Ken posted an article taking a closer look at AMD’s Am2901 chip:
You’re probably familiar with modern processors made by Advanced Micro Devices. But AMD’s processors go back to 1975, when AMD introduced the Am2901. This chip was a type of processor called a bit-slice processor: each chip processed just 4 bits, but multiple chips were combined to produce a larger word size. This approach was used in the 1970s and 1980s to create a 16-bit, 36-bit, or 64-bit processor (for example), when the whole processor couldn’t fit on a single fast chip.
See the full details on Ken Shirriff’s blog.