Re: Raspberry Pi 3 & 3+ speed issues

>> So they're basically both running at the same speed. At 600 MHz, they both
>> take about 24.5 seconds to count the first million prime numbers, meaning
>> that the Pi 3+, which says it's running at 1400 MHz, is really running at
>> 1200 MHz.
>
> Maybe another test shows a difference. If that 'primes' program is
> a common sieve, it will be limited by memory speed, and that is the
> same for pi3 and pi3+.

It counts primes in cache on most CPUs, so I use it to gauge clock speeds, 
even "turbo burst" speeds, by comparing it with results from known clock 
speeds. It's good to ask, and I should've mentioned the kind of counting, 
but even if it were memory bound, the count running at 600 MHz wouldn't be 
exactly half the speed of it running at 1200 MHz :) [1]

dry2 of 10000000 runs:

Microseconds for one run through Dhrystone:    0.3
Dhrystones per Second:                      3436426.0

Microseconds for one run through Dhrystone:    0.3
Dhrystones per Second:                      3424657.5

That's the same, too.

Does anyone out there with a Raspberry Pi 3+ want to check their results 
at (supposedly) 1400 MHz?

John


[1]:

/* Find the nth prime.
    John Klos, [email protected] */
#include <stdio.h>
long a=1000000, b=4, c=7, d, e, f=4, g=4, h=4, i=9;
int main() {
  while (b<a) {
   c+=f;
   d=1;
   f=6-f;
   g=4;
   if(e<c) {
    h++;
    e+=i;
    i+=2;
   }
   if(e==c)
     d=c;
   while (d<h) {
    d+=g;
    g=6-g;
    if (!(c%d))
     d=c;
    }
    if (c!=d)
     b+=1;
  }
  printf("%ld, %ld\n",b,c);
}