diff --git a/MdePkg/Include/AArch64/ProcessorBind.h b/MdePkg/Include/AArch64/ProcessorBind.h
index 968c18f915..f4a544b34d 100644
--- a/MdePkg/Include/AArch64/ProcessorBind.h
+++ b/MdePkg/Include/AArch64/ProcessorBind.h
@@ -142,6 +142,11 @@ typedef INT64   INTN;
 ///
 #define MAX_ADDRESS   0xFFFFFFFFFFFFFFFFULL
 
+///
+/// Maximum usable address at boot time (48 bits using 4 KB pages)
+///
+#define MAX_ALLOC_ADDRESS   0xFFFFFFFFFFFFULL
+
 ///
 /// Maximum legal AArch64 INTN and UINTN values.
 ///
diff --git a/MdePkg/Include/Arm/ProcessorBind.h b/MdePkg/Include/Arm/ProcessorBind.h
index 8cca0f3bb0..16a61fc7a3 100644
--- a/MdePkg/Include/Arm/ProcessorBind.h
+++ b/MdePkg/Include/Arm/ProcessorBind.h
@@ -148,6 +148,11 @@ typedef INT32   INTN;
 ///
 #define MAX_ADDRESS  0xFFFFFFFF
 
+///
+/// Maximum usable address at boot time
+///
+#define MAX_ALLOC_ADDRESS   MAX_ALLOC_ADDRESS
+
 ///
 /// Maximum legal ARM INTN and UINTN values.
 ///
diff --git a/MdePkg/Include/Ebc/ProcessorBind.h b/MdePkg/Include/Ebc/ProcessorBind.h
index 5217cfd97e..45beb75728 100644
--- a/MdePkg/Include/Ebc/ProcessorBind.h
+++ b/MdePkg/Include/Ebc/ProcessorBind.h
@@ -103,6 +103,11 @@ typedef unsigned long         UINTN;
 ///
 #define MAX_ADDRESS   ((UINTN)(~0ULL >> (64 - sizeof (INTN) * 8)))
 
+///
+/// Maximum usable address at boot time (48 bits using 4 KB pages)
+///
+#define MAX_ALLOC_ADDRESS   MAX_ADDRESS
+
 ///
 /// Maximum legal EBC INTN and UINTN values.
 ///
diff --git a/MdePkg/Include/Ia32/ProcessorBind.h b/MdePkg/Include/Ia32/ProcessorBind.h
index 8e4de7029c..71d53e2543 100644
--- a/MdePkg/Include/Ia32/ProcessorBind.h
+++ b/MdePkg/Include/Ia32/ProcessorBind.h
@@ -246,6 +246,11 @@ typedef INT32   INTN;
 ///
 #define MAX_ADDRESS   0xFFFFFFFF
 
+///
+/// Maximum usable address at boot time
+///
+#define MAX_ALLOC_ADDRESS   MAX_ADDRESS
+
 ///
 /// Maximum legal IA-32 INTN and UINTN values.
 ///
diff --git a/MdePkg/Include/X64/ProcessorBind.h b/MdePkg/Include/X64/ProcessorBind.h
index e425428587..1c04090c7d 100644
--- a/MdePkg/Include/X64/ProcessorBind.h
+++ b/MdePkg/Include/X64/ProcessorBind.h
@@ -260,6 +260,11 @@ typedef INT64   INTN;
 ///
 #define MAX_ADDRESS   0xFFFFFFFFFFFFFFFFULL
 
+///
+/// Maximum usable address at boot time
+///
+#define MAX_ALLOC_ADDRESS   MAX_ADDRESS
+
 ///
 /// Maximum legal x64 INTN and UINTN values.
 ///