Memory

Teensy 4.1 memory is easy to exhaust in RAM1 (DTCM) even when PSRAM is free. The firmware deliberately parks large structures in slower memories.

Regions (practical view)

Region	Keyword	Use for
RAM1 / DTCM	(default)	Hot code, small frequently touched state
RAM2	DMAMEM	DMA-friendly buffers, some audio/FX state
PSRAM	EXTMEM	Large grids, Device SMP, bulky Audio objects

Patterns already used

• EXTMEM Note note[...] — pattern grid
• EXTMEM Device SMP — project/session bag
• EXTMEM on many Audio mixers/oscillators in audioinit.h
• DMAMEM for some float tables (detune, channelOctave, …)
• Freeverb DMA buffers via effect_freeverb_dmabuf

Anti-patterns

• Large static locals inside functions → still land in RAM1
• Growing String members in big tables → heap + RAM pressure (slider names were moved to PROGMEM index tables for this reason)
• Duplicating the note grid “temporarily” on the stack/DTCM

When you add features

Ask: does this buffer need single-cycle DTCM access every sample? If not, prefer EXTMEM/DMAMEM. If you have _internal-docs/RAM1_OPTIMIZATIONS.md locally, it lists concrete reclaim wins already applied.