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 The '''Spectrum''' and '''Commodore''' versions seem to have been actually released, but - as far as known - the Amstrad version wasn't ever 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.
== Info Fragments on Spectrum CD Games Pack (Code Masters) (1989) Pictures ==
The pack consists of a Audio CD with about 30 spectrum games (each one recorded twice), and a connection cable (cd player's 3<gallery>File:TheCdGamesPackForSpectrum128.5mm (or 6.3mm via adapter) stereo headphone socket to spectrum 9pin DSUB joystick port) (for jpg|Spectrum 128versionFile:CodemastersCDforC64.jpg|Commodore 64 versionFile:NoPicture.gif|Amstrad CPC versionFile:Inside the adapter.jpg|Inside of plug/+2cableFile:OliverTwinsCodemastersCD.gif|Info from http:/+3 or 48K with Kempston or sinclair joystick interface), and loading software on tape, once when a game is loaded one can press Q,U,I,T on keyboard to load a new game (without needing to load tape loader again)/www.olivertwins.com/File:CodemastersCdOriginalCable.jpg|Cable Connectors</gallery>
The loader asked the user to choose to use kempston or sinclair joystick interface.== ACU writes about Codemasters CD ==
A dissassembly <gallery>File:Codemasters CD Gamespack p1.jpg|ACU of the loader reveals the followingMarch 1990 - page 20File:Codemasters CD Gamespack p2.jpg|ACU of March 1990 - page 21File:Codemasters CD Gamespack p3.jpg|ACU of March 1990 - page 22</gallery>
For kempston:
Bit 4 (joystick fire) of port &1f is data.== Schematic ==
For sinclairJosé Leandro Novellón did some reverse engineering on the Spectrum cable in 2008. The results were released on http://www.speccy.org/trastero/cosas/JL/CableCD/CableCD.html (spanish). According that results, the cable is '''assumed''' to contain hardware like this: | C---------- Joystick.Pin1 (Up) |/ Audio Left (Tip) ------o----[330]----B| BC549B | |\ [1K] | E--+ | | Audio Gnd (Base) ------o----[470]----------o------- Joystick Pin8 (Common) | | [1K] | E--+ | |/ Audio Right (Mid)------o----[330]----B| BC549B |\ | 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 that multimeter tests can't reveal any additional small capacitors).
Bit 1 (joystick right/key '2') The material of port &f7fe the connector is datastill 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 you like to combine research with some minor destruction!'''
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.== Audio Signals ==
The cable is most likely to be monoBelow screenshots are showing some interesting sections of the Tracks on a Codemasters CD (screenshots are based on WAV files, because only 1-bit is used for loadingrecorded from the Spectrum version).
No info if/how * Theoretically the stereo signal audio signals should contain perfect '''rectangular waveforms''' - the tested WAV files did contain some '''analog dirt''' (the source of that dirt is usedunknown, either the original CD was mastered using analog equipment, or the CD-to-WAV conversion was done using analog sound input - or both). The cable does reportedly * As seen on the screenshots, the '''stereo signals''' contain a 1bit A/D converterthe same data on both left and right channel, which is probably a single transistor or so (so it's effectively a mono, not stereo?). The CD capacity is said to be "12 Megs" signal (presumably meaning 12 Megabit = 60 tracks with 25Kbytes eachwithout a clock signal or second data bit on one of the channels).
