Hi all,
About the R800 clock speed...
I don't know it exactly. But I think the minimum clock cycle of
an instruction is 1/7MHz(140ns). In general, many CPU need higher
clock frequency than the instruction frequency. For example,
the external clock is devided by two and two different clocks(say ph1,ph2)
are generated. One is used for reading and another one is inverted and
used for writing. In the case of LD A,B instruction, read B by rising edge
of ph1 and write the value to A by rising edge of ph2 are executed in turn.
Anyway you need not to know that how many clocks are internally
used. If the system clock is 7MHz, I guess this means
that the fastest instruction is executed at 7MHz frequency.
>
> Another question... I'm interested on the Z380 project, but I have readed
> that, when the japanese companies planned to make the MSX2 (there are a few
> years!), they want to use the Z380... Is Z380 an old chip? Is a good choice?
>
Z380 is the only choice. It is the faster Z80 with enhanced instructions.
> Will be faster the Z380 than the R800? If is faster than the R800, it will
> be faster enough to allow the R800 emulation (for TR compatibility)?
>
Current Z380 works at 18MHz which corresponds to 7MHz of Turbo R.
However, the fastest instruction of Z380 needs two clocks(9MHz) as I remember.
Therefore, if you use only the fastest instructions, Z380 is slightly faster
than R800.
If 40MHz Z380 comes out, Z380 rules! I don't know when it will come out and
if it will or not.
I think the emulation of R800 is not good way. Even with 40MHz Z380, we cannot
obtain the R800 speed. Turbo R compatible will be impossible.
> And... what about omega project? I have emailed with Rafael Corrales, who
> works in the Z380 project, and it seems to work good, but I have heard
> nothing about Omega Project.
>
As I remember, the Omega project uses Z382 which uses I/O ports internally.
I doubt it is possible to make MSX compatible machine with Z382.
A lot of projects were announced. Jupiter project, Omega project,
MSX380 project, MMSX project, Genesis project... However,
None of them is realized. Or they don't want to inform the progress?
- Jun.
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