The final addition to Acorn's Archimedes family of personal computers, released in April 1994. The RiscPC allowed a second processor, e.g. an Intel 486 or a second ARM, to share the bus, memory and peripherals with the main processor. It also had full 24-bit colour graphics support. The Risc PC 600 (the first to be launched) had the new ARM600 processor and RISC OS 3.5. The RiscPC 700 had an ARM710 processor and RISC OS 3.6, and the SA had the StrongARM processor and RISC OS 3.7. Castle Technology Ltd later introduced the IYONIX pc with the 32-bit X-Scale processor and USB sockets. USB and StrongArm can also be retrofitted to earlier RiscPCs. RiscPCs are among the most energy efficient home computers.