diff --git a/xo-gc/include/xo/gc/X1CollectorConfig.hpp b/xo-gc/include/xo/gc/X1CollectorConfig.hpp
index 54296e2c..dec9545d 100644
--- a/xo-gc/include/xo/gc/X1CollectorConfig.hpp
+++ b/xo-gc/include/xo/gc/X1CollectorConfig.hpp
@@ -17,7 +17,12 @@ namespace xo {
             using size_type = std::size_t;
 
             /** copy of this config,
-             *  with @c arena_config_.size_ set to @p gen_z
+             *  but with @ref name_ set to @p name
+             **/
+            X1CollectorConfig with_name(std::string name);
+
+            /** copy of this config,
+             *  but with @c arena_config_.size_ set to @p gen_z
              **/
             X1CollectorConfig with_size(std::size_t gen_z);
 
diff --git a/xo-gc/src/gc/DX1Collector.cpp b/xo-gc/src/gc/DX1Collector.cpp
index a4375da5..ede4a734 100644
--- a/xo-gc/src/gc/DX1Collector.cpp
+++ b/xo-gc/src/gc/DX1Collector.cpp
@@ -25,6 +25,14 @@ namespace xo {
 
     namespace mm {
 
+        X1CollectorConfig
+        X1CollectorConfig::with_name(std::string name)
+        {
+            X1CollectorConfig copy = *this;
+            copy.name_ = std::move(name);
+            return copy;
+        }
+
         X1CollectorConfig
         X1CollectorConfig::with_size(std::size_t gen_z)
         {
@@ -33,20 +41,6 @@ namespace xo {
             return copy;
         }
 
-#ifdef NOT_USING
-        constexpr std::uint64_t
-        X1CollectorConfig::gen_mult() const {
-            return 1ul << arena_config_.header_size_bits_;
-        }
-#endif
-
-#ifdef NOT_USING
-        constexpr std::uint64_t
-        X1CollectorConfig::tseq_mult() const {
-            return 1ul << (gen_bits_ + arena_config_.header_size_bits_);
-        }
-#endif
-
         // ----- GCRunState -----
 
         GCRunState::GCRunState(generation gc_upto)