docs: get started on detailed multi-backend guide

docs/source/_toctree.yml

@@ -12,6 +12,8 @@
     title: 8-bit optimizers
   - local: algorithms
     title: Algorithms
+  - local: non_cuda_backends
+    title: Non-CUDA compute backends
   - local: fsdp_qlora
     title: FSDP-QLoRA
   - local: integrations

docs/source/non_cuda_backends.mdx

@@ -0,0 +1,27 @@
+# Multi-backend support (non-CUDA backends)
+
+As part of a recent refactoring effort, we will soon offer official multi-backend support. Currently, this feature is available in a preview alpha release, allowing us to gather early feedback from users to improve the functionality and identify any bugs.
+
+At present, the Intel CPU and AMD ROCm backends are considered fully functional. The Intel XPU backend has limited functionality and is less mature.
+
+Please refer to the [installation instructions](./installation#multi-backend) for details on installing the backend you intend to test (and hopefully provide feedback on).
+
+> [!Tip]
+> Apple Silicon support is planned for Q4 2024. We are actively seeking contributors to help implement this, develop a concrete plan, and create a detailed list of requirements. Due to limited resources, we rely on community contributions for this implementation effort. To discuss further, please spell out your thoughts and discuss in [this GitHub discussion](https://github.com/bitsandbytes-foundation/bitsandbytes/discussions/1340) and tag `@Titus-von-Koeller` and `@matthewdouglas`. Thank you!
+
+## Alpha Release
+
+As we are currently in the alpha testing phase, bugs are expected, and performance might not meet expectations. However, this is exactly what we want to discover from **your** perspective as the end user!
+
+Please share and discuss your feedback with us here:
+
+- [Github Discussion: Multi-backend refactor: Alpha release ( AMD ROCm ONLY )](https://github.com/bitsandbytes-foundation/bitsandbytes/discussions/1339)
+- [Github Discussion: Multi-backend refactor: Alpha release ( Intel ONLY )](https://github.com/bitsandbytes-foundation/bitsandbytes/discussions/1338)
+
+Thank you for your support!
+
+## Benchmarks
+
+### Intel
+
+### AMD