Amstrad acquired Sinclair at some point fairly late in the game, and the PC-1512 and the higher end PC-1640 were the first Amstrad Branded PC’s that left the stables, following Sinclair’s initial attempt with the PC-200.
The Principal difference between the two models was the RAM, with the 1512 having only 512k, and the 1640 having .. wait for it… 640k.
Both PC’s had choices of Single 5.25″ Drive, Dual 5.25″ Drive, or Single 5.25″ Drive plus Hard Drive models.
One friend had a Dual Drives model 1512 which was quite handy as he could leave the DOS Boot Disk in A: while using B: for applications. I remember evenings with both of us trying to play a DOS based version of Core Wars, and he writitng programs to calculate the value of PI to a ridiculous number of decimal places, just for the hell of it!
Graphics were provided with a choice of Hercules Mono or CGA Graphics on the 1512.
Both models came provided with the GEM/3 Desktop environment and a few simple apps.