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S-100 VDP MSX2 compatibility issue


I thought we couldn’t have MSX2 compatibility with the S-100 VDP since MSX2 requires a Yamaha YM2149 sound generator instead of a GI AY-3-8910.


Well it turns out by sheer luck that the AY-3-8910 and YM2149 are pin compatible except for pin 26.  Also if pin 26 has the option of being grounded then it enables new features of the YM2149. 


What’s amazing is the S-100 VDP already includes a jumper on AY-3-8910 pin 26 to ground option.  So I think we could just substitute a YM2149 for the AY-3-8910 and it *should* just work and with no other changes.


Maybe we could get MSX2 compatibility after all?  I hope so!

Thanks and have a nice day!

Andrew Lynch