added info and links to pre-computed matrix files

README.md

@@ -117,9 +117,19 @@ cd <llama.cpp directory>
 # --chunks 100 (recommended)
 # --mlock : keep model in ram (only use if you had sufficient RAM for the whole fp16)
 ```
-4. Use the generated matrix file to quantise the model
+4. Use the generated matrix file to quantise the model (see further down for some pre-computed matrix files)
 ```
 ./quantize --matrix <output.matrix> <model_path>/ggml-model-f16.gguf <quantisation_level, eg:IQ4_XS>
 ```
 Note: normal quantisation also benefits from using a matrix file. It also seem that a bigger input matrix is
-better for higher quantisation.
+better for higher quantisation.
+
+### Pre-computed matrix files
+
+Since generating a matrix files takes time and requires significant processing power and memory,
+some kind folks have made available pre-computed matrix files. You can use those directly in the quantize process.
+However, remember they can only be used for the specific model mentioned, and no other.
+
+[Joseph717171/Imatrices](https://huggingface.co/Joseph717171/Imatrices) a growing list of many matrix files for 7B to 17B models
+
+[ikawrakow/imatrix-from-wiki-train](https://huggingface.co/datasets/ikawrakow/imatrix-from-wiki-train) matrix files for base models (lama, mistral, nous-hermes, qwen) trained on `wiki.train.raw`