Master Detective

Master Boy is a Spanish quiz game made by Gaelco.

Many years ago Charles MacDonald painstakingly extracted the internal ROM of the HD647180X0CP6 MCU used by Master Boy by exploiting a bug in the game’s string handling to output the internal ROM data, then handfix some bits that couldn’t be accurately dumped that way. This was done before decap techniques were available, so was something of a miracle that any method could be found to dump the rom. I then emulated it with the help of some notes he had made.

What we ended up with was the following game running in MAME

Actually, the above isn’t quite what we ended up with, because prior to last month we were running a set with the copyright message in the startup box hacked out and nobody had noticed, but that’s an aside.

There were however two things that didn’t quite add up here. We had sources that suggested Master Boy was a 1987 game, or possibly even a 1986 game. We also had sources that said there was a ‘Master Boy 2’ from 1991. The PCBs for the emulated Master Boy were marked as revision A, so it was speculated that maybe there was just an earlier set from 1987 we hadn’t found yet, but we’d seen no solid evidence for a ‘Master Boy 2’ at all.

Fast forward to a month or so ago and the guys at ARPA and Recreativas.org uncovered a very different Master Boy PCB

This was clearly not the same hardware as the emulated Master Boy, it’s a much simpler PCB using a Z80 instead of HD647180, an AY8910 for sound, and very little else; it’s a very simple PCB. The PCB was said to be for the 1987 version of Master Boy.

I quickly went about emulating the game, giving me the following.

So that concluded the 1987 version of Master Boy did exist, and was an entirely different piece of code. This newly emulated game is the real ‘first game ever made by Gaelco’ after they split from Tecfri in 1986. It is possible there is still an earlier revision than this as some sources still indicate 1986, but if that earlier revision exists it’s likely to be on this same PCB.

This also very likely means the elusive ‘Master Boy 2’ is in fact just the version we already had emulated, it’s clearly a sequel to this 1987 game, but for whatever reason Gaelco opted to not put ‘2’ on the title screen. Anybody who had played both back in the day would have remembered the 1991 as a sequel, which is where the ‘2’ likely came from.

In semi-related news I’m 99% sure we need to extract the internal ROM from a genuine Italian version of the 1991 game too, the string references on the bootup screen are incorrect using the ROM we have, they seem to be off-by-1, so the startup text here should show ‘Play Mark’ for example, not ‘Mark’ Of course this will require finding a genuine Italian PCB (not one that has simply had the Italian ROMs put on it) and finding a way to dump the internal ROM. With modern decap techniques I imagine there are more options for doing that now than having to resort to the techniques Charles used back in the day tho

Here is a video of the 1987 Master Boy running in MAME

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and here is the original PCB from which it was dumped running

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