Thursday, February 23, 2017

Fujitsu MB86233 "TGP" DSP

In this post we look at obtaining the Fujitsu MB86233 ROM for the following:
  • #14 Sega 315-5571
  • #15 Sega 315-5572
  • #16 Sega 315-5573

 First decap a sample chip to get more information.  Here's 315-5571:

Which tells us it's contact programmed:

Under 20x brightfield illumination:

Our computer vision expert was concerned automatic capture would be noisy and asked for a 100x die scan.  Unfortunately, 100x takes a long time.  Fortunately, a quick test showed a 20x scan with crossed polarizers has sufficient SNR:

We then fed this into computer vision tools like on 39.  Finally, ROM bit order was swapped around until it disassembled relatively cleanly.  Unfortunately, instruction set documentation is incomplete meaning even correct bit ordering may produce disassembler errors.

Chips around #211 - 218 are suspected to be similar chips and we might take a look at them in the near future.

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To be clear, 14-16 were all decapped and captured (gotta catch'em all!)

#14 Sega 315-5571:

#15 Sega 315-5572:

Similar to above, but takes up slightly more code space.

#16 Sega 315-5573:

This one uses basically all of the code space.  There's also minor overglass delamination in two spots.  Here's the worse one:

Unclear what caused this, but fortunately bits are not obscured by it.  If they were, could probably be removed with brief HF wash.


  1. For those interested, these chips are all used by Virtua Racing. Specifically, 315-5571 and 315-7752 are geometry-related programs we don't understand yet, and 315-7753 is the coprocessor program initially simulated in model1.cpp and nowadays replaced by the Daytona USA TGP program.

    The code seems to be essentially correct, and shows you current TGP understanding is far from complete (the only good documentation is in japanese, and doesn't have opcode encoding...). This is going to help.

    The geometry-related programs are common to all model 1 games. The copro isn't, Virtua Fighter's is 315-3724 and Star Wars Arcade/Wing War/Net Merc is 315-5711. Sadly, caps0ff has neither of these two.

    Chips 211-218 come from model2 boards, where they'll be very useful for model 2/2a emulation.


    1. I probably have a scrap board with 315-3724 on it....

    2. well you'll have to talk nice to CAPS0ff because it's their call. I am ready to send that chip and probably others (8751/68705) if they ask me.

    3. actually it's 315-5724. I am holding the VF board in my hand right now....

    4. Guru I recognize these from your site, love your work! I'm always excited when there is commotion in the model1 emulation world. One of my fav hardware besides the Namco System 21.

    5. Hi CAPSoff,
      Guru has two M68705P5 CPUs that I sent him to decap.
      Could you please accept the Slapfight A76 and Return of the Invaders CPUs that I sent Guru for decapping.
      Regards, Ting.

  2. hats off to you guys at capsoff ! bet you not heard that before. lol but seriously great to have you all on board with the emulation decryptions. Great work !!

  3. Wow !!! Finally proper Model 1 emulation possible ! Thanks !

  4. Amazing work can't wait for 211-218 to be processed.

  5. the post wasn't clear, were all three processed or just #14?

  6. Any more news on this? has any info been able to get from decapping the chips?

    1. A small update: other TGPs are decapped, imaged, and digitized. We've been busy with real life and need to find some time to check and push them out. If people are anxious we could push them out, knowing they will probably need more correction / reimaging

    2. I recently got a Wing War 315-5711 board to attempt a Star Wars conversion of a VF boardset, but it would be fun to see emulation of awesome stuff like Netmerc/Star Wars come to fruition. Would this be of use to you Caps0ff?

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  8. Please decap chip 315-5724 for Virtua Fighter, 315-5711 for Star Wars Arcade, Wing War and Netmerc coming soon.