What is the KIPS rate of the 6502 in the VCS?

[potatohead]

Wondering about instructions per second on average.

 

That's it.

[Thomas Jentzsch]

Most instructions take between 2 and 5 cyles, so maybe ~3.5 cycles on average. Which results into about 300k instructions/second.

[Kurt_Woloch]

Hmmm.... well, here's a rough calculation:

 

The 6502 steps through the code one byte per cycle, but stops if data access has to be done. Also there are some instructions which take an additional cycle to process something internal (for instance, INX and INY take 2 cycles although they are only 1 byte long and don't transfer data over the bus).

So let's assume that the average instruction is 2 bytes long and takes 1 additional cycle for a data transfer. In this case, the average instruction would take 3 cycles to process. Since a cycle on the 2600 takes 840 nanoseconds, we have one instruction occuring every 2,52 microseconds, which would give about 397 KIPS. But that's only a rough estimation.

[potatohead]

Thanks!

 

I was just wanting a sanity check.