repo: add readme

Signed-off-by: cocafe <[email protected]>

readme.md

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+# VCACHE-TRAY
+
+A tray utility to control dynamic CCD preference of heterogeneous AMD 3D V-Cache CPUs like 7950x3D and 7900x3D.
+
+![](./asset/preview.png)
+
+### Requirements
+
+- Install latest BIOS and AMD chipset driver
+- Option `CPPC Dynamic Preferred Cores` in BIOS `SMU menu` must be set to `AUTO` or `Driver` to allow OS control via `AMD 3D V-Cache Performance Optimizer` device
+  - Otherwise this device will not work and appear in Device Manager
+
+- Recommend to turn off `Game Mode` in Windows, since you are gonna use this utility to control CCD preferences and profiles manually
+
+
+
+### How to use
+
+Run it and switch modes via tray icon.
+
+if you need to add more or modify profiles, please edit the `config.json` and restart the utility.
+
+Pass `-h` to check more options, `--alloc_console` to check debug logs.
+
+⚠ Recommend switch the prefer CCD or setup profile firstly before starting new program, it looks like some activated threads will stick on original CCD until they are terminated.
+
+⚠ Only tested on Windows 10 yet.
+
+
+
+### How does it work
+
+While I was investigating 3D V-Cache driver and planning to take over control of device, but I found that AMD leaved a registry interface `HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\amd3dvcache\Preferences` to allow change things on the fly. It will take a **while**, like, up to serval minutes to take effect without restarting the 3dvcache service. That's it, this program is just a simple frontend of these registry interfaces.
+
+
+
+### Build
+
+Build with msys2 and cmake.
+