Iâm tring to write a comparative between MC68000 and 65c816 performance.
I always asumed that motorolaâs was far more powerful than SNES CPU. But I begin to doubt. :huh
According to MC68000 documentation, and 65c816 docs:
For a 16 bits add with carry instruction:
Register to register, takes 4 cycles on 68k. 65c816 does not support it.
Memory- Register: takes 8 cycles on 68k using (An) addressing mode, 12 using short absolute and 16 using absolute long.
It takes only 5 in 65c816 for absolute short, and 6 cycles for 65c816, stroing result in accumulator. Even suposing 68k runs at twice the MHz, it still will be faster (twice 6 is 12, so at 7.5MHz, as Genesis runs, SNES should be able to do the operation in 12 cycles, compared with 16 in Genesis).
If we then want to refresh the memory location with the result, we should add more cycles:
6 for SNES, when absolute long addressing mode.
16 for Genesis, for the same mode. Even taking account of the higher MHz count, it will be still behind.
These results confuse me a bit. Because they show that, at least, in this case (and also in some others, such as move/load or store instructions), 68k is not faster than 65c816.
68k only comes over 65c816 when operating with 32 bit values. But with a speed gain of 1.2 â 1.6, not more than 2 if we only consider clock frecuency.
What do you think about these results??
:smash
I always asumed that motorolaâs was far more powerful than SNES CPU. But I begin to doubt. :huh
According to MC68000 documentation, and 65c816 docs:
For a 16 bits add with carry instruction:
Register to register, takes 4 cycles on 68k. 65c816 does not support it.
Memory- Register: takes 8 cycles on 68k using (An) addressing mode, 12 using short absolute and 16 using absolute long.
It takes only 5 in 65c816 for absolute short, and 6 cycles for 65c816, stroing result in accumulator. Even suposing 68k runs at twice the MHz, it still will be faster (twice 6 is 12, so at 7.5MHz, as Genesis runs, SNES should be able to do the operation in 12 cycles, compared with 16 in Genesis).
If we then want to refresh the memory location with the result, we should add more cycles:
6 for SNES, when absolute long addressing mode.
16 for Genesis, for the same mode. Even taking account of the higher MHz count, it will be still behind.
These results confuse me a bit. Because they show that, at least, in this case (and also in some others, such as move/load or store instructions), 68k is not faster than 65c816.
68k only comes over 65c816 when operating with 32 bit values. But with a speed gain of 1.2 â 1.6, not more than 2 if we only consider clock frecuency.
What do you think about these results??
:smash