Okay, the Visual BASIC code I used as a starter was wrong, but the article says the Apple II calculated 38 and the BBC Micro calculated 70.
I'm guessing they are using very large integers from assembly to avoid errors... which is the whole point of the benchmark.
BASIC cuts off the number of digits so it isn't really doing the same thing. FWIW, it overflows at 185 on an MC-10 in 10 seconds.
Based on their numbers, it would require about a 14MHz 6502 to hit 500. I think there were a few running that fast in the late 80s.
There definitely are now.
The 6803 and 6809 only have a 16 bit ADD and 8 bit ADC, as well as no instruction prefetch, so they may not perform as well as the 6502 on this.
The 6303 would do slightly better than the 6502 because it has an instruction prefetch, but it's a small amount.
The 6309 has 32 bit ADD and 16 bit ADC instructions as well as the instruction prefetch, so it might double the BBC number.
Edited by JamesD, Tue Mar 6, 2018 11:55 AM.