This one was very similar to the 6128 except that the disk drive is a 5 1/4" one !! No more cursed 3" disks that were so hard to find in 85 because nobody else was using them.
The keyboard was exactly the same as the 6128. But if you look at the connections you can see MIDI plugs and a RS232 connector ! Alan Sugar tries to implement some real standards at last... Clearly, Amstrad wanted to prepare for the 16/32 bit battle, declared with the soon-to-be-launched Atari 520ST, but with an old Z80!! A lost cause from the start...
The RAM is not really 512k, but rather like its brother the 6128, there were several banks used as virtual RAM disks : 5 banks of 94 k each + the initial 42 k .
There were new BASIC instructions: CIRCLE, PAINT, SCROLL, CLOCK, MUSIC, etc. and many others to control communication with the RS232 connector.
The 5512 had its own internal clock that would keep time even after the computer was switched off. Wow!
But most impressive was the GUI. Yes, there was a real Graphical User Interface like Windows !! But it was slow, the Z80 could not perform miracles.
Of course it was fully compatible with the other CPCs.
OK, IT'S A JOKE ! Hebdogiciel (a very well known French newspaper/magazine in the 80's) made this joke on the first page of N°138 in June 85. AMSTRAD took them to court asking for 100 million francs in damages, arguing that this joke stopped the sales of the 6128 for one week, which may have been true...