Nonpareil status

[brouhaha]

(10-24-2022 04:53 PM)eshazen Wrote:  Next I think I may revive my plan to port at least the woodstock simulator to Z80 assembly, as my compiled C code is a bit slow.

I'm not surprised. When Rich Ottosen and I were building calculator prototypes, we initially used Microchip PIC16 and PIC18 8-bit processors. At that time (mid to late 1990s), the available C compilers produced code that was far too slow, so we did that all in assembly. More recent PIC compilers are better, though for Microchip XC8 one unfortunately must buy a license or subscription to get full optimization. I think it would make sense with that to keep most of the simulation in C, but recode portions of it (especially the arithmetic instructions that work on a range of digits within a word) in assembly. That might also make sense for other 8-bit micros, including the Z80.

Around 2010 we switched from PIC microcontrollers to ARM Cortex-M3, specifically the Energy Micro (now Silicon Labs) EFM32 Gecko and Giant Gecko, and used C code exclusively. At the time, those were the only ARM microcontrollers that had decent memory size and very very low power consumption. (The Atmel AT91SAM7L128 used in the first ARM-based version of the HP-12C was low power, but only had 2K of battery powered RAM.) Rich was pretty skeptical of the low-power claims Energy Micro was making, so before he was willing to lay out a board, I bought the EFM32DK board, which was a rather fancy development board that had built-in current profiling with a graphical LCD display, and was quickly able to demonstrate that the power consumption of our calculators using an EFM32 would be very similar to those using the "XLP" PIC microcontrollers.

Now there are a lot more choices for low-power ARM microcontrollers, including the ATSAM4LC2CA used in the newer HP-12C and the STM32L476 used in recent Swiss Micros calculators. However, I understand the appeal of building projects using old-school microprocessors, as I do a lot of such projects myself.