Computer history: Control Data 6400 system


Control Data 6400

The Control Data 6400 system was a less-powerful variant of the famous Control Data 6600, which was introduced in 1964. The 6600 is sometimes referred to as the first Reduced Instruction Set Computer (RISC), due to its limited instruction set and generally uncomplicated design. Under the covers, the CPU was a traditional unified processor, as opposed to the more sophisticated 6600 with its multiple functional units (see its configurator at Like the RISC machines of the mid ninetieth, the 6600 could execute multiple instructions simultaneously using an advanced architectural design. The Control Data 6400 lacked that capability, making it a 2.5 times slower machine than the single-CPU 6600. 

By the mid-’70s, Control Data, a member of the original BUNCH competitors to IBM (Burroughs, Univac, NCR, Control Data, and Honeywell) had a less-than-robust share of the computer market. It may be surprising, then, that it supported several operating systems on its 6000 series. These included:

  • KRONOS, a by then seldom-used interactive-oriented OS.
  • SCOPE 3.4. the vendor support for SCOPE was fading by the mid-’70s.
  • NOS/BE, a follow-on to SCOPE 3.4, which integrated interactive computing better than SCOPE 3.4 did. NOS/BE stood for Network Operating System/Batch Environment.
  • NOS, a follow-on to KRONOS that added better batch support and networking. In fact, NOS stood for Network Operating System, a definite misuse of the phrase.

Back then, our idea of an “application” was a compiler or OS utility; there weren’t too many commercially available traditional applications for CDC systems. However, there were SPSS (a statistical package) and IMSL (FORTRAN math subroutine library).

Control Data over time developed four lines of computers compatible with the original 6600: the 6000 Series, the Cyber 70 Series, the Cyber 170 Series, and the Cyber 180 Series series. (the 7600 and its successors are included in with these four lines, even though the 7600 had slightly different I/O.) There wasn’t a whole lot of difference amongst the 6000 (discrete technology; core memory), 70, and 170 lines with the exception of the type of packaging, memory and cooling technology. On the other hand, for the most part, the Cyber 180 Series really was a new line. Most of the Cyber 180s were dramatically different Complex Instruction Set Computers (CISC) that had a 6000 compatibility mode. (There were a few models in the 180 Series that were just of the same old architecture with a new name.)

The Control Data 6400 had roughly the power of an Intel 386+387 and a MIPS performance which could probably be bought in 1995 on the second-hand market for about US$ 400.

One of the 12 boards of a memory block showing 64*64 bits.
One of the 12 boards of a memory block which contains 64*64 bits.