diff --git a/3B2/3b2_cpu.c b/3B2/3b2_cpu.c
index dc9f1e5b..6ccab7da 100644
--- a/3B2/3b2_cpu.c
+++ b/3B2/3b2_cpu.c
@@ -367,6 +367,8 @@ MTAB cpu_mod[] = {
       &cpu_set_size, NULL, NULL, "Set Memory to 4M bytes" },
 #endif
 #if defined(REV3)
+    { UNIT_MSIZE, (1u << 22), NULL, "4M",
+      &cpu_set_size, NULL, NULL, "Set Memory to 4M bytes" },
     { UNIT_MSIZE, (1u << 23), NULL, "8M",
       &cpu_set_size, NULL, NULL, "Set Memory to 8M bytes" },
     { UNIT_MSIZE, (1u << 24), NULL, "16M",
diff --git a/3B2/3b2_stddev.c b/3B2/3b2_stddev.c
index aa47c344..039dcced 100644
--- a/3B2/3b2_stddev.c
+++ b/3B2/3b2_stddev.c
@@ -741,6 +741,12 @@ DEVICE flt_dev = {
  */
 static uint32 mem_size(uint8 slot) {
     switch(MEM_SIZE) {
+    case MSIZ_4M:
+        if (slot == 0) {
+            return MEM_EQP|MEM_4M;
+        } else {
+            return 0;
+        }
     case MSIZ_8M:
         if (slot <= 1) {
             return MEM_EQP|MEM_4M;