Digital pregnancy tests are almost as powerful as the original IBM PC

Pregnancy tests used to be fairly simple sticks you peed on, but the move to digital versions has transformed them into tiny computers almost as powerful as the original IBM PC. Fascinated by the digital era of pregnancy tests, Twitter users foone and xtoff recently pulled apart examples from Walmart and Clearblue to reveal what’s really going on inside.

Each test, which costs less than $5, includes a processor, RAM, a button cell battery, and a tiny LCD screen to display the result. The processor is an 8-bit Holtek microcontroller with 64 bytes of RAM, capable of running at either 4Mhz or 8Mhz depending on the battery configuration. That might sound very basic, but the chip is surprisingly complicated.

“You might think it’s very...

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