The Archimedes was the first RISC home computer. There were three series, the 300, 400 and 500 which shared the same hardware basis: the ARM-2 processor (ARM-3 for the A500) and three custom chips dedicated to memory (MEMC), video (VIDC) and I/O (IOC) controls.
The 300 series had 512 KB to 1 MB of memory and two expansion slots (64 pin). The 400 series had 1 to 4 MB of memory and four slots (three 64 pin and one 96 pin). The 500 series had 16 MB of RAM.
The operating system, first named Arthur then subsequently RiscOS, was in ROM along with the WIMP graphic interface (Windows Menu Icon Pointer), the fast BBC Basic V interpreter and various utility programs, among them a Paint package, a music editor and an Acorn BBC model 2 emulator.
The built-in 800 KB 3.5" floppy drive was compatible with the old 640 KB format. A lot of expansion cards were developed for the Archimedes : MIDI, SCSI, Oscilloscope, IEEE 488, speech recognition, scanner, floating point co-processor.
Many programming languages were released as well : Basic (which could be loaded from disk and ran faster than the ROM basic), C, Fortran 77, Pascal, Prolog and Lisp.
Although it was at least two times faster than the Atari ST and Amiga models, the Archimedes had no real success because of its high price, except in its country of origin (Great Britain) where it was very well-known and commonly used (especially in schools).
These computers were followed by a great family of computers called RISC PC which are still in production.