CDC STAR-100
CDC STAR-100: a pioneering but mixed success in vector computing
- The CDC STAR-100 was a vector supercomputer made by Control Data Corporation and released in 1974. It was one of the first machines to use a vector processor and the first to use integrated circuits, offering about a million words of memory.
- STAR stands for Strings and Arrays, reflecting its focus on processing large blocks of data with vector operations. It aimed for a peak speed of 100 MFLOPS, faster than its predecessor, the CDC 7600.
- Hardware at a glance: the machine used a 64-bit CPU around 25 MHz and could have up to 8 MB of memory. Main memory stored 65,536 512-bit words in core memory and was accessed through wide 512-bit buses with a streaming unit to manage memory and instructions.
- The STAR-100 featured two arithmetic pipelines. One handled floating-point add and multiply, and the other handled scalar instructions. It also had a floating-point add, multiply, and divide unit. The pipelines could be split into four 32-bit lanes to boost throughput to 100 MFLOPS, but this reduced precision.
- Vector processing was a core idea: the machine used 65 vector instructions and 195 total instructions. Vector operands lived in consecutive memory locations, and operations worked on large blocks of data stored as 512-bit “superwords.”
- I/O was handled by separate 16-bit I/O processors, each with its own memory. These I/O processors shared a wide 128-bit data bus to the memory system and helped offload tasks from the main CPU.
- Real-world performance did not live up to theoretical potential. Vector instructions had long startup times and the machine’s clock was slower than competing designs, so many programs saw limited gains unless they were highly vectorizable. Scalar performance could also drag down overall speed.
- Only three STAR-100 systems were ever delivered: two to Lawrence Livermore National Laboratory and one to NASA Langley Research Center. To help developers, LLNL created STACKLIB, a library on the older 7600 to emulate STAR’s vector capabilities and improve performance.
- The STAR-100’s disappointing performance and high costs contributed to CDC losing ground in the supercomputer market, especially with the Cray-1 entering the scene in 1975. Jim Thornton, the STAR’s chief designer, left CDC to found Network Systems Corporation.
- A later lineage built on the STAR’s ideas emerged as the Cyber series (Cyber 203 in 1979 and Cyber 205 in 1980), but by then faster systems from Cray and others had changed the competitive landscape. Five STAR-100 machines were built in total, with deliveries starting in 1974.
This page was last edited on 3 February 2026, at 09:42 (CET).