diff --git a/README.md b/README.md
index 99c4e26..a904e80 100644
--- a/README.md
+++ b/README.md
@@ -8,3 +8,6 @@ only suitable for single-threaded use (where they get some speedup over the gene
 
 Options -h HEADER -n NONCE are self explanatory.
 Add option -r RANGESIZE to search a range of nonces.
+
+Build the faster version courtesy of xenoncat's AVX2 4-way parallel blake2b assembly code with
+"make dev1" and bench with "time ./dev1 -n 255 -r 100"
diff --git a/dev_miner.h b/dev_miner.h
index 2fc720e..bdd3575 100644
--- a/dev_miner.h
+++ b/dev_miner.h
@@ -1,6 +1,9 @@
 // Equihash solver
 // Copyright (c) 2016 John Tromp
 
+// This development version uses xenoncat's highly optimized
+// 4-way parallel blake2b implementation
+
 // Fix N, K, such that n = N/(k+1) is integer
 // Fix M = 2^{n+1} hashes each of length N bits,
 // H_0, ... , H_{M-1}, generated fom (n+1)-bit indices.