At 01:41 PM 6/16/98 +0200, you wrote:
>:What is the S1990?? :-?
>:Then... you have an Turbo R with the 7MHz Z80? It is a wonderful computer!
In turbo R the R800 runs on 7MHz, the Z80 on 3.5MHz. But the R800 is a lot
faster than 7MHz Z80 because it takes less clockticks per instruction and
it has built-in cache.
>Anyway, I foresee problems when a faster MSX, i.e. a
>MSX with the Z380 onboard, will be released. New programs will then also
>support the Z380-drivers, but old programs will think it's a turboR and use
>the turboR-drivers, which access the MoonSound way too fast on a Z380.
That is something the designers of the Z380 board will have to fix.
For example, they can use a very low clock speed to emulate Z80 behaviour
(something like 1MHz, because Z380 uses less clockticks per instruction
than Z80 does). This is not a good way of solving the problem, but it's
very easy to implement.
A good way would be to delay the Z380 on I/O to the old-style MSX bus. Just
like what the S1990 does to the R800 on VDP I/O. Ofcourse the new bus will
work with much lower delays (or even no delays at all), so you can use the
Z380 system at full speed if you use high-speed hardware connected to the
new bus.
If you use Z380 top speed with only I/O slowed down, most programs will
work fine. DOS and BASIC will be much faster, but games usually run at the
same pace because they are programmed on the interrupt. Except for SD
Snatcher and Solid Snake (just use 7MHz or R800 speed and you'll see what I
mean).
Bye,
Maarten
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