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Blogs

Galaxian Part 7 – Preliminary Impressions

September 7, 2021 Retro Ports

Whilst I’ve been waiting for Miro to digest the previous posts and hopefully develop his framework to the point I have described, I’ve actually been doing a little bit of the transcode. I’m not going to go into any specifics here as I’d like to document it in some form …

Blogs

Galaxian Part 6 – Verifying the framework

September 1, 2021 Retro Ports

Before we start on the transcode proper, it would be prudent to test the display output portion of the framework, as this is what we will be using to verify the transcode itself. The purpose is to verify the conversion of the graphics palette, tile and sprite data, the ability …

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Blogs

Galaxian Part 5 – Goals, Aims & Notes on the process

August 31, 2021 Retro Ports

Before we dive into the actual transcode, I wanted to document a few things about the goals and aims of the project, along with some notes about the process. Goals and Aims First and foremost, the aim of the project is to document and preserve both the behaviour and the …

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Blogs

Galaxian Part 3 – Anatomy of an arcade game

August 29, 2021 Retro Ports

Before we can create a framework for the transcoded game, we need to understand the architecture of the original. Every single arcade game that I have reverse-engineered thus far has been driven by the 60Hz VBLANK interrupt. Not only does this allow the game to update the sprites without any …

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Blogs

Graphics formats

August 28, 2021 Retro Ports

The format of the graphics in an arcade game like Galaxian is optimised for the video circuitry rendering the image as the raster beam scans down the screen. Specifically for Galaxian, the graphics data for each bitplane is stored in a separate device (ROM chip) so that colour data for …

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Blogs

Galaxian

August 27, 2021 Retro Ports

A fellow retro enthusiast by the name of Miro expressed interest in the porting (transcoding) of Sean Riddle’s Galaxian dissassembly to a higher level language and asked if anyone was willing to collaborate. Given that the codebase is very similar to Scramble, and the hardware identical, I thought I’d be …

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Blogs

Oh yeah, Scramble…

July 8, 2021 Retro Ports

Well, once you lose momentum on a project when Real Life intervenes, you can very quickly forget about it completely, which is pretty much what happened on Scramble. I must admit, I haven’t even thought about it for several weeks now, only reminded about it now by a 68K post …

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Blogs

Scrambling for time atm!

May 29, 2021 Retro Ports

Stars are still WIP, I’ve been coding the algorithm to produce the tile data and also the data for optimal palette cycling. However work has gotten very busy (plus the Giro d’Italia is currently running) so I haven’t done a lot lately. Work will still be busy for another work …

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Blogs

A star is… coded.

May 19, 2021 Retro Ports

┬áSo I have a plan for the stars. There are 124 stars, and using 16×16 tiles would require 103 tiles to contain them. Tiles have no more than 3 stars in them. Tiles will also have their own palette (16 colour entries). There are 4 blink cycles. Rather than use …