using intel i5 freqency governors

[Lee <ler762@gmail.com>]

The short story is that I have an Intel i3 windows 10 desktop with
cygwin installed and an Intel i5 debian desktop.  One of my scripts
takes about 10 minutes to run on the windows/i3 and 15 minutes on the
debian/i5!  ick

if i do
$ sudo cpupower frequency-set -g performance

then it takes about 10 minutes to run the script on the i5, **but**
the cpu frequency never drops down to power-saving mode when the
machine is idle - eg
$ sudo cpupower -c all frequency-info | grep 'call to kernel'
  current CPU frequency: 3.99 GHz (asserted by call to kernel)
  current CPU frequency: 3.95 GHz (asserted by call to kernel)
  current CPU frequency: 4.01 GHz (asserted by call to kernel)
  current CPU frequency: 3.91 GHz (asserted by call to kernel)
  current CPU frequency: 3.96 GHz (asserted by call to kernel)
  current CPU frequency: 4.00 GHz (asserted by call to kernel)

and more annoying, setting the frequency governor back to powersave
doesn't seem to drop the frequency all that much

$ sudo cpupower frequency-set -g  powersave
Setting cpu: 0
Setting cpu: 1
Setting cpu: 2
Setting cpu: 3
Setting cpu: 4
Setting cpu: 5

$ sudo cpupower -c all frequency-info | egrep 'call to kernel|The governor'
                  The governor "powersave" may decide which speed to use
  current CPU frequency: 3.85 GHz (asserted by call to kernel)
                  The governor "powersave" may decide which speed to use
  current CPU frequency: 3.58 GHz (asserted by call to kernel)
                  The governor "powersave" may decide which speed to use
  current CPU frequency: 4.01 GHz (asserted by call to kernel)
                  The governor "powersave" may decide which speed to use
  current CPU frequency: 3.55 GHz (asserted by call to kernel)
                  The governor "powersave" may decide which speed to use
  current CPU frequency: 3.66 GHz (asserted by call to kernel)
                  The governor "powersave" may decide which speed to use
  current CPU frequency: 3.57 GHz (asserted by call to kernel)


How do I get the intel cpu "turbo boost" fully engaged when I'm
running my script and go back into power save mode when the machine is
idle?

Thanks
Lee