Amstrad released the CPC 664 in june 1985 (knowing that the CPC 6128 would follow very soon). It is based upon the 464 hardware but with a built-in 3” disc drive interface instead of the tape deck. Besides, a revised version (40008) of the Gate Array appeared, the first Gate Array version (40007) used in the 464 was not very reliable. It was possible to purchase a CPC 664 with a green screen (GT65) or color screen (CTM644). The built-in disc drive interface is the same than the Amstrad DDI-1 add-on for the 464.
Like the 464, it has it's OS and BASIC interpreter built-in as ROMs, but the Amstrad firmware got updated to version 2 and the Locomotive BASIC to v1.1.
The project codename was IDIOT: Includes Disc Instead Of Tape (don't take that too seriously, I'm not sure at all about it but I find it very funny :)
This is what a CPC 664 displays on startup (with a color monitor/tv set). The firmware indicate (v2) and the Locomotive BASIC say 1.1
The CPC 664 only had an english keyboard layout (no french/spanish/etc localisations were made).