R4600

The R4600, code-named "Orion", is a microprocessor developed by Quantum Effect Design (QED) that implemented the MIPS III instruction set architecture (ISA). As QED was a design firm that did not fabricate or sell their designs, the R4600 was first licensed to Integrated Device Technology (IDT), and later to Toshiba and then NKK. These companies fabricated the microprocessor and marketed it. The R4600 was designed as a low-end workstation or high-end embedded microprocessor. Users included Silicon Graphics, Inc. (SGI) for their Indy workstation and DeskStation Technology for their Windows NT workstations. The R4600 was instrumental in making the Indy successful by providing good integer performance at a competitive price. In embedded systems, prominent users included Cisco Systems in their network routers and Canon in their printers.

IDT was the first company to fabricate and ship the R4600. IDT produced first silicon in August 1993. The first part was a 100 MHz part announced in October 1993. In March 1994 at CeBIT, IDT announced a 133 MHz part. Both were fabricated in a 0.65 μm CMOS process and required a 5 V power supply. NKK announced their version of the R4600, the NR4600, in the middle of 1994. The first NR4600 was a 100 MHz part fabricated in a 0.5 μm process that used a 3.3 V power supply.

The R4600 was a simple design; it was a scalar processor, issuing up to one instruction per cycle to its integer pipeline or floating-point unit (FPU). Most integer instructions have a single cycle latency and throughput, except for multiplies and divides. Multiplies, 32-bit and 64-bit, have an eight-cycle latency and six-cycle throughput. Divides have a 32-cycle latency and throughput for 32-bit integers and a 61-cycle latency and throughput for 64-bit integers.

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