Sega System 16B ROM board conversion

Pelly22

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So I have already successful de-suicided a Golden Axe board, so I am familiar with putting on a generic 68000 CPU and re-flashing the required EPROM's with the un-encrypted ones.

What I wanted to try and work out is if I can convert a particular ROM board (I.e. Flash Point) to an Altered Beast board. I know some games vary with the amount of Rom's used, however I was hoping I could just flash the required Altered Beast ones with the un-encrypted Rom's.

Has anyone done this before?
 
If you look up the mame driver for Sega 16 games that will give you all the info you need including the switch settings on each rom board and what rom boards are usable with what game

hope that helps
 
If you look up the mame driver for Sega 16 games that will give you all the info you need including the switch settings on each rom board and what rom boards are usable with what game

hope that helps

This was the only driver info I could find, some of the other sites seem to be down. Anyway this looks like it might have what I need. I will check out my ROM boards and see if they are compatible.

https://github.com/groovybits/groovymame/blob/master/src/mame/drivers/segas16b.c

If you know of any other resources that would be helpful, please let me know.

Thanks
 
So I noticed that a number of the ROM's on this board are write once only mask ROM's. What would be the equivalent EPROM I could use on these? The ROM's that are currently used are Toshiba TMM24512AP-20 and the ones I want to burn for this particular Altered Beast set are 64kb images.

Thanks
 
So I noticed that a number of the ROM's on this board are write once only mask ROM's. What would be the equivalent EPROM I could use on these? The ROM's that are currently used are Toshiba TMM24512AP-20 and the ones I want to burn for this particular Altered Beast set are 64kb images.

Thanks

TMM24512AP-20 are equivalent to 27(C)512
 
I will leave this information here just because it was mostly working in this form - however there are graphics glitches I was never able to overcome through adjusting the jumpers, if someone has more luck, hopefully they will let me know so I can update this thread with the information to make it work 100%


Pelly sent me his boardset so I could give him a hand getting this up and running so I thought I'd do a small write-up to explain a couple of the pitfalls of this particular conversion.

The MAME driver needs updating with a lot of the jumper settings for various games, and the decrypted MAME ROM set listed in the driver for use on this board is missing the sound ROMs which must then be obtained by downloading the parent set and burning those onto the correct size ROMs.

If the jumpers are incorrectly set it will certainly not boot and worst case scenario will destroy the ROMs inserted on the board, so I think it's worth talking about how to do this properly.

NB: The ROM board used for this conversion is a 171-5704 type - other games that use this board type are:

Bay Route
Golden Axe
MVP
Aurail
Flash Point
Wonderboy III
Cotton
Wrestle War
Riot City
Tetris

To perform the Altered Beast conversion you will require:

17x 27C512 EPROMs for object, sprite and sound data
1x 27C256 EPROM for sound program data
7x 27C1000 EPROM for main CPU, scrolling background and speech data

There are 2 ROM sets you will need to download to get the correct EPROMs

Altered Beast Set 5 (317-0069) - This has all the ROMs including the decrypted main CPU code required to run the game

Altered Beast Set 8 (317-0078) - This has the sound program ROM at A10 and speech data ROMs at A11 and A12 that are missing from the set above. This set requires the 8751 CPU that the board I'm using does not have, so we use the above set which was designed for the FD1094 encrypted CPU.

Install the EPROMs in their correct locations on the board (the MAME naming convention tells you the correct sockets to install everything so there shouldn't be any need for me to put that information here)

Here is a picture of the fully populated board in case anyone wants it as a reference

https://www.dropbox.com/s/sthx0pjdvxjl5rc/File 20-2-17, 19 21 49.jpeg?dl=0

You will then need to set the jumpers - I worked out by downloading several of the MAME sets that use this ROM board that Bay Route uses almost exactly the same size ROMs for all parts of the board. It does however use smaller sound ROMs than Altered Beast uses, where Aurail uses the same size sound ROMs but larger object ROMs.

These were the jumpers I shorted on the Altered Beast board to get it to run:

S2 - S3 - S5 - S7 - S9 - S11 - S13 - S15 - S17 (this may get adjusted after I do a test run with the board in a cabinet to confirm any issues, but these settings are safe and the board does boot with these jumpers shorted and there does not appear to be any issues)

It's also worth mentioning if you want to set up free play as I did, set all Dip Switches on SW1 to the on position, and if you want Attract Mode sound, set Dip Switch 2 on SW2 to the On position.

Enjoy! :)
 
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Turns out I have to update this one. I thought the game was running ok but there's sprite issues with the projectiles in particular, and when I solved that problem, there were issues with other sprites around the place.

This particular ROM board supports tile banking and some of these jumpers likely enable that across various sections of the board. Without knowing which jumpers do what, unfortunately I can't get any further with it.

