Actual speed (CPU clock frequency) of 34S?

[Tugdual]

(04-15-2014 08:31 PM)Marcus von Cube Wrote:  

(04-15-2014 02:27 PM)Waon Shinyoe Wrote:  We know that 34s(or 30b) has the ARM7 core which clocks 32kHZ to 40MHz . But I wonder how fast it really is, since it's limited by the power supply?

You've answered the question yourself. When I first started the hardware port of WP 34S I just left power consumption out completely: No problem because my prototype device uses a wall wart as its power supply.

Things are completely different with two coin cells as the sole source of power. The software is constantly switching between the various oscillators and speeds, depending on the task the calculator is performing and the time already spent on it. When you look at a steady display without a program running, the processor is essentially switched off. A wake up call (through the keyboard) speeds it up slightly, just enough not to appear too sluggish in accepting key strokes. When a function is executed, speed is raised to about 10 MHz for a fraction of a second. If things are taking longer, speed is increased to the full 32mHz until the task is completed or the voltage drops too much which causes a speed decrease to some 10 MHz again.

As you can see, knowing the maximum specs of the chip doesn't give you enough information about the actual time a calculation will take.

The code itself isn't optimized for speed either. Many of the advanced functions are written as key code sequences in order to save valuable flash space. Adding the 34 digit accuracy of most functions to the mix may explain why some other calculator with a less powerful CPU can outperform the WP 34S in certain benchmark cases.

Hi Marcus, quick question. What governs the frequency switch? Is that hardware or software?