amd-vram-detection

Read the true VRAM size of a GPU on Windows from Python — working around the WMI value that silently caps at 4 GB. Single file, stdlib only.

> python vram.py
AMD Radeon RX 6600 XT: 8.0 GB (8589934592 bytes, qwMemorySize)

The problem

The standard way to read VRAM without third-party packages is WMI/CIM:

Get-CimInstance Win32_VideoController | Select Name, AdapterRAM

Win32_VideoController.AdapterRAM is a uint32 — it physically cannot represent more than ~4 GB. Every modern GPU with more VRAM reports 4,293,918,720 bytes (or overflow garbage). This is a long-documented WMI limitation, not a driver bug.

NVIDIA users can shell out to nvidia-smi. AMD ships no equivalent that is reliably present, so on AMD machines a Python program asking "how much VRAM does this box have?" gets a wrong answer from every obvious API.

The workaround

The display driver writes the real 64-bit value into the GPU's display class key in the registry:

HKLM\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\<0000...>
    DriverDesc                          = "AMD Radeon RX 6600 XT"
    HardwareInformation.qwMemorySize    = REG_QWORD, VRAM in bytes

Each numbered subkey is one display adapter. vram.py enumerates them with winreg, matches DriverDesc, and reads the QWORD — correct for >4 GB cards. A legacy 32-bit HardwareInformation.MemorySize fallback is read (and labelled as possibly capped) when the QWORD is absent, e.g. under very old drivers.

Installation

There is nothing to install — it's one file, stdlib only (Python ≥ 3.7, Windows). Copy vram.py into your project and import it, or run it directly. No pip, no dependencies.

Usage

python vram.py               # list every display adapter + true VRAM
python vram.py "RX 6600"     # filter by name substring

As a library:

from vram import list_display_adapters, get_vram_bytes

get_vram_bytes("RX 6600")     # -> 8589934592
list_display_adapters()       # -> [{"name": ..., "vram_bytes": ..., "vram_gb": ..., "source": ...}]

Limitations

• Windows only (registry). --help runs anywhere; everything else needs winreg.
• Reads what the driver reported at install time; a software/virtual adapter has no size value (reported as such, not guessed).
• Verified on AMD (Adrenalin) hardware. NVIDIA/Intel drivers also write this key, but if you have nvidia-smi/NVML available, prefer those on NVIDIA.

Requires Python ≥ 3.7. No dependencies.

Staying up to date

To be notified of new releases, Watch this repo on GitHub → the Custom dropdown → check Releases. The full list lives at github.com/casul185/amd-vram-detection/releases.

vram.py also checks for updates itself: on a normal run, at most once per 24h, it makes a best-effort call to GitHub and, if a newer release exists, prints a single one-line notice to stderr. It never auto-updates and never nags. To disable this entirely, set AMD_VRAM_NO_UPDATE_CHECK=1 in your environment.

Support

If this project is useful to you, you can support it at ko-fi.com/casul185.

License

MIT — see LICENSE.

Used by

frameseer uses this to read true GPU VRAM for its performance recommendations.