zeroone wrote:
Are there any side effects to fully resetting the APU on reset? Will any games actually break?
Except for $4017 the registers are write only. I think the only way it can affect anything but sound is through an IRQ? (DPCM and/or Frame Counter.)
So... the consequences of an incorrectly initialized APU are quite low, especially since it's silenced by the reset.
lidnariq wrote:
No, the noise LFSR is left as-is. It just comes out of a cold boot all 0, like most other things in the CPU. (due to how NMOS works, I suspect.)
Ah, thanks for the clarification.
lidnariq wrote:
To briefly summarize: Of the 312 nodes that are cleared during reset, (at least) 161 are given names in Visual2A03:
* frame_irq (acknowledging the IRQ but not disabling it)
* frm_c
* snd_halt
* spr_addrX (to cleanly abort an in-process DMA, I assume)
* sq0_cX, sq0_envcX, sq0_envtX, sq0_lenX, sq0_on, sq0_swptX, sq0_tX
* sq1_cX, sq1_envcX, sq1_envtX, sq1_lenX, sq1_on, sq1_swptX, sq1_tX
* tri_cX, tri_lcX, tri_lenX, tri_on, tri_tX
* noi_envcX, noi_envtX, noi_lenX
* pcm_aXX, pcm_bitsX, pcm_en, pcm_irq, pcm_lcXX, pcm_on
Interesting!