「What is Game Boy?」にこのような記述があります。
The Game Boy has a custom SM83-based CPU, often called the SM83, which can be considered either as a stripped-down Z80, or a slightly upgraded 8080. It runs at a whopping 4MHz, though it can be simplified to a 1MHz, since, except in a few extremely edge-y cases, everything take a multiple of 4 cycles. Game Boy Color software can ask the console to double its CPU speed.
"SM83": Someone on the GBDev Discord server claims to have seen datasheets for other Sharp microcontrollers or systems on chip that have the same instruction set as the Game Boy CPU, and they call the core "SM83". I'd like to get the identity of this datasheet into a form that I can cite, as things said only in chat tend to disappear down a memory hole more quickly than things said in a newsgroup post, mailing list post, or other forum post with a URL.