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Bomb Jack display hardware

Retro arcade style hardware

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This started life as a working schematic for the video display portion of the original Bomb Jack arcade hardware. The hardware has progressed to add extra features not present in the original.The main project page with dev logs and downloads: https://martin-piper.itch.io/bomb-jack-display-hardwareProteus simulation and PCB design: https://www.labcenter.com/Xinweike PCB manufacture: http://www.xinweikedz.com/

This project started when old retro arcade hardware was being discussed. In the back of my mind was the often fabled "Mega games" by Imagine Software which were planned to use extra hardware on the Spectrum and Commodore 64 to augment the machine's capabilities. Since this hardware uses TTL logic available back from the same time period I was wondering exactly how much extra graphical grunt could have been engineered and interfaced with these old 8-bit computers.

Truth be told, the Imagine hardware was pretty much just extra RAM https://www.gamesthatwerent.com/gtw64/mega-games/ but this was a fun project to see how far the arcade hardware was pushing the limits of board size and signal complexity.

I was looking at Bomb Jack boards on ebay and pondering how they had enough fill-rate to draw 24 16x16 sprites and have the option for some to use 32x32 mode as well. A friend and I were discussing the clock speed and fill-rate while trying to deduce the operation of the hardware just by inspecting the hand drawn schematics, as you do.

In the end to get some clarity on the sprite plotting specifically I started to transcribe what was thought to be the sprite logic portion of the schematic into Proteus, since it can simulate digital electronics really well. More details: https://github.com/martinpiper/BombJack/blob/master/README.md

Work in progress. Donating for the download will help me know which project is popular.

  • Bat and ball game demo

    Martin Piper12/22/2020 at 05:08 0 comments

    This video shows a quick game demo using the video hardware with char and sprites layers.

    The Commodore 64 runs the game logic code and during the vblank send the updates sprite positions to the hardware. This leaves most of the frame time available for game logic processing.

  • Sprites and background screen

    Martin Piper12/15/2020 at 08:22 0 comments

    This video shows the sprites board and background character screen board working together to produce an animated display with two layers. This boosts the graphical capability of the host retro machine, in this case a Commodore 64.

    Each 16x16 pixel sprite can have seven colours with one transparent colour showing the layers behind. Some sprites can also be 32x32 pixels. Some sprites can also be full height, with a repeating 16 pixel vertical pattern. Each sprite has a choice of 32 palettes.

    The character background layer has 1024 characters of 8x8 pixel, with seven colours and one transparent colour.  Each character has a choice of 16 palettes.

    Characters and sprites support horizontal and vertical flips.

    The other two layers are currently opaque pixels and not visible.

  • Testing the faster user port interface

    Martin Piper11/26/2020 at 05:15 0 comments

    This video reviews the delivered components and PCBs, reviews logic analyser tests, and then tests video output on a Commodore 64.

    The user port interface has an auto-increment memory address, which makes it over six times faster than the 4-bit alternating latch prototype user port interface.

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KnivD wrote 12/15/2020 at 15:22 point

Now that's a monster board :)

  Are you sure? yes | no

Martin Piper wrote 12/17/2020 at 01:44 point

It certainly took a while to construct :)

  Are you sure? yes | no

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