Tokugawa Corporate Forums

I have a problem with the CD-ROM game "Emit - Vol.3" for PC-9821 in my "PC-9821 Cereb".
The graphics are out of sync with the voices. Graphics are slower than the voices, so when, for example, Yuko voice is playing, after that, I can see Yuko moving her mouth. That's very annoying.
I have "Emit - Vol.1" and that game doesn't have this out-of-sync problem, and I don't have this problem with any other game either.

I have tried with different combinations of CD-ROM drivers (NECCD.SYS, NECCDM.SYS, ...) and different versions of the AVGDRV.SYS but the problem is always exactly the same.
With GDC at 5 MHz instead of 2.5 Mhz the problem is the same too.

Any idea of what's happening?

By the way... Does have anyone a good dump of the original "boot disk/system disk" of the game? (not those modified for playing with NekoProject21 and other emulators). Thank you.