Direct Disk to Cartridge Port
The practise of some GX4000 cartridge game developers was to put an almost unchanged game from the CPC into a cartridge for the Plus/GX4000.
Contents
Disk Vs Cartridge
Sometimes such games had some features removed because the 128KB only cartridge had less capacity compared to a 3" disk (178K with standard DATA format with later disc games used around 210K on each disc, compared to 128KB used for most cartridge games) and in addition there was no way to store game state (i.e. the cartridge contained an EPROM and the ACID protection chip only, no EEPROM or RAM). It is worth noting that 256KB and 512KB (max capacity) can be used with cartridges but most used 128KB ROMs.
Consequences
Of course this practise didn't help the Plus range at all and was almost as shameful as the Speccy Port technique.
It was a cheap and fast way to quickly release games.
Another problem came from the fact that both the 464Plus and GX4000 (essentially a cut down 464Plus) had 64KB ram. As a result using the Plus features to the full was not so simple if the game was to run on these systems. If 128KB ram was the minimum then this would have allowed more flexibility for graphical data, sampled sound etc and would have easily enhanced a 64KB only game.
A 6128PLUS config with 512K ROM cartridge and disk Drive support is the optimum PLUS config, but such beast was never fully unleashed yet.
Almost Direct Disk to Cartridge Port
Most games with CPC and PLUS versions are "Almost Direct Disk to Cartridge Port", a "Direct Disk to Cartridge Port" with small modifications. The use of the extra Plus features varied a lot. Some didn't use much, others used more.
Examples of Direct Disk to Cartridge Ports
These could have benefited from using the Plus 4096 colour palette as a minimum.
Examples of Almost Direct Disk to Cartridge Ports
Some other cartridge games looked similar to the CPC version, but did have some enhancements. Some examples:
This was better than the direct ports.
Price comparison
Thankfully most of those games were known as good games on the CPC. The bet was that it would still be a good game on Plus.
Yet people were not interested in buying an expensive cartridge with no or few advantages when the CPC version could be bought for cheaper and played on the Plus.
UK prices: in 1990 when the Plus/GX4000 was released, cartridge games were sold at £29.95, while disc versions were normally £14.99 and tape version was £9.99. Blank discs were £2.50 each. (Source Amstrad Action October 1990)
French prices: in 1990 when the Plus/GX4000 was released, cartridge games were sold for 250Fr , 150Fr for disc and 100Fr for tape. Blank discs were 20Fr each. (Fr = French Francs, pre-Euro currency in France).
The present and future
It is nowadays a common feature to modify existing CPC games into "Almost Direct Disk to Cartridge Port", just by modifying the colours in game to use a better choice of colours from the Pluss bigger palette.
As most cartridges were the original games released from the GX4000 era, it was mostly applied to games. Now that the operation of the ACID protection chip is known, and the development of various homebrew cartridge hardware solutions may lead to Direct Disk to Cartridge Port applied to any kind of software or new cartridge games that make fuller use of Plus features.
