Laurens Holst wrote:
>
> Hmmm, this all sounds very encouraging.
>
> Maybe I should just lay a wire from the clockchip to the PSG and the
> slotexpander pin???
>
> By the way, I don't think external RAM uses the sync signal, does it?
older memorymappers (like those from Checkmark, ...) rely on the 3.58MHz
clock signal for DRAM access. These don't work with a clock of 7MHz.
(you can recognize these by looking at the chips on the board: if you
see a chip with two times the number 74 on it; like 74LS74)
'modern' memorymappers don't rely on the clocksignal. So these will work
ok at 7MHz busspeed.
> Otherwise it wouldn't work on an MSX-turboR either, because that one has
> 3.58 MHz on the pin in the slot too.
yes.. but busspeed on the cartridgeslots *IS* only 3.58MHz. All memory
reads and writes to the cartridgeslots are @3.58MHz. That's why a
Turbo-R is rather slow when programs are executing in an external
mapper... (but it is still faster than a normal MSX2 because R800 cpu
core is faster when executing the instructions.)
So all you have to do to obtain good sound @7MHz:
- replace the clockconnection to your cartridgeslot with the (old) fixed
3.58MHz signal (can be found somewhere in the computer)
- don't use old memorymappers
- MSX-Audio will work ok (except sometimes wrong notes,... because of
too fast I/O; but this can probably be solved by rewriting the
replayercode)
- SCC will always work ok
- MSX-Music: I don't know: probably the same as the MSX-Audio; BUT it
can be possible that for the MSX-Music, the clock has to be synchronized
with the busspeedsignals (read/write which happens @7MHz) (for MSX-Audio
this is not necessary)
- PSG: big problem I think: it is integrated in the msxengine; does that
have a separate clockinput for the PSG sound generation??
Greetings,
Jon
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