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AN-001: 65xx, x86, and 68K Instruction Level Performance Comparisons


Did you ever wonder why the popular early PC’s (Apple, Acorn, Atari, and Commodore) and video games (Atari, Commodore, and Nintendo) were built on 65xx technology rather than on Intel x86 or Motorola/Freescale 68K technology?

Take a look at the 65xx 8–bit and 8/16–bit microprocessor execution speeds on an 8-bit data bus in the table below compared to the Intel x86 and Motorola MC68000. Now you know! Also, the performance of the x86 and the 68K were on a 16-bit data bus! The PC (x86) and Mac (68K) ran less than 8MHz memory bus speed when first introduced.


Comparison of Execution Speeds in Microseconds
at 8MHz Operating Frequency
Operation Data Type WDC
65C02S
WDC
65C816S
Intel
x86
Motorola
MC68000
Register to register move Byte/word
double word
0.25/0.50
1.00
0.25/0.25
0.50
0.25/0.50
0.50
0.50/0.50
0.50
Memory to register move Byte/word
double word
0.38/0.75
1.50
0.38/0.50
1.00
2.12/2.12
4.25
1.50/1.50
2.00
Add memory to register Byte/word
double word
0.38/0.75
1.50>
0.38/0.50
1.25
4.37/4.37
8.75
2.50/2.50
3.75
Compare memory to memory Byte/word
double word
0.75/1.50
3.00
0.75/1.00
2.00
2.25/2.25
4.50
1.50/1.50
2.25
Conditional branch branch taken
not taken
0.38
0.25
0.38
0.25
1.00
0.50
1.25
1.00
Modify Index branch if zero branch taken 0.62 0.62 1.37 1.25
branch to subroutine branch taken 0.75 0.75 2.37 2.25
Interrupt latency Interrupt 1.25 1.50 22.75 21.75
Comparison of Execution Speeds in Seconds at 8MHz Operating Frequency
Operation Data Type WDC
65C02S
WDC
65C816S
Intel
x86
Motorola
MC68000
Sieve of Eratosthenes N/A N/A .78 1.90  



  

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Last updated 10/11/2016
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