ZoomMultistompZDL

ZD2 port research — September 14, 2026

Status: notes only. No ZD2 build, effect port, dependency installation, or pedal write was performed for this investigation. Our released pack remains ZDL-only; PE has not gained Plus-series patch support.

New evidence

zoom-zt2 issue 93 starts with extracting and disassembling LineSel in 2025. The later July 2026 discussion links to Stomphacks, a working C-to-ZD2 pipeline. Its author reports hardware testing of gain and three routing effects on MS-70CDR+ units. This is upstream evidence, not a test performed by us.

Stomphacks generates the effect container and code, uses zoom-zt2 for file/MIDI handling, and uses TI C6000 tools 8.5.0, the compiler version already installed for this repository. Its existence supersedes our earlier question about whether custom ZD2 effects are possible on that model. It does not make ZDL binaries interchangeable with ZD2 or prove support for every Plus pedal.

Interface findings relevant to our pack

The upstream ABI documentation reports the following for MS-70CDR+ firmware 1.20:

• Audio receives separate instance and context pointers; the effect bus is ctx[1]. Blocks contain 16 frames per channel at 44.1 kHz, compared with our ZDL kernels’ 8-frame channel blocks. Port the entry adapter and loop sizes.
• Coefficients are in instance[1]; small per-instance state is in instance[2]. The documented proven state floor is 192 bytes, not a maximum.
• Init invokes every edit handler to restore stored parameter values, including after chain edits. This closely parallels our parameter-materialization fix.
• The documented relocations are ABS32, ABS_L16 and ABS_H16. Runtime helper references must resolve inside the effect. Our linker is not a drop-in ZD2 builder merely because it handles related C6000 relocations.
• Delay-line memory at instance[3] is outside that document’s established contract. The issue’s suggestion that it resembles our three-word ZDL buffer descriptor is explicitly unconfirmed for Plus hardware. Do not assume our observed arena size transfers to ZD2.

Our older build/ABI.md LineSel cross-reference predates this documentation. Its register-derived context labels should be reconciled with the separate instance/context model before implementation, not copied into a port verbatim.

The routing writeup and issue discussion also describe Split/Swap/Merge using the output bus as a parallel path. That is an optional future feature, separate from porting our DSP.

Proposed sequence — not started

1. Inspect and pin an upstream Stomphacks revision; reproduce its gain build locally and review the generated validation report.
2. Compare its entry points, coefficients, bypass and init behavior with ours.
3. Select a small effect after measuring its state requirements; port and test that one before considering a whole-pack conversion.
4. Establish delay-memory ownership, size and isolation across multiple slots before Stasis, Rooms, Spool or other buffer-heavy effects.
5. Investigate PE’s Plus-series patch protocol independently, using documented commands or captured traffic rather than guessing command bytes.

Before any hardware trial, review the upstream safety procedure. The author reported bricked units during development. Its procedure centers on confirmed autosave-off, backups, scratch patches, readback comparison and cleanup. No hardware trial is authorized or implied by recording these notes.

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