rtt_timing, B done

examples/rtt_timing.rs

@@ -98,18 +98,42 @@ Because we need to acount for the fact that the counter might have wrapped aroun
 // > cargo run --example rtt_timing --release
 //
 // [Your answer here]
+/*
+70001 cycles
+*/
 //
 // B.2) How many cycles per iteration?
 //
 // [Your answer here]
+/*
+Only running timng for the content of the for loop:
+    let mut start: u32 = 0;
+    let mut end: u32 = 0;
+    for _ in 0..10000 {
+        start = DWT::get_cycle_count();
+        asm::nop();
+        end = DWT::get_cycle_count()
+    }
+You get 6 cycles.
+But the total number of cycles divided by the loop iterations is 7,0001 ~= 7 cycles.
+
+*/
 //
 // What is the speedup (A/B)?
 //
 // [Your answer here]
+/*
+A/B = 4790151/70001 = 68,429751 ~= 68
+We get a speedup of about 68.
+*/
 //
 // Why do you think it differs that much?
 //
 // [Your answer here]
+/*
+My guess is that there is a lot of code add in the compilation of the debug version that enables you to debug the code en a meaningfull way.
+I.e there is no optimizations, no removal of uneccesary code no nothing.
+*/
 //
 // ------------------------------------------------------------------------
 // In the loop there is just a single assembly instruction (nop).