diff --git a/config/rv32gc/imperas.ic b/config/rv32gc/imperas.ic
index fe4a3dbed..9e9eef55f 100644
--- a/config/rv32gc/imperas.ic
+++ b/config/rv32gc/imperas.ic
@@ -59,6 +59,24 @@
 #--override cpu/instret_undefined=T
 #--override cpu/hpmcounter_undefined=T
 
+# context registers not implemented
+--override cpu/scontext_undefined=T
+--override cpu/mcontext_undefined=T
+
+# nonratified mnosie register not implemented
+--override cpu/mnoise_undefined=T
+
+# mcause and scause only have 4 lsbs of code and 1 msb of interrupt flag
+#--override cpu/ecode_mask=0x8000000F  # for RV32
+--override cpu/ecode_mask=0x800000000000000F # for RV64
+
+# Debug mode not yet supported
+--override cpu/debug_mode=none
+
+# Zkr entropy source and seed register not supported.
+--override cpu/Zkr=F
+
+
 --override cpu/reset_address=0x80000000
 
 --override cpu/unaligned=F  # Zicclsm (should be true)
diff --git a/config/rv64gc/imperas.ic b/config/rv64gc/imperas.ic
index 1b038c920..31584d22d 100644
--- a/config/rv64gc/imperas.ic
+++ b/config/rv64gc/imperas.ic
@@ -57,15 +57,23 @@
 #--override cpu/instret_undefined=T
 #--override cpu/hpmcounter_undefined=T
 
+# context registers not implemented
 --override cpu/scontext_undefined=T
 --override cpu/mcontext_undefined=T
+
+# nonratified mnosie register not implemented
 --override cpu/mnoise_undefined=T
-# *** how to override other undefined registers: seed, mphmevent, mseccfg, debugger registers
-#--override cpu/seed_undefined=T
-#--override mhpmevent3_undefined=T
-#--override cpu/mseccfg_undefined=T
-#--override cpu/tselect_undefined=T
-#--override cpu/tdata1_undefined=T
+
+# mcause and scause only have 4 lsbs of code and 1 msb of interrupt flag
+#--override cpu/ecode_mask=0x8000000F  # for RV32
+--override cpu/ecode_mask=0x800000000000000F # for RV64
+
+# Debug mode not yet supported
+--override cpu/debug_mode=none
+
+# Zkr entropy source and seed register not supported.
+--override cpu/Zkr=F
+
 
 
 --override cpu/reset_address=0x80000000