diff --git a/devices/ioctrl/amic.cpp b/devices/ioctrl/amic.cpp
index bc7dd9b..fc4ed81 100644
--- a/devices/ioctrl/amic.cpp
+++ b/devices/ioctrl/amic.cpp
@@ -105,7 +105,7 @@ uint32_t AMIC::read(uint32_t reg_start, uint32_t offset, int size)
     case 1:
         return this->viacuda->read(offset >> 9);
     case 4: // SCC registers
-        return this->escc->read((offset >> 1) & 0xF);
+        return this->escc->read(compat_to_macrisc[(offset >> 1) & 0xF]);
     case 0xA: // MACE registers
         return this->mace->read((offset >> 4) & 0x1F);
     case 0x10: // SCSI registers
@@ -185,7 +185,7 @@ void AMIC::write(uint32_t reg_start, uint32_t offset, uint32_t value, int size)
         this->viacuda->write(offset >> 9, value);
         return;
     case 4:
-        this->escc->write((offset >> 1) & 0xF, value);
+        this->escc->write(compat_to_macrisc[(offset >> 1) & 0xF], value);
         return;
     case 0xA: // MACE registers
         this->mace->write((offset >> 4) & 0x1F, value);
diff --git a/devices/ioctrl/grandcentral.cpp b/devices/ioctrl/grandcentral.cpp
index 84a44b3..b8782ad 100644
--- a/devices/ioctrl/grandcentral.cpp
+++ b/devices/ioctrl/grandcentral.cpp
@@ -95,7 +95,7 @@ uint32_t GrandCentral::read(uint32_t reg_start, uint32_t offset, int size)
             return this->mace->read((offset >> 4) & 0x1F);
         case 2: // ESCC compatible addressing
             if ((offset & 0xFF) < 16) {
-                return this->escc->read((offset >> 1) & 0xF);
+                return this->escc->read(compat_to_macrisc[(offset >> 1) & 0xF]);
             }
             // fallthrough
         case 3: // ESCC MacRISC addressing
@@ -152,7 +152,7 @@ void GrandCentral::write(uint32_t reg_start, uint32_t offset, uint32_t value, in
             break;
         case 2: // ESCC compatible addressing
             if ((offset & 0xFF) < 16) {
-                this->escc->write((offset >> 1) & 0xF, value);
+                this->escc->write(compat_to_macrisc[(offset >> 1) & 0xF], value);
                 break;
             }
             // fallthrough
diff --git a/devices/ioctrl/heathrow.cpp b/devices/ioctrl/heathrow.cpp
index 58aae8f..f366ed8 100644
--- a/devices/ioctrl/heathrow.cpp
+++ b/devices/ioctrl/heathrow.cpp
@@ -138,7 +138,7 @@ uint32_t HeathrowIC::read(uint32_t reg_start, uint32_t offset, int size) {
         break;
     case 0x12: // ESCC compatible addressing
         if ((offset & 0xFF) < 16) {
-            return this->escc->read((offset >> 1) & 0xF);
+            return this->escc->read(compat_to_macrisc[(offset >> 1) & 0xF]);
         }
         // fallthrough
     case 0x13: // ESCC MacRISC addressing
@@ -180,7 +180,7 @@ void HeathrowIC::write(uint32_t reg_start, uint32_t offset, uint32_t value, int
         break;
     case 0x12: // ESCC compatible addressing
         if ((offset & 0xFF) < 16) {
-            this->escc->write((offset >> 1) & 0xF, value);
+            this->escc->write(compat_to_macrisc[(offset >> 1) & 0xF], value);
             break;
         }
         // fallthrough
diff --git a/devices/serial/escc.cpp b/devices/serial/escc.cpp
index e1a9b8c..a801df5 100644
--- a/devices/serial/escc.cpp
+++ b/devices/serial/escc.cpp
@@ -27,6 +27,13 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #include <cinttypes>
 #include <memory>
 
+/** Remap the compatible addressing scheme to MacRISC one. */
+const uint8_t compat_to_macrisc[6] = {
+    EsccReg::Port_B_Cmd,    EsccReg::Port_A_Cmd,
+    EsccReg::Port_B_Data,   EsccReg::Port_A_Data,
+    EsccReg::Enh_Reg_B,     EsccReg::Enh_Reg_A
+};
+
 EsccController::EsccController()
 {
     this->ch_a = std::unique_ptr<EsccChannel> (new EsccChannel("A"));
diff --git a/devices/serial/escc.h b/devices/serial/escc.h
index e7194ab..99db9eb 100644
--- a/devices/serial/escc.h
+++ b/devices/serial/escc.h
@@ -1,6 +1,6 @@
 /*
 DingusPPC - The Experimental PowerPC Macintosh emulator
-Copyright (C) 2018-21 divingkatae and maximum
+Copyright (C) 2018-22 divingkatae and maximum
                       (theweirdo)     spatium
 
 (Contact divingkatae#1017 or powermax#2286 on Discord for more info)
@@ -30,18 +30,26 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 /** ESCC register positions */
 /* Please note that the registers below are provided
-   by Apple I/O controllers for accessing ESCC in a
-   more convenient way. Actual physical addresses
-   are controller dependent. */
+   by the Apple I/O controllers for accessing ESCC
+   in a more convenient way. Actual physical addresses
+   are controller dependent.
+   The registers are ordered according with the MacRISC
+   scheme used in the PCI Power Macintosh models.
+   Pre-PCI Macs uses the so-called compatibility
+   addressing. Please use compat_to_macrisc table
+   below for converting from compat to MacRISC.
+ */
 enum EsccReg : uint8_t {
     Port_B_Cmd      = 0,
-    Port_A_Cmd      = 1,
-    Port_B_Data     = 2, // direct access to WR8/RR8
+    Port_B_Data     = 1, // direct access to WR8/RR8
+    Port_A_Cmd      = 2,
     Port_A_Data     = 3, // direct access to WR8/RR8
     Enh_Reg_B       = 4, // undocumented Apple extension
     Enh_Reg_A       = 5, // undocumented Apple extension
 };
 
+extern const uint8_t compat_to_macrisc[6];
+
 /** LocalTalk LTPC registers provided by a MacIO controller. */
 enum LocalTalkReg : uint8_t {
     Rec_Count   = 8,