Archive for December, 2015

One of the great things about having a fully merged MAME/MESS project is that it gives exposure to some things that might otherwise be missed.

plgDavid recently picked up (for the costly price of 600$) the last remaining undumped Casio PV1000 game cartridge, a port of Universal’s Lady Bug known on this platform as Fighting Bug.

The PV1000 was a simple system and received basic but original ports of a handful of arcade classics from around the period it was sold.

There isn’t really a huge amount I can say about the game, it’s Lady Bug, it plays a decent game, if you didn’t have access to an arcade then it would have been a nice piece of software to have at home back in the day. I’m glad to see it’s been preserved.

Anybody familiar with the MAME emulation of various Gaelco games will know that the big stumbling block for a many of them is the DALLAS DS5002FP security / suicide chip present on a lot of the PCBs.

In fact the only reason the game World Rally is emulated at all is because Gaelco directly provided the internal code of the security chip for that game (but no other games unfortunately)

The other working Gaelco sets are all unprotected versions, and even when we have both an unprotected and protected version of a game the protection is so well embedded that trying to simulate it is a nightmare.

We thought we’d actually got all the known unprotected versions of Gaelco games already, that was until system11 spotted an unprotected version of ‘Glass’ with an additional ‘Version 1994’ subtitle displayed on the title screen. Naturally he picked it up to investigate further.

The board has PROMAT stickers on the program roms, and the pictures of girls used ingame have been replaced with Anime drawings, no nudity. It looks very much like this version was created for the Korean market, presumably a year later than the original release when protecting it wasn’t considered such a high priority. The PCB lacks any of the components relating to the security.

As this version is completely unprotected it runs fine in MAME

Eco Fighters is a shooter released by Capcom in 1993, it can be seen as a spiritual successor to Forgotten Worlds in that it’s a horizontal shooter with a rotatable character.

One little known fact about the game is that it supports Spinner as an input device, however this configuration was exceedingly rare in the wild and for a long time it was thought a special romset was needed in order for the spinners to function. As a result most people are used to playing the game with a Joystick which doesn’t give anywhere near as precise control, especially irritating to players of the game was the fact that the attract demos were clearly recorded with an analog device (a Spinner).

As it happens no special romset is required at all, an otherwise unused bit in the input ports specifies that the Spinners should be used, and by feeding the correct analog inputs with that bit set the game plays as it was meant to be played.

This discovery actually came to light as a result of 3rd party spinner kits that were being sold for use with the game, allowing it to operate with Forgotten World style controllers. While the official Capcom spinner kit for the game is very rare (and thought to possibly have only been used on location tests) the unofficial kits are actually fairly easy to get hold of, and to our surprise didn’t require any kind of modified romset to function.

These kits prompted me to take another look at the game code, with the new knowledge that when the spinner is plugged in it should change the display of the test menu to show ‘Rolling’ instead of the P2/P3 buttons. I was able to quickly located the bit controlling this, and from there the pieces fell into place. The problem before was that we were looking for a way to enable a test mode control type option for the Spinner (like Puzz Loop 2 has) but it seemed like if there ever was one it had been removed from the code leading me to conclude that the versions we had no longer supported a spinner, I’m glad to have been proven wrong over this!

I can only assume the spinner for the original is rare due to cost cutting at Capcom, anybody who has played this with a Joystick, or attempted to play Forgotten Worlds without the spinner (using a keyboard / joystick in MAME, or on some stupid multi-game arcade setup without the proper controls) will tell you that it’s not an enjoyable experience, many spots in the game rely on you being able to make fast and precise movements to snipe down enemies.

Here’s a quick video of the game running in MAME with spinners (best watched at 60fps to get a good idea of the smoothness of the movement)

In the comments of my update about Nostradamus an original reference video for another game I’d emulated a long time ago was posted. That game was Aquarium by Excellent System, the video was this one by YouTuber ‘zu4989’

The post was made in relation to an audio issue in the emulation, now, the driver was done long before I really had any idea how to hook up audio chips, so that side of thing was done by somebody else (R. Belmont from memory?) but with a better understanding of these things myself now I decided to take a look.

The basic issue was that the wrong music was being played at the wrong times.

Initially I thought it might be a simple case of a bad modernization, old versions of MAME required you to leave a gap in the CPU region where you loaded a ROM if RAM was present for 8-bit CPUs (Z80 etc.) Newer versions don’t have this flaw and as a result a lot of drivers were cleaned up to remove that hack and handle things properly, it looked on the surface like the rom loading on Aquarium had been updated, but the modernized banking code was pointing to the wrong places (it was looking for 7 banks of 0x8000 from an offset of 0x18000 in the z80 region, which actually exceeded the size of the region and could have potentially caused crashes if the final banks were actually banked in)

However, even fixing that, the music did NOT match the reference videos provided.

Looking more closely at the banking writes the game was making revealed a little more, we were using the bottom 3 bits of the register, so writes of 0x00, 0x01, 0x02 … up to 0x07 would select different banks. What the game was actually writing was 0x0, 0x1, 0x2, 0x3 and 0x10, 0x11, 0x12, 0x13, nothing else. At this point it was clear that we were using the wrong banking bits, the correct bits to use were the bottom 2 bits, and the 4th bit.

Each bank contains a difference piece of music, so by cross-referencing with the video again I was able to establish which bank write related to each real bank, and re-order the above bank select bits into the proper bank value (bit 0x01 -> 0x01, bit 0x10 -> 0x02, bit 0x02 -> 0x04) with that done, the music was fixed. This scrambling isn’t too surprising, the driver already had a descramble function for the OKI commands.

I’ve recorded a video of the game with the correct music being played, (CHEATS ARE ENABLED TO MAKE DEMONSTRATING ALL THE LEVELS EASIER) You can cross-reference it with the video linked above if you want

The reference video also showed a number of cases where our priority handling wasn’t correct, namely the top border should have been chopping the large fish sprites and wasn’t, the large fish sprites also needed to go under the insert coin text (already correct) but at the same time needed to be shown above the bottom part of the NEXT text. Furthermore the smaller sprites showing the next pieces to appear needed to go underneath the tilemap. All those cases were fixed. The background colour was also incorrect, this wasn’t really visible anywhere except on the Winners Don’t Use Drugs screen, but I fixed that while I was at it as it was obvious even without a reference.