diff --git a/sim/imperas.ic b/sim/imperas.ic
index bd6f92cea..1382f4d63 100644
--- a/sim/imperas.ic
+++ b/sim/imperas.ic
@@ -51,9 +51,13 @@
 --override cpu/unaligned=T  # Zicclsm (should be true)
 --override cpu/ignore_non_leaf_DAU=1
 --override cpu/wfi_is_nop=T
---override cpu/misa_Extensions_mask=0x0
+--override cpu/misa_Extensions_mask=0x0 # MISA not writable
 --override cpu/Sstc=T
 
+# unsuccessfully attempt to add B extension (DH 12/21/23)
+#--override cpu/add_Extensions="B"
+#--override cpu/misa_Extensions=0x0014112F
+
 # Enable SVADU hardware update of A/D bits when menvcfg.ADUE=1
 --override cpu/Svadu=T
 #--override cpu/updatePTEA=F