RPN83P: RPN calculator for TI-83+ TI-84+ inspired by HP-42S

[bxparks]

(11-30-2023 09:57 AM)ebs Wrote:  Have you checked the battery consumption at 15 Mhz? If it's going to draw it quickly maybe you can do the frequency user selectable?

I have not, but it would interesting (Though I'm having some difficulty imagining how I would build a contraption that could inject an ammeter into the circuit in the AAA battery compartment. A thin insulator with 2 conductors on either side, with metallic tabs?).

My guess is that the battery consumption is not an issue because:

• These TI calculators are configured to run normally at 15 MHz. The OS runs at 15 MHz. The TI-BASIC programs run at 15 MHz. It's only when they are asked to run user-uploaded assembly language programs (ASM() function) or flash apps (APPS button) that the calculator switches to 6 MHz for backwards compatibility.
• Even if the power consumption is higher at 15 MHz (let's say, at least 2.5X more, probably a little more), the computation finishes 2.5X faster. The relevant quantity is the amount of computation per Joule (energy), not per Watt (energy/second). My guess is that TI chose to configure these Z80 processors at 15 MHz, because the computation per Joule was roughly the same as 6 MHz. Otherwise, the calculators would consume the batteries significantly faster.
• The RPN83P program spends the vast majority of its time in the GetKey() OS function just waiting for a key press from the user. My guess is that the Z80 goes into a deep sleep mode, and waits for an interrupt from the keyboard. So even if the processor uses slightly more than 2.5X power at 15 MHz, it spends only a small amount of time at the higher burn rate.