms:
SEGA has hardwired the romboard to work with NON-JEDEC eproms for the 128kbyte sized ones.
That type was the normal one back then, the only difference from a normal 27C010 is two pins swapped: pin 2 and pin 24.
JAMMARCADE.NET expains the situation here: https://www.jammarcade.net/1mbit-eprom-confusion-jedec-vs-non-jedec/
It is possible to patch the romboard so you can use normal 27C010-style eproms but that is just too annoying IMHO.
Personally I bought a 100pcs lot of MBM27C1000A-15Z eproms and they work great. Other compatible eprom models can be found in jammarcade's list:
So to recap, you need normal standard 27C020 / 27C512 / 27C256 eproms but 128kbyte files need to be burned on NON-JEDEC 128kbyte eproms like the ones on the above list.
[3] Placement of eproms and files naming for burning:
This is the 171-5704 romboard:
it has 2 rows where you can put eproms, top row "A" and bottom row "B".
Both rows have 16 positions as seen on the above pic.
Positions A9 , A13 and B9 are not populated.
When you download the "SEGA System16B 171-5704 rompack.zip" you will find a bunch of directories and inside them the files you need to burn:
so what you need to pay attention is the extention of the file: I have marked epr-12385.a14 in the picture, this means the rom you will burn needs to placed at position A14.
Also you can see it is a 128kbyte file and it needs to be burned on those NON-JEDEC eproms.
Further down the list there is the epr-12524.a5x file, the x just means it's a decrypted rom that does not need the special cpu to run. So it goes to position A5.
For Golden Axe you would need:
6x 27C020 eproms for the 256kbyte files
8x NON-JEDEC eproms for the 128kbyte files
1x 27C256 eprom for the 32kbyte file
[4] Jumper settings:
There are some jumpers on the 5704 romboard in 3 groups marked in blue in the picture above.
You just have to short them correctly so the game works fine , inside each game's directory there is a _jumpers.txt file that explains which jumpers need to be installed.
Basically there is only 2 settings for jumpers:
if a game uses some 256kbyte erpoms: S2 S4 S5 S8 S10 S12 S13 S15 S17 -> CLOSED
all other games that use 128/64/32kbyte erpoms: S2 S3 S6 S7 S9 S11 S13 S15 S17 -> CLOSED
[5] Download link:
Here you can download the "SEGA System16B 171-5704 rompack.zip" file with all the files you will need to burn your new romsets:
https://mega.nz/file/ldVwmIzQ#KZWib8kUsGriUw-cjPBRsDua6a17NgLdDWb3z2GXBPs
https://www.mediafire.com/file/kj23e8ifi9uypd9/SEGA_System16B_171-5704_rompack.zip/file
I hope I did not forget anything
Any questions just ask! I hope this helps someone!
Enjoy!
I started researching this last year when I got my SEGA Tetris board - and with some help (mainly from donluca at arcade-projects thanks man!) I managed to successfully convert Tetris to several other compatible games with the 5704 romboard.
Also a huge help for that were the decrypted roms some brilliant people produced (and are now part of MAME romset).
I will try to explain things as simple as possible - it's nothing difficult: burn some eproms, instert them in correct places and make sure the jumpers are set correctly for each game.
I know there is an upcoming multi from Darksoft but tbh you can't beat the cost of a bunch of eproms against buying the multi. I won't argue that a multi is a more elegant solution and you get to play 3-4 more games that the 5704 does not support but almost all good ones can be had for the cost of some chips
[1] So which games are supported?
This is the list of the supported games
Altered Beast
Aurail
Bay Route
Cotton
Dynamite Dux
Golden Axe
Riot City
Shinobi
Wonder Boy III : Monster Lair
E-Swat
Flash Point
Tetris
IMHO the only notable omission is Alien Syndrome that uses another romboard (171-5358) which has different memory mapping than the 5704 one... maybe someone more knowledgeable could convert it to match the 5704 memory mapping, it is something I cannot do.
There is also Tough Turf but that uses the optional protection MCU and there is no deprotected version that I know of.
[2] Basic Requirements:
- you need a System16B board with the 5704 romboard - Tetris is the perfect game for this
- you need to have normal 68000 and Z80 cpus on your board - store the original Hitachi cpu modules somewhere safe
- you need a programmer to burn your new romsets
- you need to use NON-JEDEC 128kbyte eproms - only then will the games work correctly.
- 256kbyte, 64kbyte and 32kbyte eproms are normal JEDEC ones meaning bog standard 27C020 / 27C512 / 27C256 ones
- in conclusion: burn, match eprom placement and jumper settings and play! nothing more to it!
[3] About the NON-JEDEC eproms:
SEGA has hardwired the romboard to work with NON-JEDEC eproms for the 128kbyte sized ones.
That type was the normal one back then, the only difference from a normal 27C010 is two pins swapped: pin 2 and pin 24.
JAMMARCADE.NET expains the situation here: https://www.jammarcade.net/1mbit-eprom-confusion-jedec-vs-non-jedec/
It is possible to patch the romboard so you can use normal 27C010-style eproms but that is just too annoying IMHO.
Personally I bought a 100pcs lot of MBM27C1000A-15Z eproms and they work great. Other compatible eprom models can be found in jammarcade's list:
So to recap, you need normal standard 27C020 / 27C512 / 27C256 eproms but 128kbyte files need to be burned on NON-JEDEC 128kbyte eproms like the ones on the above list.
[3] Placement of eproms and files naming for burning:
This is the 171-5704 romboard:
it has 2 rows where you can put eproms, top row "A" and bottom row "B".
Both rows have 16 positions as seen on the above pic.
Positions A9 , A13 and B9 are not populated.
When you download the "SEGA System16B 171-5704 rompack.zip" you will find a bunch of directories and inside them the files you need to burn:
so what you need to pay attention is the extention of the file: I have marked epr-12385.a14 in the picture, this means the rom you will burn needs to placed at position A14.
Also you can see it is a 128kbyte file and it needs to be burned on those NON-JEDEC eproms.
Further down the list there is the epr-12524.a5x file, the x just means it's a decrypted rom that does not need the special cpu to run. So it goes to position A5.
For Golden Axe you would need:
6x 27C020 eproms for the 256kbyte files
8x NON-JEDEC eproms for the 128kbyte files
1x 27C256 eprom for the 32kbyte file
[4] Jumper settings:
There are some jumpers on the 5704 romboard in 3 groups marked in blue in the picture above.
You just have to short them correctly so the game works fine , inside each game's directory there is a _jumpers.txt file that explains which jumpers need to be installed.
Basically there is only 2 settings for jumpers:
if a game uses some 256kbyte erpoms: S2 S4 S5 S8 S10 S12 S13 S15 S17 -> CLOSED
all other games that use 128/64/32kbyte erpoms: S2 S3 S6 S7 S9 S11 S13 S15 S17 -> CLOSED
[5] Download link:
Here you can download the "SEGA System16B 171-5704 rompack.zip" file with all the files you will need to burn your new romsets:
https://mega.nz/file/ldVwmIzQ#KZWib8kUsGriUw-cjPBRsDua6a17NgLdDWb3z2GXBPs
https://www.mediafire.com/file/kj23e8ifi9uypd9/SEGA_System16B_171-5704_rompack.zip/file
I hope I did not forget anything
Any questions just ask! I hope this helps someone!
Enjoy!
Definitely up for a few of the titles I don't have! 