It is more probable that the Amstrad loader is similar to the Spectrum loader:<gallery>1. The CPC has same CPU as the File:SpectrumCodemasters CD Test Signal (Closeup).png|Track 1 - Test Signal (Closeup)2File:Spectrum Codemasters CD Low Speed Block. The CPC already has a number of loaders based directly on the png|Low Speed BlockFile:Spectrum ROM loader, so a conversion of this loader to CPC would be easyCodemasters CD High Speed Block.png|High Speed Block</gallery>
== Links ==* Track 1 contains a repeated '''Test Signal''' consisting of two long and two short pulses, intended to be used with the volume calibration function in the cassette loader. The length of the test signal is about 110 seconds, and it's a 'raw' waveform without preceeding header or pilot pulses.* Track 2-33 contain 32 spectrum games (average length 45 seconds each). Track 34 contains a slide show demo (about 390 seconds). Track 35-66 contain backup-copies of Track 2-33.* For whatever reason, the first block on each Track (except Track 1) is '''Low Speed Block''', using about the same pilot/sync/data pulse timings as normal Spectrum Cassette files. However, it is NOT a cassette file (which would consists of TWO such blocks, and which would contain other header/filetype values), the low speed block is around 6 seconds in length.* All further block(s) on each track are '''High Speed Blocks''', pilot/data pulses are shorter as on cassette blocks, the two sync files are longer as on cassettes.
* http://www.kjthacker.f2s.com/docs/audiocd2.html - DIY - '''caution:''' the disclaimer == Info Fragments on that webpage says that it is '''not''' based on the real Codemasters CD - so it may be totally incompatible to the original Codemasters Spectrum CD - also, Kevin has confirmed that it's an '''untested''' and '''unfinished''' DIY projectGames Pack (Code Masters) (1989) ==
* http://worldofspectrum.org/ - has The pack consists of a review about the Spectrum version - which conflicts Audio CD with the DIY info about 30 spectrum games (the Spectrum review implies it contains a mono 1-bit A/D convertereach one recorded twice), not and a stereo connection without A/D convertercable (cd player's 3.5mm (or 6.3mm via adapter) stereo headphone socket to spectrum 9pin DSUB joystick port) (the Afor Spectrum 128/D converter - if it does exist - might refer to something simple+2/+3 or 48K with Kempston or sinclair joystick interface), like and loading software on tape, to start loading or after a transistorgame is loaded one can press Q,U,I,T on keyboard to load (without needing to load tape loader again).
* http://www.olivertwins.com/ - according to this webpage, the Oliver Twins created "The loader has instructions and calibration so you can adjust the volume from the CD Games Pack" in December 1989, for Amstrad CPC, Spectrum, optimal and Commodore 64, published by Codemasterserror-free loading.
Whether or not The loader asked the Amstrad CPC version was actually released is a bit unclearuser to choose to use kempston or sinclair joystick interface. Did anybody ever see it for real?
== Pictures ==A dissassembly of the Spectrum loader reveals the following:
<gallery>File* For kempston:TheCdGamesPackForSpectrum128Bit 4 (joystick fire) (pin6 on a atari-style kempston port) of port &1f is data.jpg|Spectrum 128 versionFile* For sinclair:CodemastersCDforC64Bit 1 (joystick right/key '2') (pin6 on amstrad's non-atari-style spectrum +2 joystick port) of port &f7fe is data.jpg|Commodore 64 The loader is patched according to the interface chosen and appears to be a modified versionof the normal cassette loading functions in the Spectrum BIOS.FileIt seems to load the standard tape data structure:NoPicturepilot, sync byte, data bytes and checksum byte.gif|The loader uses only 1 bit (mono). The CD capacity is said to be "12 Megs" (presumably meaning 12 Megabit = 60 tracks with 25Kbytes each). It is quite probable that the Amstrad loader is similar to the Spectrum loader:1. The CPC versionhas same CPU as the SpectrumFile:NoPicture2.gif|Inside The CPC already has a number of plug/cableloaders based directly on the Spectrum ROM loader, so a conversion of this loader to CPC would be easy.File== Links == * https:OliverTwinsCodemastersCD//worldofspectrum.gif|Info from httporg/ - has a review about the Spectrum version * https://www.olivertwins.com/</gallery>- 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
* https://www.speccy.org/trastero/cosas/JL/CableCD/CableCD.html Rev-engineering the wire of the CD Games Pack for Spectrum.
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