:The MSX standard requires "CPU clock, 3.58 MHz." on pin 42 (which
:would it be?). You might consider this 2 signals in one, usually the
:same. The idea discussed here, comes down to making this 2 separate
:signals, CPU clock, and 3.58 MHz.
:
:What's next, is to consider what should be on pin 42: CPU clock, or
:3.58 MHz.? You suggested the latter, and that could well be easier in
:practice.
There should be 3.58MHz on pin 42... The turboR also has got it...
Anyway, when everyone was really obeying to the standard, I think every chip
like the MSX-Audio would have to send a wait-signal to the CPU everytime
I/O-access was done, so that it will also work on future faster
MSX-computers. Or the faster computers should have something built-in like
on the turboR, that delays the processor (using WAIT) the prescribed time...
However, this is not easy (and cheap?) to make (you should use these
"programmable IC's")... And you'll need a list of all currently available
software, the I/O-ports they use and the waits they need...
However, if someone can construct something like this, then this can be used
in every 7MHz/Z380-'expansion'...
:> Not so negative! 'Reserved' signals are intended for future
:> expansion! Don't Fight the Future ;-)
:
:Yes! Great! Butteh...if you want to use/define these pins, then why
:not put on there:
:-A signal allowing the use of Direct Memory Access (for fast
:harddisk-interfaces etc.)
Ohhh... Ahhh... if that could be possible on MSX... DMA...
:-A signal allowing the INPUT of a RESET-signal (so that a cartridge
:might reset the computer, if for instance, it detects a 'dip' in the
:power supply)
Well just select subslot 0 of slot 0 and do a jump to #0000... not too
difficult.
:-A signal allowing a cartridge to generate non-maskable interrupts
Useful... Although that might cause problems when having disk-access... I
think it is not _nessacary_.
:-A signal that might be used to replace a ROM built in the computer,
:with one in the cartridge
:Just a few ideas (you can all come up with more like these)
:
:Using one of only 2 reserved pins for a CPU clock or 3.58 MHz.
:signal, sounds more a less like a 'waste' to me.
:> AFAIK the only cartridges that will need modification(one wire
:> changed) are the external memorymappers if you want to use them on a
:> modified MSX (or in other words on a 7MHz MSX)
:
:Not the Mega-mappers, by Digital KC, they don't use the clock signal
:(see schematic in MSX Computer Magazine 65).
:Just some other cartridges that MIGHT give trouble:
:-modems/RS-232/MIDI-interfaces, if they use 3.58 MHz. to generate
:baud-rates
The MT-Telcom does this. But eh... These would stop giving troubles when you
just put a 3.5MHz-signal on pin 42...
:-harddisk-interfaces; will probably have their own clock,
:or don't need one, but maybe....(take your guess)
That would be a **big**problem.
~Grauw
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