macsehw/hardware/fpga/rtc/README.md

RTC Apple Custom Silicon

The RTC (Real-Time Clock) chip within the Macintosh SE is an Apple custom silicon chip that implements the real-time clock and battery-backed PRAM (Parameter RAM). Fortunately, its simplicity has yielded a fairly complete replacement chip design that is based around the pin-compatible ATTiny85 chip running appropriate firmware. See the firmware directory for details.

Nevertheless, if we do get a microscopic chip scan of the original silicon, this directory would contain corresponding design files to replicate the original design as-is. Since the chip design is so simple, this might be easily doable with conventional DSLR macro photography after the packaging is opened up.