Pregnancy testing has evolved into a digital version, turning into tiny computers that are almost as powerful as the original IBM PCs. Twitter users foone and xtoff recently disassembled a digital test pregnancy device sold by Wal-Mart. It costs less than $5 and includes a processor, memory, a button battery and a small LCD screen to display the results. The processor is an 8-bit Holtek microcontroller with 64 bytes of memory that can run at 4MHz or 8MHz, depending on the configuration of the battery. This may sound very basic, but the complexity of the chip is surprising.
You might think it’s very limited because it has only 64 bytes of memory, but it actually uses a pipeline architecture that runs at 1 instruction per cycle, which is pretty good for a 4MHz CPU. Foone speculates that the device may be faster in digital computing and basic I/O than the CPU used in the original IBM PC. IBM’s original PC was based on Intel’s 8088 microprocessor, an 8-bit chip operating at 5MHz. The difference here is that this is a digital pregnancy test stick that you throw away after a urine test.
This digital test has added an LCD screen and processor to digitize the pregnancy test, but the digital test still includes a note that reacts with urine. The note inside is like a wick, so when it’s wet, it activates the battery and supplies power to the device. The device then uses three LED lights and two photosensitors to read the lines on the note, which usually provide pregnancy test results. Processors, RAM, batteries, and LCD displays are literally designed to read notes and improve the clarity of the test by displaying “pregnant” or “not pregnant” on the display. Unfortunately, the chips inside are not programmable, so there is no viable way for Doom to run on these digital pregnancy tests.