Decoding the NEC V20 Microcode
owl writes:
https://martypc.blogspot.com/2026/09/decoding-nec-v20-microcode.html
reenigne's decoding of the 8088 microcode in 2020 opened the doors for extremely accurate emulation of the 8088 CPU.
Although I had added support for the NEC V20 in MartyPC, the V20 core was not cycle-accurate in terms of the V20's actual timings. It was an 8088 in a V20's clothing - a copy-paste of my 8088 core with V20 instructions tacked on.
This was not an ideal case, but the prospect of making my V20 core cycle-exact without the microcode seemed like it might be a discouraging slog of trial and error.
So why not get the microcode, then?
I recently commissioned InfoSecDJ to take die photography of an NEC V20 CPU (actually a second-source V20 fabricated by Sharp, but a V20 nonetheless). He did an excellent job.
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