Development

Verify your card

⚠️ Undervolting is validated only on RTX 5090 (Blackwell). The tuning-buffer byte offsets are hardware-specific, so on any other generation confirm it works before relying on it.

The read path checks itself: status (and undervolt) validate that the V/F curve decodes as a real NVIDIA table, and warn or refuse if the offsets don’t fit your card. So to confirm a card you only need to check the harder write path — that a change actually lands and reverts:

1. Run status. If it prints no layout warning, the read offsets fit your card. (layout shows the detected offsets explicitly if you want to see them.)
2. Under a sustained 3D load, apply a small change and read it back, then undo it:

   simple-nvidia-undervolt undervolt --mv 950 --mhz 2800 --no-persist
   simple-nvidia-undervolt status     # the core curve offset should now be non-stock
   simple-nvidia-undervolt clear      # back to stock
   

   If the undervolt applies, status shows the offset, and clear removes it, the write path works — the card is confirmed. Please open an issue/PR so the generation can be marked supported.

3. If status warns or undervolt refuses, the offsets don’t match this card. Port them with the advanced steps below.

Build

dotnet build src -c Release
src/bin/simple-nvidia-undervolt.exe status
dotnet test tests   # pure-logic unit tests (no GPU required)
dotnet test e2e     # real GPU read/write tests; run as Administrator (see e2e/README.md)

The e2e project drives the real driver (writing tuning and reading it back). Its tests skip unless the host is elevated with an NVIDIA GPU, and they restore the tuning they find — see e2e/README.md.

For a standalone, single-file executable with no .NET runtime dependency, publish with Native AOT (needs the Visual C++ build tools / vswhere.exe on PATH):

dotnet publish src -c Release
src/publish/simple-nvidia-undervolt.exe status

Diagnostics

For inspecting the NVAPI tuning structs and confirming the layout on a given card. These are hidden from the main --help; run --help-diagnostics to list them.

curve                       Dump the live V/F curve.
layout                      Detect the status-curve offsets and check them against the build.
voltage                     Live core voltage/clock/temp/power, one-shot (continuous is 'watch').
clocks                      Current/base/boost clocks.
scan <value>                Find a value across the tuning buffers.
snapshot / diff             Capture buffers, then show which words a change moved.
probe <hexId>               Find accepted (version, size) pairs for a function.
extent <hexId> <v> <sz>     Measure the real struct size the driver writes.
raw <hexId> <v> <sz>        Dump the 32-bit words a GET writes.

The curve lives in two index-aligned buffers: the status (0x21537AD4 v1, 28-byte entries, freq +0x08 / volt +0x0C) holds the live effective curve; the control (0x23F1B133 v1, 36-byte entries, signed kHz delta +0x18) holds the editable deltas. A control entry drives the next status anchor (so anchor i ← control i-1). The status freq column collapses at idle, but the voltages stay valid.

Porting the offsets to a new card

Curve handling depends on byte offsets in src/NvApi.cs:

control: base 0x64  stride 36  delta +0x18   (size 9248)
status:  base 0x40  stride 28  freq +0x08  volt +0x0C   (size 7208)

The status (read) offsets are detectable: run layout. It finds them from the live curve and prints them next to the build’s; under a 3D load it confirms the freq column too. Paste any differing values into the Status* constants and rebuild.

The control (write) offsets carry no voltage to anchor on, so derive them with a write, in an Administrator terminal:

1. clear, then snapshot.
2. In Afterburner’s curve editor (Ctrl+F) raise one point (e.g. 950 mV) and flatten to its right; Apply.
3. diff — the changed curveControl words give the stride (their spacing) and the delta offset; the run starts at control entry i-1 for the lowest moved status anchor i (skip the i-1 and writes land one anchor off). Set the Ctrl* constants and rebuild.

Then re-run Verify your card above; if both the read check and a write round-trip hold, please open an issue/PR so the generation can be marked supported.