diff --git a/3B2/3b2_cpu.c b/3B2/3b2_cpu.c
index 59d2abd2..3ec97b24 100644
--- a/3B2/3b2_cpu.c
+++ b/3B2/3b2_cpu.c
@@ -683,8 +683,11 @@ t_stat sys_boot(int32 flag, CONST char *ptr)
 {
     char gbuf[CBUFSIZE];
 
-    get_glyph(ptr, gbuf, 0);
+    if ((ptr = get_sim_sw(ptr)) == NULL) {
+        return SCPE_INVSW;
+    }
 
+    get_glyph(ptr, gbuf, 0);
     if (gbuf[0] && strcmp(gbuf, "CPU")) {
         return SCPE_ARG;
     }
diff --git a/3B2/tests/3b2_test.ini b/3B2/tests/3b2_test.ini
new file mode 100644
index 00000000..39f6a980
--- /dev/null
+++ b/3B2/tests/3b2_test.ini
@@ -0,0 +1,34 @@
+:: 3b2-diag.ini
+:: This script will run the available 3B2/400 core diagnostics.
+::
+cd %~p0
+set runlimit 2 minutes
+set on
+on error ignore
+on runtime echof "\r\n*** Test Runtime Limit %SIM_RUNLIMIT% %SIM_RUNLIMIT_UNITS% Exceeded ***\n"; exit 1
+
+set env DIAG_QUIET_MODE=0
+if ("%1" == "-v") set console notelnet
+else set -qu console telnet=localhost:65432,telnet=buffered; set env -a DIAG_QUIET_MODE=1
+
+:: Set maximum memory size
+set cpu 4M
+
+if not exist rev2_diags.dsk echof "\r\nMISSING - Diagnostic disk image '%~p0rev2_diags.dsk' is missing\n"; exit 1
+attach -rq ifloppy rev2_diags.dsk
+
+:: Initial setup
+expect "UTILITIES GUIDE" send "mcp\r"; go -q
+expect "Enter name of program to execute [  ]:" send "filledt\r"; go -q
+expect "Enter Load Device Option Number [0 (FD5)]:" send "0\r"; go -q
+expect "Enter name of program to execute [  ]:" send "dgmon\r"; go -q
+expect "Enter Load Device Option Number [0 (FD5)]:" send "0\r"; go -q
+expect "Did you boot filledt? [y or n] (n)" send "y\r"; go -q
+expect "DGMON > " send "DGN SBD\r"; go -q
+expect "SBD 0 (IN SLOT 0) DIAGNOSTICS PASSED" echof; echof "PASSED: 3B2 DGMON SBD Diagnostics."; exit 0
+expect [4] "FAIL" echof; echof "FAILED: 3B2 DGMON SBD Diagnostics."; exit 1
+
+::  Run tests
+if (DIAG_QUIET_MODE) echof "\nStarting 3B2 DGMON SBD Diagnostics."
+boot -q CPU
+return
diff --git a/3B2/tests/rev2_diags.dsk b/3B2/tests/rev2_diags.dsk
new file mode 100644
index 00000000..1fbfe909
Binary files /dev/null and b/3B2/tests/rev2_diags.dsk differ