Back in November and December of 2020 there was some discussion around measured non-linear ramps in Sega Master System’s blue channel. A tweet exchange between Chris Covell and Bernard Bygott lead to some interesting measurements and documentation written by Bernard with the assistance of Tianfeng and others, which we covered in January:
Just this week, hardware reverse engineering expert Furrtek went several steps further, decapped a Sega Master System VDP (a YM2602 from a Sega Master System 1 console), and took some high resolution photos. The process revealed a very blatant difference in the Blue line compared to Red and Green, which confirms the earlier observations.
Furrtek shared the discoveries on the SMS Power! forums:
As well as announcing them on Twitter:
Sega Master System I VDP aka YM2602, the recently discovered least significant bit offset on the blue channel is intended ! pic.twitter.com/z6aZyXewGM
— Furrtek (@furrtek) March 8, 2021
As always, a fantastic result by a collective of generous and sharing individuals all striving for improved accuracy and documentation of these old systems. All of this work has fantastic on-flow effects into emulators, FPGA simulations and repairs for the entire retro-gaming community.