diff --git a/Machines/Acorn/Archimedes/Archimedes.cpp b/Machines/Acorn/Archimedes/Archimedes.cpp
index 9ad72fe10..d2aa5716a 100644
--- a/Machines/Acorn/Archimedes/Archimedes.cpp
+++ b/Machines/Acorn/Archimedes/Archimedes.cpp
@@ -750,13 +750,13 @@ class ConcreteMachine:
 
 					all.insert(instruction);
 
-//					if(executor_.pc() == 0x03801404) {
-//						printf("");
-//					}
-//					log |= (executor_.pc() > 0 && executor_.pc() < 0x03800000);
-//					log |= executor_.pc() == 0x02000078;
+					if(executor_.pc() == 0x03801a0c) {
+						printf("");
+					}
+//					log |= (executor_.pc() > 0x02000000 && executor_.pc() < 0x02000078);
+					log |= executor_.pc() == 0x03801980;
 //					log |= (executor_.pc() > 0x03801000);
-//					log &= (executor_.pc() != 0x038019f8);
+					log &= executor_.pc() != 0x03801a0c;
 
 					if(executor_.pc() == 0x02000078) {
 						if(!all.empty()) {
@@ -783,6 +783,8 @@ class ConcreteMachine:
 
 //					if(
 //						executor_.pc() > 0x038021d0 &&
+//							last_r1 != executor_.registers()[1]
+//							 ||
 //						(
 //							last_link != executor_.registers()[14] ||
 //							last_r0 != executor_.registers()[0] ||
@@ -797,6 +799,10 @@ class ConcreteMachine:
 //							executor_.registers()[10],
 //							executor_.registers()[1]
 //						);
+//						logger.info().append("%08x modified R1 to %08x",
+//							last_pc,
+//							executor_.registers()[1]
+//						);
 //						last_link = executor_.registers()[14];
 //						last_r0 = executor_.registers()[0];
 //						last_r10 = executor_.registers()[10];
diff --git a/Machines/Utility/ROMCatalogue.cpp b/Machines/Utility/ROMCatalogue.cpp
index 410ac798c..dfc9f9827 100644
--- a/Machines/Utility/ROMCatalogue.cpp
+++ b/Machines/Utility/ROMCatalogue.cpp
@@ -540,6 +540,9 @@ Description::Description(Name name) {
 			*this = Description(name, "Electron", "the Electron MOS ROM v1.00", "os.rom", 16*1024, 0xbf63fb1fu);
 		break;
 
+		case Name::AcornRISCOS311:
+			*this = Description(name, "Archimedes", "RISC OS v3.11", "ROM311", 2*1024*1024, 0x54c0c963u);
+		break;
 		case Name::AcornRISCOS319:
 			*this = Description(name, "Archimedes", "RISC OS v3.19", "ROM319", 2*1024*1024, 0x00c7a3d3u);
 		break;
diff --git a/Machines/Utility/ROMCatalogue.hpp b/Machines/Utility/ROMCatalogue.hpp
index a672e9522..51f3d8b72 100644
--- a/Machines/Utility/ROMCatalogue.hpp
+++ b/Machines/Utility/ROMCatalogue.hpp
@@ -32,6 +32,7 @@ enum Name {
 	Acorn1770DFS,
 
 	// Acorn Archimedes.
+	AcornRISCOS311,
 	AcornRISCOS319,
 
 	// Amiga.