] Then, I think that R800 works at 28 MHz (it has a clock of 28MHz). I don't
] know the MIPS (Milions of Instructions Per Second) of the R800, but probably
] the ratio MHz / MIPS is near 1 (that means between 1 and 2), because of the
] RISC architecture. But R800 is RISC, and that means that it needs to execute
] one or more instructions to do the same functionality of one only
] instruction of the Z80.
R800 is RISC compared to the real CISC processors like 68000 and 80386 and
above. But that is also true for the Z80. The Z80 may have had many
instructions when it was designed in 1977 but that is nothing compared to the
processors of the mid 80'ies and later. In fact, the R800 is completely
opcode compatible with all official Z80 instructions. You can regard it as a
redesign of the Z80. The only new thing about it is that some unofficial Z80
instructions (especial with the IX/IY registers) have been made official. And
that some multiply instructions have been added. And that some unofficial Z80
instructions (the four byte indirect HL load instructions for example) have
been removed.
And the clock speed thing, well, it completely depends on how you look at it.
The clock cristal has a frequency of 28.64 MHz indeed. And it is divided by
four to get a 7.16 MHz bus speed. And whether the R800 runs internally at
28.64 MHz or at 7.16 MHz? I can't tell you. I know a lot about the R800 which
I have concluded from low level software tests which I have done using test
routines written in assembly. But I do not have the R800 blueprints. Nor do I
have an electron microscope to examine the circuitry. Though, I do have the
service manual of the GT with the drawings of the MSX turbo R and one can
also conclude a lot from those schematics.
Best regards,
Alex
--
Alex Wulms/XelaSoft - MSX of anders NIX - Linux 4 ever
See my homepage for info on the *** XSA *** format
http://www.inter.nl.net/users/A.P.Wulms
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