Just completed the build for the game board. This board is based on the YM2149 audio chip - with integrated game controller ports.
Its ports are configured as per the MSX specification.
The AY-3-8910 chip could also have been used, but to keep thing simple, i just locked in the YM2149 chip. They apparently have subtle sound quality differences with the major differencing being the Ym2149 has an onboard clock divider.
The board also supports mixing in other external audio signals -- in anticipation for full MSX capability.
The demo below is with my port of Octo/chip8 games running on a stock rc2014 build.
(I have not tested it under the MSX configuration yet)
The Chip8/Octo port project is at: https://github.com/vipoo/rc2014-chip8 (It's not fully implementing all the octo instructions yet)
More details of Chip8/Octo can be found at: https://github.com/JohnEarnest/Octo
Game controller board project page: https://github.com/vipoo/rc2014-game (includes schematic)
And shoutout for the controller from: http://retrogameboyz.com