diff --git a/dev/repackage_data_reference.py b/dev/repackage_data_reference.py
index 32980a8..0ec61b4 100644
--- a/dev/repackage_data_reference.py
+++ b/dev/repackage_data_reference.py
@@ -1,5 +1,5 @@
 """
-Repackage the FinewebEdu-100B dataset into shards:
+Repackage a given dataset into simple parquet shards:
 
 - each shard is ~100MB in size (after zstd compression)
 - parquets are written with row group size of 1000
@@ -10,6 +10,16 @@ The big deal is that our DataLoader will be able to stream
 the data and cache it along the way on disk, decreasing the
 training latency.
 
+Historical context:
+Originally, nanochat used the FinewebEdu-100B dataset.
+Then we switched to the ClimbMix-400B dataset due to superior performance.
+This script documents how both were prepared.
+
+The outputs are here:
+
+https://huggingface.co/datasets/karpathy/fineweb-edu-100b-shuffle
+https://huggingface.co/datasets/karpathy/climbmix-400b-shuffle
+
 NOTE: This file is meant only as reference/documentation of the
 dataset preparation and it is not used during the project runtime.
 """
@@ -20,12 +30,37 @@ from datasets import load_dataset
 import pyarrow.parquet as pq
 import pyarrow as pa
 
+# You can change these:
+dataset_tag = "climbmix"
+upload_to_hf = True
+
+# Dataset configurations:
+if dataset_tag == "fineweb_edu":
+    dataset_kwargs = {
+        "path": "HuggingFaceFW/fineweb-edu",
+        "split": "train",
+        "name": "sample-100BT", # ~100B GPT-2 tokens at ~3 chars/token => ~300B chars total
+    }
+    output_dirname = "fineweb_edu"
+    data_column_name = "text"
+    tokenizer = None
+    upload_tag = "fineweb-edu-100b-shuffle"
+
+elif dataset_tag == "climbmix":
+    import tiktoken # the ClimbMix data is stored tokenized with GPT-2 tokenizer
+    dataset_kwargs = {
+        "path": "nvidia/Nemotron-ClimbMix",
+        "split": "train",
+    }
+    output_dirname = "climbmix"
+    data_column_name = "tokens"
+    tokenizer = tiktoken.encoding_for_model("gpt-2")
+    upload_tag = "climbmix-400b-shuffle"
+
+else:
+    raise ValueError(f"Unknown dataset tag: {dataset_tag}")
+
 # Source dataset
-dataset_kwargs = {
-    "path": "HuggingFaceFW/fineweb-edu",
-    "split": "train",
-    "name": "sample-100BT", # ~100B GPT-2 tokens at ~3 chars/token => ~300B chars total
-}
 ds = load_dataset(**dataset_kwargs)
 
 # Shuffle to scramble the order
@@ -34,7 +69,7 @@ ndocs = len(ds) # total number of documents to process
 print(f"Total number of documents: {ndocs}")
 
 # Repackage into parquet files
-output_dir = "/home/ubuntu/.cache/nanochat/base_data"
+output_dir = f"/home/ubuntu/.cache/nanochat/base_data_{output_dirname}"
 os.makedirs(output_dir, exist_ok=True)
 
 # Write to parquet files
@@ -47,7 +82,8 @@ total_docs_processed = 0
 total_time_spent = 0
 t0 = time.time()
 for doc in ds:
-    text = doc['text']
+    data = doc[data_column_name]
+    text = tokenizer.decode(data) if tokenizer is not None else data
     shard_docs.append(text)
     shard_characters += len(text)
     collected_enough_chars = shard_characters >= chars_per_shard
@@ -79,14 +115,12 @@ for doc in ds:
         shard_index += 1
 
 # Demonstration of how the data was later uploaded to HuggingFace
-def upload():
-    import os
+if upload_to_hf:
     from huggingface_hub import HfApi
     token = os.getenv("HF_TOKEN")
     api = HfApi(token=token)
     api.upload_large_folder(
         folder_path=output_dir,
-        repo_id="karpathy/fineweb-edu-100b-shuffle",
+        repo_id=f"karpathy/{upload_tag}",
         repo_type="dataset",
     )
-# upload()