Thunder Cross, Space Odyssey and Keyboard Support on the Pocket

Thunder Cross

JTALIENS core gets support for one more game: Thunder  Cross. This is a spectacular shooter with a good depth feeling thanks to  the use of parallax scrolling and sprite scaling. As in Nemesis, you  get options to fly along your ship. These options can either shoot with you or use a special shoot, depending on the powerups you get.

This game works on almost the same PCB as last week's Gang Busters, except for an additional chip: the 052591.  This is a programmable coprocessor. It is only used in three games, as  per MAME's documentation: Thunder Cross, S.P.Y. and Hexion. Nobody knows  how it works. The main CPU writes a large number of bytes to it, and  then the chip does its business. What it is know, is what the main CPU  is expecting from it, which is different for each game.

For Thunder Cross, the CPU uses this coprocessor as a  collision detector. For each frame the CPU writes two lists of hit boxes  and reads back which ones from each list collide each other.

I do not consider FPGA conversions to be emulators, as in  general, the cores are just a re-design using a different technology.  But the 052591 is a good example of emulation because  we do not know what the original design is, so we cannot redesign it. We  are emulating some aspects of its behavior in an educated way. However,  the rest of the system in this core is not emulated but redesigned.

Furrtek, who does schematic extraction from decapped custom chips, has expressed interest in researching the 052591.  As with other projects in the past, part of your Patreon contributions  will go to sponsor his work. Access to beta cores is what gets many  people into Patreon, but what they are really paying for is all the  research and maintenance we do.

This might be the last game this core sees, so it is approaching the publishable status after a long 6-month development period.

Space Odyssey

We have completed a small PCB that implements SEGA's custom chip 315-0042, used in Space Odyssey. The design follows SEGA's original schematics. This will help repair broken boards.

The KiCAD project files are in the jtcores repository.  If you'd rather get an already built board, we needed to repair 3 PCBs  but we ordered 20 units. Send a private message if you'd like to acquire  one of them. PCBWay has kindly sponsored part of this development.

I do not have the FPGA core for this system in the short  term road map. If you think this, and other games of the early 80's are  interesting, please say so in the comments.

Core maintenance

• Shaolin's Road set 2 presented corrupted sprites. Reported by GoldZabu. Fixed. Requires new .rom files on Pocket
• Pocket: Added version property to JSON core files
• Pocket: All cores (except for jtbubl, jtdd and jtkunio) updated to support a keyboard when docked. The keys match MAME default controls.  F2 is particularly useful to enter the service menu of some games  (CPS2, Pang...). Note that you cannot control or invoke the Pocket's  settings from the keyboard. That will require a firmware update that can  only come from Analogue. I have requested some changes to the firmware  already, but feel free to mail them yourselves too :-)