F-14A Central Air Data Computer (CADC) FPGA Reconstruction

A modern FPGA implementation of the F-14A Tomcat's Central Air Data Computer, originally designed by Ray Holt at Garrett AiResearch in 1968-1970. This was arguably the world's first microprocessor , predating the Intel 4004 by two years but remaining classified until 1998.

In 1968, the U.S. Navy commissioned Garrett AiResearch to develop a digital air data computer for the new F-14A Tomcat fighter. Engineer Ray Holt, just 23 years old, led the design of a revolutionary single-chip processor architecture that would compute critical flight parameters in real-time.

The system computed Mach number, altitude, airspeed, and commanded the F-14's distinctive variable-sweep wings based on flight conditions.

HDL Source ( hdl/ ) Complete synthesizable VHDL implementation of all six original CADC chips:

VHDL testbenches for each module with automated verification.

cadc_interactive.py — Interactive visualization tool with F-14 wing sweep display test_cadc_uart.py — Automated FPGA test suite via UART Polynomial verification notebooks FPGA Implementation ( implementation/ ) Vivado project for the Adiuvo Tile (Spartan-7 based SoM) with:

Simulation (ModelSim/Questa) cd sim run_cadc_top.bat # Run full system testbench run_pmu.bat # Test multiplier run_pdu.bat # Test divider Interactive Visualization cd verification python cadc_interactive.py # Simulation mode python cadc_interactive.py --live # Connected to FPGA The visualization displays:

Open implementation/vivado_proj_tile/ in Vivado 2024.1+.

Parameter Value Word Width 20 bits (Q1.19 fixed-point) Master Clock 1.5 MHz Frame Rate 18.3 Hz (54.6 ms/frame) Operations/Frame 512 Original Transistors 74,442 Original Power ≤10 watts Project Structure f14-CADC/ ├── hdl/ # Synthesizable VHDL source ├── tb/ # Testbenches ├── sim/ # Simulation scripts ├── specs/ # Design specifications (detailed docs) ├── verification/ # Python tools and notebooks ├── implementation/ # Vivado FPGA project ├── ocr_text/ # OCR'd original design notes └── original_docs/ # Ray Holt's original design PDFs References Ray Holt's original design documentation (included in original_docs/ ) The Holt Chip — Ray Holt's website F-14 Tomcat NATOPS Flight Manual License This reconstruction is provided for educational and historical preservation purposes.