Hi you all,
Laurens Holst <[EMAIL PROTECTED]> wrote:
>I was wondering... When my MSX works at 7MHz, the sound gets all garbled up.
>So now the rest of the motherboard (and the cartridges) get the 7MHz clock
>signal. Is it possible to 'block' this signal and relay the old clock signal
>(if the chrystal is still there?) to the rest of the motherboard???
>
>I don't think this can harm (turboR does the same, doesn't it? Only the
>processor needs the higher clock frequency), and it would be great to
>finally get rid of the sound-problems with for example PSG, SCC, FM-PAC,
>MSX-Audio (one of my MSX-Audio devices already has got its own chrystal).
This is possible, but depends on the following:
In MSX machines I know, the standard 3.58 MHz. clock signal is used for 2
purposes:
-CPU clock,
-and as base frequency for audio generating IC's.
The CPU clock signal is often used to control the signal timings of
DRAM memory in the machine. And here is the issue:
If these funtions are seperate (read: in seperate IC's), then you can simply
'feed' 3.58 MHz. to the audio parts, and the, possibly 7 MHz., CPU clock to
the Z80 and DRAM controlling IC('s?).
But if this is all controlled by one central IC ('MSX-engine'), then you can't
seperate these funtions. If you would feed it the old 3.58 MHz. signal, then
the DRAM timing would have no relation anymore with the CPU clock.
-> DRAM wouldn't work -> well, you get the idea...
This setup (one big IC) is used in MANY machines.
Exceptions are possible here as well:
You could add your own logic for generating the DRAM control signals, or
you could use SRAM instead....
In short: it all depends on your particular machine, and what you're willing
to change.
Greetings,
Alwin Henseler ([EMAIL PROTECTED])
http://huizen.dds.nl/~alwinh/msx MSX Tech Doc page
(not updated in a looonnng time, but several goodies are still there ;-))
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