Measuring 30b CPU speed reduction

[Paul Dale]

(08-03-2015 05:16 AM)Sukiari Wrote:  What do you suppose the slow and fast speeds of the WP-34S firmware do to the battery? I always run mine with the slow setting by the way.

Marcus is the person to ask about this since he implemented the various speeds. I almost always use SLOW mode and once the battery voltage drops far enough, the 34S always runs in SLOW mode regardless of what you specify. Our low voltage handling seems to have a few quirks which have surprised people


My guess is that for normal (non-program) execution, it won't make too much difference. The CPU generally doesn't run for very long before returning to the low power idle states (we use two I think but it might be more). There are exceptions of course (some of the statistical functions being the main ones I'm aware of).

When running a program, SLOW mode will stress the battery less for the reasons Cyrille gave, although it isn't backing off anything like as far as the 30b does.


In light of Cyrille's comment, there is possibly some room for improvement in the 34S firmware -- slowing the clock down during a long run seems sensible -- this is trading battery life for performance but not in a linear fashion.


I don't remember Marcus mentioning anything about dynamically changing the wait state setting. The 34S seems to always use one wait state currently. SLOW mode on the 34S is 20MHz which is too fast to reduce the number of wait states (15MHz is upper limit for zero wait states according to the data sheet), however making SLOW mode 15MHz and getting rid of the wait states might be a win.


- Pauli