The only real way to get this going would be to find someone with an original Altered Beast who has this ROM board who can let us know what jumpers they're using.
 
Honestly I never saw or came across an Altered Beast on 171-5704 ROM board but only on 171-5521.I'm wondering if this is not a mistake of MAME source.Indeed, if you read the ROM loading structure of the Altered Beast Set 8 (317-0078), it's reported to run on 171-5521 and not on 171-5704 like stated at the beginning of driver .
 
Thanks caius, I'm running it at the moment so I believe it's definitely capable of working properly with the correct jumpers - it's 90% perfect as it is now just with small glitches

Makes it hard when there is no documentation anywhere I can find on what the jumpers on this ROM board do other than the main CPU code ROM size at S1/S2
 
Use your multimeter in continuity beep mode and see where jumpers go, in tis way you can figure out their functions.
 
I started doing that - but I don't fully understand what I'm looking at, two of the jumpers connect the power rail I assume to different pins for non JEDEC pinout ROMs, others are shorted in order for the game to function but don't seem to actually be connected to anything at all.

I assume what I'm looking for is the jumpers connected to the LS139 and LS138 ICs on the ROM board as it sounds like this is what I'm looking to do from the information I found here:

https://segaretro.org/Sega_System_16B_hardware_notes_(2003-01-12)

So I guess I need to figure out which jumpers enable and disable which outputs on that IC?
 
Ok I've worked out where all the pins from the HC139 go to on the ROM board

Pin 1 -> S15, S16
Pin 2 -> S3, S4, S17, S18
Pin 3 -> S3, S4, S17, S18
Pin 4 -> S3, S4, S17, S18
Pin 5 -> S3, S4, S17, S18
Pin 6 -> S13
Pin 7 -> ROM B13 Pin 22
Pin 8 (Ground)
Pin 9 -> ROM B12 Pin 22
Pin 10 -> ROM A2 Pin 22
Pin 11 -> ROM B10 Pin 22
Pin 12 -> ROM B8 Pin 22
Pin 13 -> ROM B7 and ROM B3 Pin 22
Pin 14 -> ROM B2 and ROM B6 Pin 22
Pin 15 -> All ROM Pin 16
Pin 16 (Vcc)

So far I know:

Pins 6, 4 and 5 are the Enable lines
Pins 1, 2 and 3 are my Select inputs
Pins 15 through to 7 are my outputs
Jumpers S4 and S18 are directly connected to the +5v rail or possibly ground? Pin 8 of the HC139 also seems to be connected here and that should be a ground pin, yet the Vcc line is connected up to the same rail.
Jumper S16 is connected up to jumper S3 - unsure of why this would be the case

And from looking at EPROM pinouts I know that Pin 22 (Pin 20 on a 27C512) is the enable line for the EPROM.

I need to work out if the jumpers are attached to any other functions on the board I guess. I don't understand why 2 of the enable and 2 of the select inputs are connected to 4 different jumpers.

Edit: Realized I was looking at an LS138 not a 139, 138 is a multiplexer which makes sense given the application.

Edit again: Next step I think is to work out which jumper controls which enable lines and select lines for the outputs. ROM position B13 is unused so this can be disabled while all other positions are populated.

I believe the problems are occurring due to bus contention at the 2 output pins where 2 ROMs are connected but I'm unsure as to whether this can be resolved.
 
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After playing with this some more I've had to come to the conclusion (as caius suggested would be the case) that this will only run with one set (317-0078 set 8 I think it's listed as) - MAME correctly lists this number as the correct version for the board, however the EPROM numbers listed are incorrect for this set.

I burnt the 317-0078 set and installed it on the board and it ran perfectly graphically, however would not coin up, start a game in free play or play any sound due to the missing MCU which sadly has not been dumped and may never be (The Guru has it listed on his site as undumpable at least for now) as it requires the chip to be destroyed (decapped) in order to read the code and a second one must also be found/destroyed in order to confirm the code is correct so that it can be recreated.

The decrypted code is for the version of the game that runs on 512kbit ROMs rather than 1mbit and I was unable to get the jumpers to get the game to run on this board. In spite of this being the same board as the 171-5521, there is obviously a difference somewhere which I can't get around.

There are 3 versions of Altered Beast that run on 1mbit ROMs that could potentially be used. None of these have been decrypted for one reason or another

317-0065 (FD1094) - Wanted by the MAME team, not found as of yet

317-0066 (MC-8123B) - Dumped but not verified with a second dump or released by DWidel, possible errors towards the end of the data

317-0078 (8751) - Listed as currently undumpable by The Guru

So unless these MCUs can be found and decapped, I don't think it's possible to make a "decrypted" version of this MAME ROM set to run on an original board. I'll leave the information I've found so far here so that in case others find a way around the issues I've had, they can hopefully update the thread and let us know :)
 
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