JOTEGO
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Ajax
🕑 Added 2025-07-04 16:20:43 +0000 UTCThis week's release updates the beta key. Please remember to copy the new one to your MiSTer/Pocket FPGA.
History
This game, released by Konami in 1987, features a unique mix of 2D vertical-scrolling and 3D-scrolling stages. In the 2D stages, players pilot the ultra-fast attack helicopter TOM TRIGER, while in the 3D stages, they control the jet fighter >, working to stop a nuclear superpower and an alien army from joining forces to create a space-based nation. The background behind the creation of this game in the success of Taito’s Twin Cobra at the time, which inspired Konami to develop its own take on the combat helicopter genre. Simultaneously, on a separate team, development was also underway on a 3D jet fighter game inspired by Sega’s After Burner. However, both projects ran into creative roadblocks during development. The teams struggled to expand the stage variety, and as a last-ditch solution, the bold decision was made to merge the two games into one.
It was a popular game, but since this was the first Konami arcade board to use flat-pack ICs, it often suffered from malfunctions. The leads of ICs and LSIs would lift off the PCB traces due to vibration or temperature changes.
Types of Power-Up Items
When you destroy a red enemy formation, a power-up item appears and slowly descends while cycling through the following icons: V → B → 3 → T → L. The effect depends on which icon is showing when you collect it, so quick judgment is required to grab the one that best suits the situation.
VULCAN – Increases rapid-fire capability. You can control its firing direction with the joystick.
BOMB – Ground attack weapon. Enhances shot speed and destructive power.
3WAY – Fires in three directions: straight ahead and to both sides simultaneously.
TRIPLE – A forward-facing three-way shot.
LASER – Fires two powerful laser beams straight ahead.
OPTION – Appears after destroying all red enemies in a formation. Adds an option unit that mimics your main ship's attacks.
Technical Insights
The game shows several effects of smooth zoom and rotation of large elements:
the game logo
the big cloud in the airplane dive stage
the big ship boss
These effects are made with a chip called K051316. Furrtek reversed engineered it a long time ago. This core is the first one to use that information. In order to understand how the chip works, let's look first at a regular tilemap system:
A RAM memory controlled by the CPU contains a list of tiles to draw on the screen. There is a one-to-one relationship between each RAM memory address and each 8x8 pixel block on the screen. The hardware reads the memory and based on its contents, it draws an 8x8 block from the graphics ROM memory on to the screen. the video memory is read as the CRT screen is refreshed: from left to right and top to bottom in a linear, straight way. The readout is made with two counters, one counts the screen column currently visible and another one counts the row. These are the horizontal and vertical counters. The horizontal counter is increased once per pixel and reset after each line ends. The vertical counter is increased once per line and reset after each frame ends.
Konami's 3D chip works by making these two counters independent from the screen. Imagine that we increase the horizontal counter less than once per pixel. Then by the time a full line has been drawn on the screen, the counter has still not reached the end count. If we use that counter to readout the memory, this has the effect of reading that memory more slowly, making the drawing appear larger on screen as real pixels have been moving at its usual pace whereas the counter has been moving more slowly. Thus, by changing the pace of the counters we can shrink and enlarge the drawing on the screen. By changing the initial position of the counters we can make the drawing move around the screen (scroll).
And the most interesting effect: if you add an additional step to the horizontal counter each time a new line begins (rather than just counting each time a new pixel is drawn) then the memory is read on a diagonal line, creating a rotation effect. In summary, rather than reading the memory left to right, top to bottom at the same pace than the screen is drawn, the chip allows the memory to be read at different paces and with an angle.
Although all the games using this chip seem to use only these effects, if the CPU changes the counter parameters at the beginning of each line, it would be possible to create the same effects we see on Super Nintendo Mode 7 games. This can be made by adding a horizontal line interrupt to the CPU driving this chip. However, Konami implemented this on their next chip (K053936) by using an internal RAM with per-line data. This RAM can be updated by the CPU once per frame, rather than line by line, so it frees up the CPU.
The K053936 is the chip used on Run & Gun, so you can see now how Ajax links with our core development road map.
Known Issues
The analogue video output may show some garbage at the screen borders. This is not visible on the MiHDMI/Analogue Pocket outputs. MAME cuts off the video width to 304 pixels whereas we are showing 320 pixels. We believe that is the reason. We may clip the video on the following update to prevent this.
Patreon Update
Today’s release marks the 9th consecutive week of new games and cores, and the 19th release of the year. That means we’ve shipped content in 7.5 out of 10 weeks so far—pretty solid momentum!
We’ve also continued supporting the open-source community by publishing our work and contributing to the MAME project whenever possible.
On top of that, we’ve expanded the range of systems we support, including light gun games and more. What’s next?
For the second half of 2025, we’re aiming to bring support for Run & Gun and CPS3, and to finish ongoing open betas like System 18 (just a couple of games missing) and Neo Geo Pocket Color (still ironing out game saving and some compatibility issues).
There will also be new hardware releases tied to these systems—plus a few surprises along the way. We want to hear from you!
Are you enjoying the current content? Is there anything you feel is missing or want to see more of?
Let us know your thoughts about the project and the scene—we read every comment and your input really helps shape what’s next.
Comments
David Pushpanathan
Better late than never! Thanks Jotego and team for all the hard work, really enjoying it :) My votes- Space Harrier, Afterburner, Mortal Kombat 2 and NBA Jam. Those classics are desperately missing. Hopefully in the next decade- Taito F3, PGM, Sega System 32, Namco System 11,12,22, Konami 573, Capcom ZN-2 and lastly Sega Model 1/2(!)... Thanks again!
Mat Azel
A bit late but it just came to me, Hyper Duel would be super awesome to have too, great shmup and hard to come by these days👍
Josh Parker
IDK if I'm too late to make a suggestion, but Frogger is a classic we don't have on the Analogue Pocket yet that would be cool.
Videodr0me
Love it! But i think there is a small cosmetic bug in the new framework. If you rotate the screen, Scandoubler fx is greyed out. You can still use for example HQ2 (which i like for most games) if you first set rotate screen to no then choose HQ2 under scandoubler fx and then afterwards set rotate screen to yes.
Matthew Belshan
I would love to see the arcade game Quarth from Konami. Also excellent output for all the cores that have been coming. Great work!
