Re: A89: TI89 Site & Math-(not a serious responce)

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Re: A89: TI89 Site & Math-(not a serious responce)




> maybe in never-never land.  according to nintendo the gb and gbc are 1 and
2
> MHz respectively, but that's measured in instructions per second.  if you
> measure it in t-states per second (the way zilog does for god knows what
> wacked out reason) then the gb and gbc variations are 4 and 8 MHz
> respectively.  compared to the 68000 in the 89 (10MHz), the double speed
> mode on the gbc is still 8MHz slower than the 89 and a ti-8x is about 8.5
> MHz slower than the 89/92/92+ (assuming that motorolla measures frequency
by
> instructions per second as most normal companies do ;-)

This is not entirely correct. Mhz is no means of measuring instructions per
second.
And it is also no means of measuring processor speeds.

Some IT salespeople created the acronym MIPS which stands for "Million
Instructions
Per Second".( Some people say it stands for "Meaningless Information
Provided by
computer Salesmen" ;) And i guess they are correct )

The Z80 requires 4 machine cycles for every instruction cycle.  Thus the
real clock is
four times smaller than the external clock. But in addition the Z80 doesnt
execute
every instruction in a single instruction cycle. Some instruction take
multiple cycles.
(Probably the minumum is something like two.. I dont know it off head.) This
means
that in a real word application far less than 1 million instructions are
executed on a 4Mhz
Z80. So it does less than 1 MIPS.

The same goes for the 68000. The minimal cycle count per instruction is 4.
But this is
only true for very simple instructions. It can go as high as 158 cycles for
a signed
divide. In real life applications the 68000 at 10 Mhz reaches something like
~1.7 MIPS.

But this does still not mean that the 68000 is just 2 times faster than a
Z80.

The 68000 instruction set is far more efficient than the Z80 ones. Also the
68000
is able to handle 32 bits at once.

For example multiplying two 16 bit integers takes a single instruction on
the 68000 while it
requires a complicated loop on the z80.
References: