The DF-224 is a space-qualified

computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...

used in space missions from the 1980s. It was built by Rockwell Autonetics. As with many spacecraft computers, the design is very redundant, since servicing in space is at best difficult and often impossible. The configuration had three CPUs, one active and two spares. The main memory consisted of six memory units, each with 8K 24-bit words of plated wire memory, with up to 48K words total. Four memory modules could be powered up at one time, resulting in a maximum of 32K words of available memory, though some applications such as the

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

used fewer memory banks to allow for graceful failure modes. There were three I/O processors, one operational and two backups. The power supply consisted of 6 independent power converters, with overlapping coverage of the operating functions. The processor used

fixed-point arithmetic In computing, fixed-point is a method of representing fractional (non-integer) numbers by storing a fixed number of digits of their fractional part. Dollar amounts, for example, are often stored with exactly two fractional digits, represen ...

with a

two's complement Two's complement is the most common method of representing signed (positive, negative, and zero) integers on computers, and more generally, fixed point binary values. Two's complement uses the binary digit with the ''greatest'' value as the ''s ...

format. Compared to computers that came later, the DF-224 was big and slow. It was roughly by by , weighed , and had a clock speed of 1.25 MHz. The DF-224 on HST was augmented with a 386 co-processor on the first servicing mission (SM1). This had a clock speed of 16 MHz. In Hubble servicing mission 3A the DF-224 (with co-processor) was replaced by the ''Advanced Computer'' using a 25 MHz Intel i486, and much more storage The DF-224 was one of the candidate computers for the Space Shuttle, but was not selected. It was also baselined in a version of a reusable Agena upper stage for use with the Shuttle, but this was never built.

References

{{reflist Avionics computers Radiation-hardened microprocessors Hubble Space Telescope

See also

References