The DF-224 is a space-qualified

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

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 Plated-wire memory is a variation of core memory developed by Bell Laboratories in 1957. Its primary advantage was that it could be machine-assembled, which potentially led to lower prices than the almost always hand-assembled core. Instead of t ...

, 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 (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

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, representi ...

with a

two's complement Two's complement is a mathematical operation to reversibly convert a positive binary number into a negative binary number with equivalent (but negative) value, using the binary digit with the greatest place value (the leftmost bit in big- endian ...

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 serving 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 The Intel 486, officially named i486 and also known as 80486, is a microprocessor. It is a higher-performance follow-up to the Intel 386. The i486 was introduced in 1989. It represents the fourth generation of binary compatible CPUs following th ...

, 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