diff --git a/build/misc.tcl b/build/misc.tcl
index 54a78c31..72af4e23 100644
--- a/build/misc.tcl
+++ b/build/misc.tcl
@@ -1690,9 +1690,12 @@ respond "*" ":pcnvrt .temp.; ioelev bin\r"
 expect ":KILL"
 move_to_klfe ".temp.; ioelev a11"
 
-# The KL10 "MX-DL" IOELEV won't assemble due to CHADD being undefined.
-# Maybe roll back to IOELEV 431, or fix it in new version 433.  Maybe
-# link with 11DDT 16K.
+# The KL10 "MX-DL" IOELEV.  Put in same directory as KLRUG BIN.
+# TS BOOT11 stuffs it over DL10 in timesharing.  TS 11BOOT makes a
+# @ BOOT11 to stuff out of timesharing.
+respond "*" ":palx sysbin;_system;ioelev\r"
+respond "MACHINE NAME =" "MX\r"
+expect ":KILL"
 
 # MINITS
 respond "*" ":cwd mits.s\r"
diff --git a/src/system/ioelev.432 b/src/system/ioelev.433
similarity index 99%
rename from src/system/ioelev.432
rename to src/system/ioelev.433
index b5e4dc81..179a008c 100755
--- a/src/system/ioelev.432
+++ b/src/system/ioelev.433
@@ -96,6 +96,7 @@ CHSBTB=0	;CHAOSNET INTERFACE IS NEW, DOESN'T GET HUNG ANY MORE
 CHAD0==440	;CHAOSNET ADDRESS OF THIS PDP11 ITSELF
 DLCADR==1440	;CHAOSNET ADDRESS OF PDP10 CONNECTED VIA DL10 (MX)
 CHAD1==3040	;SECOND INTERFACE
+CHADD==440	;The DOVER protocol translator only works for this address
 TEN11P==0	;NO TEN-11 INTERFACE
 ETHERP==0	;NO ETHERNET
 FTPULS==0	;INITIALLY, MX DOES NOT GENERATE TEST PACKETS