A few years ago, I got interested in Forth due to its connection to RPN calculators but lost interest because of the huge hit to performance a stack-based system takes on an architecture like 6502. Recently, my interest was piqued again during a conversation in the #Forth IRC channel on FreeNode about Mecrisp-Across, which uses an ARM-based microcontroller board to produce optimized assembly for the MSP430. Because the compiler tries to keep values in registers instead of the stack, it has the potential to reclaim some of the performance lost in most Forths. Some of these optimizations might be useful for a 6502-based Forth, so I tried to understand how optimizations in Mecrisp work.
The first step was getting Mecrisp running on a PC. The author provides versions that are compiled for ARM with Linux system calls, so you can use QEMU for emulation under Linux. Getting this working on Windows was a real challenge. One Debian image I tried emulating with QEMU crashed the emulator outright. Another image booted into Linux but refused to install QEMU complaining about needing the Linux CD in the drive before it would install any packages. Getting Ubuntu working on VirtualBox under Windows 10 and installing QEMU on it wasn't too tough, but the Mecrisp image wouldn't run until I got the right type of QEMU (there are several). The right combination was VirtualBox, an Ubuntu image from OSboxes, and QEMU-user-static.
