The CPC [[Printer Port]] has only 7bit data. Which is okay for english 7bit ASCII character sets, but not enough for 8bit character sets. Also, printing bitmap graphics usually requires 8bit data (though usually can also print 7 pixels columns combined with a reduced line-feed rate). Amstrad's DMP1 works perfectly with 7bit, but Amstrad's later DMP2000/DMP2160 include a few functions that won't work on 7bit ports- so even the official CPC printers aren't fully compatible with the CPC printer port.
== Internal 8bit Printer Ports/Mods ==