On Fri, 18 Jan 2002, FRS wrote: > Hi Richard, > > Is the clock output of the SMS expansion port 3.57Mhz or 8Mhz? I ask this > because Sega overclocked the YM2413 to 8MHz on SMS. (The datasheet says it > should run at 3.57Mhz)
Interesting. What is your basis for this information? For Sega to run the YM2413 at 8MHz would be strange, since there is a perfectly good 3.58MHz clock available at the Master System (Mark III) expansion port. My design connects the Master System clock line directly to the MSX one, so it runs the YM2413 at 3.58MHz, or 3.54MHz in some PAL machines. (not all - I think) > If you are running the YM2413 at 3.57Mhz probably all notes will sound at > higher frequency than they should. You should compare both Aleste1 > versions (SMS and MSX2) to test if you're running at the right clock. At > 8Mhz the musics will be equal, but at 3.57Mhz it will sound horrible. They would sound lower, if clocked at 3.58MHz when intended to run at 8MHz. More than an octave lower. Envelope times would also be longer and the LFOs would be slower. However, note that the tempo of the music itself would remain the same. > The MSXs drivers on MESS is suffering of this effect, because yhe > YM2413-okazaki is overclocked to 8MHz, probably to match the SMS driver... This may be a "feature" in MESS... Incidentally, there is a small mistake in my diagram; I noticed it last night. I'll correct it now and also make a simplified version of the diagram so you can see more clearly which connections are being made. Richard -- For info, see http://www.stack.nl/~wynke/MSX/listinfo.html
