The Codemasters CD was a compilation of games from Codemasters which came on a Audio CD, bundled with a special connection cable to connect an Audio CD Player to the Joystick Port. Since the computer can't boot from the Joystick Port, it also included boot software on cassette. The Codemasters CD was announced for ZX Spectrum, Commodore C64, and Amstrad CPC.
However, only the '''Spectrum''' and '''Commodore''' versions seem to have been actually released. According to the Oliver Twins (the makers of the CD), the '''Amstrad CPC''' hardware did exist, too. Though this seems to have been only an unreleased prototype.
== Schematic ==
| C---------- Joystick.Pin6 (Fire)
The above circuit was rev-engineered by measuring the resistance between the cable pins, but without opening (=destroying) the moulded plastic connector that houses the original circuit - so far, it isn't fully confirmed if the original cable does really contain the above components (not to mention multimeter tests can't reveal any additional small capacitors).
The material of the connector is still unknown, but if it's soft/elastic then it should be extremly easy to peal off the plastic with a knife and pincers, for revealing what is really in there.
'''You are welcome to add your own results here if like to combine research with some minor destruction!'''
== Audio Signals ==
A dissassembly of the loader reveals the following:
4 (joystick fire) of port & 1f is data.
Bit 1 ( joystick right/key '2') of port &f7fe is data.
The loader is patched according to the interface chosen and appears to be a modified Spectrum ROM loader. It seems to load the standard tape data structure: pilot, sync byte, data bytes and checksum byte. The cable is most likely to be mono, because only 1-bit is used for loading. No info if/how the stereo signal is used. The cable does reportedly contain a 1bit A/D converter, which is probably a single transistor or so (so it's mono, not stereo?). The CD capacity is said to be "12 Megs" (presumably meaning 12 Megabit = 60 tracks with 25Kbytes each). It is more probable that the Amstrad loader is similar to the Spectrum loader:
1. The CPC has same CPU as the Spectrum
2. The CPC already has a number of loaders based directly on the Spectrum ROM loader, so a conversion of this loader to CPC would be easy.
== Links ==
* http://www.kjthacker.f2s.com/docs/audiocd2.html - DIY - '''caution:''' the disclaimer on that webpage says that it is '''not''' based on the real Codemasters CD - so it may be totally incompatible to the original Codemasters CD - also, Kevin has confirmed that it's an '''untested''' and '''unfinished''' DIY project * http://worldofspectrum.org/ - has a review about the Spectrum version - which conflicts with the DIY info (the Spectrum review implies it contains a mono 1-bit A/D converter, not a stereo connection without A/D converter) (the A/D converter - if it does exist - might refer to something simple, like a transistor)
* http://www.olivertwins.com/ - according to this webpage, the Oliver Twins created "The CD Games Pack" in December 1989, for Amstrad CPC, Spectrum, and Commodore 64, published by Codemasters
Testing the wire of the CD Games Pack for Spectrum. Whether or not the Amstrad CPC version was actually released is a bit unclear. Did anybody ever see it for real? == Pictures == <gallery> File:TheCdGamesPackForSpectrum128.jpg|Spectrum 128 version File:CodemastersCDforC64.jpg|Commodore 64 version File:NoPicture.gif|Amstrad CPC version File:NoPicture.gif|Inside of plug/cable File:OliverTwinsCodemastersCD.gif|Info from http://www.olivertwins.com/ File:CodemastersCdOriginalCable.jpg|Cable Connectors </gallery>