Cycle-perfect emulators at least for typical 8- and 16-bit systems need to run each emulator subsystem (CPU, video, audio, ...) in lock-step for each clock cycle. Spreading those emulator systems over multiple threads would mean that the threads need to synchronize with each other after each step (which is just a few host CPU instructions long). It might be easier for more modern hardware where subsystems are much more decoupled from each other (and I guess with Moore's Law dead this is our only hope to emulate more modern hardware in the future).
That's true. In the case of Nintendo DS, I'm aligning doing line-based emulation; so I first serially emulate the two CPUs (I could in theory parallelize then, but I haven't properly design the emulator around this, so all memory-mapped callbacks are not concurrent safe), and then emulate the graphic subsystem for a single line, spreading the different layers across different goroutines.
This means that goroutines synchronize 263*60 times per second, which is something. I measure a high contention, so I'm not even sure it was worth in the end, but I thought it was a good experiment to attempt :)
where I configure the memory-mapped registers of the interrupt controller; "wcb" / "rcb" tags stand for write/read callbacks, which means that specific callbacks (with names matching the register names) will be called for each read/write operation; this is all achieved through reflection. The same applies to mapping the whole register bank, which is done here:
https://github.com/rasky/ndsemu/blob/master/nds9.go#L69
The memory subsystem handling these and more features is in emu/hwio, and I'm actually pretty proud of it. For the memory mapping itself, a radix tree is built which is quite quick to lookup and doesn't require much barcoding.
In fact, the whole "emu" package is a generic framework for emulators in Go, and I plan to reuse it in the future :)
The Octalyzer has separate threads for cpu, sound, memory, networking, graphics and the main opengl loop. We use vertical blanking and sound timing to keep it all in sync.
