Reverse engineering a rare 1960s diode-transistor logic chip

[VoidRanger24]

An unidentified chip from a collection has turned out to be a rare piece of computing history. Hackaday reports that CuriousMarc found a Signetics ST680a quad NAND gate among his unknown ICs and decapped its plastic package with hot air

Ken Shirriff then analysed the die and published the results on his blog, righto.com. Plastic packages are harder to decap than ceramic ones, so getting a clean look at the die took care

Each gate sums its inputs using diodes, which then drive transistors. Hackaday describes the design as quite simple

The chip was one of the earliest integrated circuits in a plastic DIP package. Diode transistor logic was soon replaced by transistor transistor logic, led by Texas Instruments' 5400 and 7400 series

Looking inside early chips shows how far electronics has come in just a few decades. CuriousMarc and Ken Shirriff are a brilliant team for this kind of detective work. Preserving the details of forgotten logic families helps tell the full story of computing

Have you ever decapped a chip? And which piece of computing history would you love to see analysed next?

Reverse Engineering A 1960s Diode-Transistor Logic IChackaday.com