#risc

IBM’s Frank King appeared on an October 1986 “Computer Chronicles” to demonstrate the IBM RT PC, a $10,000 RISC-based desktop computer with 4 MB of RAM, a 70 MB hard drive, and IBM’s proprietary UNIX, AIX, featuring the X Window System. https://www.computerchronicles.blog/computer-chronicles-revisited-065-ibm-rt-pc/ #retrocomputing #risc

I'm investigating the original Berkeley RISC-I CPU out of historical interest and wonder why some instructions use more than one opcode (e.g. LDHI uses 16 opcodes 0x70...0x7F). I can't see why this is necessary – is this an optimization or am I missing something here? Details seems to be provided in Corcoran, G.T., "Using ISPS to Specify the RISC I Architecture and Implementation," Master's Report, UCB (Dec. 1980), but I can't find this online. #risc #berkeley #ucb #comparch #processor