F‑14 CADC on Spartan‑7

Aircraft air data computers turn pressure and temperature into speed, altitude, and wing commands. One engineer has now rebuilt the F-14A Tomcat’s version inside a Spartan-7 field-programmable gate array, or reconfigurable chip. (github.com) The project repository says the original F-14A Central Air Data Computer took inputs including static pressure, impact pressure, total air temperature, and angle of attack, then produced Mach number, altitude, airspeed, vertical speed, wing sweep commands, and flap positions. The new build implements that logic in VHDL, a hardware-description language used to define digital circuits. (github.com) The engineer’s posted implementation figures put the design at about 2,000 look-up tables, 1,100 flip-flops, and one digital signal processing slice on a Spartan-7. AMD’s 7-series documentation describes look-up tables and flip-flops as the basic building blocks inside that chip family. (x.com) (digikey.com) The original computer was built for the F-14 between 1968 and 1970 by Garrett AiResearch, with Ray Holt among the engineers tied to the design. The GitHub documentation says it used 20-bit fixed-point math, a 1.5 megahertz master clock, and roughly 54.6 milliseconds per update frame. (github.com) That matters because the F-14 computer sits in a long-running argument over what counts as the first microprocessor. The repository describes it as “arguably the world’s first microprocessor,” while other accounts note the claim depends on whether a multi-chip processor counts the same way as a single-chip commercial product like Intel’s 4004. (github.com) (hackaday.com) The F-14 system was not a single modern chip. Wikipedia’s summary of the historical design says the MP944 chipset ran at 375 kilohertz inside a 28-chip system using 74,442 transistors and six unique chip types, including multiplier, divider, steering-logic, and storage units. (wikipedia.org) The new reconstruction maps those old functions onto programmable logic, where a field-programmable gate array acts like blank hardware that can be rewired with code. The repository lists separate modules for the multiplier, divider, steering logic, register storage, control sequencer, and an input-output bridge. (github.com) The posted demo also links the FPGA to a Raspberry Pi Compute Module 5 for live sensor inputs and wing-position visualization. Raspberry Pi says Compute Module 5 is the embedded version of Raspberry Pi 5 hardware, built around a 64-bit Arm processor running at 2.4 gigahertz. (x.com) (raspberrypi.com) The result is less a nostalgia project than a hardware translation: a flight computer designed around late-1960s constraints now runs on a small modern fabric board with its source code published. The repository includes original documents, verification files, and synthesizable hardware modules for anyone who wants to inspect or extend it. (github.com)