diff --git a/simulator/sim_lib/exchange_packet.h b/simulator/sim_lib/exchange_packet.h
index b7d712b..d3416a8 100644
--- a/simulator/sim_lib/exchange_packet.h
+++ b/simulator/sim_lib/exchange_packet.h
@@ -416,6 +416,7 @@ public:
 	CREATE_FIELD(CAddr_t,                 YmpReadAddress,        2,        0,      7,     0)
 	CREATE_FIELD(uint8_t,             YmpExchangeAddress,        5,        8,     15,     0)
 	CREATE_FIELD(uint8_t,                YmpVectorLength,        5,       16,     22,     0)
+//	Here the number of bits is actually series dependent. YEL for example has 4 bits, J90 has 6. Leaving as 8 for now as it doesn't seem to cause trouble.
 	CREATE_FIELD(uint8_t,               YmpClusterNumber,        5,       24,     31,     0)
 	CREATE_FIELD(uint8_t,               YmpVectorNotUsed,        6,        0,      0,     0)
 	CREATE_FIELD(uint8_t,               YmpProcessorType,        7,        0,      1,     0)
diff --git a/simulator/sim_lib/sim_iop_periph.cpp b/simulator/sim_lib/sim_iop_periph.cpp
index 8d8e996..50cc684 100644
--- a/simulator/sim_lib/sim_iop_periph.cpp
+++ b/simulator/sim_lib/sim_iop_periph.cpp
@@ -256,6 +256,7 @@ void SimIopPeripheral_c::HandlePacket(std::vector<CInt_t> &aPacket, bool aIosESt
 		case FunctionCodes_e::RD:
 		case FunctionCodes_e::RDHLD:
 		case FunctionCodes_e::RDRD: {
+			int BufferCnt = (Function == FunctionCodes_e::RDRD) ? 2 : 1;
 			uint32_t Addr[2];
 			uint32_t DataLen[2];
 			uint32_t TransferLen[2];
@@ -272,10 +273,10 @@ void SimIopPeripheral_c::HandlePacket(std::vector<CInt_t> &aPacket, bool aIosESt
 			case ChannelNumbers_e::Disk:
 				break;
 			case ChannelNumbers_e::Tape:
-				Read(Addr, DataLen, TransferLen, 2, mTapeFile);
+				Read(Addr, DataLen, TransferLen, BufferCnt, mTapeFile);
 				break;
 			case ChannelNumbers_e::File:
-				Read(Addr, DataLen, TransferLen, 2, mFile);
+				Read(Addr, DataLen, TransferLen, BufferCnt, mFile);
 				break;
 			default:
 				CRAY_ASSERT(false);
@@ -290,6 +291,7 @@ void SimIopPeripheral_c::HandlePacket(std::vector<CInt_t> &aPacket, bool aIosESt
 		case FunctionCodes_e::WR:
 		case FunctionCodes_e::WRHLD:
 		case FunctionCodes_e::WRWR: {
+			int BufferCnt = (Function == FunctionCodes_e::RDRD) ? 2 : 1;
 			uint32_t Addr[2];
 			uint32_t DataLen[2];
 			uint32_t TransferLen[2];
@@ -301,15 +303,15 @@ void SimIopPeripheral_c::HandlePacket(std::vector<CInt_t> &aPacket, bool aIosESt
 			TransferLen[1] = uint32_t(GetBits(aPacket[4], TransferLenReq2Range));
 			switch (ChannelNumber) {
 				case ChannelNumbers_e::Printer:
-					Write(Addr, DataLen, TransferLen, 2, mPrinterFile);
+					Write(Addr, DataLen, TransferLen, BufferCnt, mPrinterFile);
 				break;
 				case ChannelNumbers_e::Disk:
 				break;
 				case ChannelNumbers_e::Tape:
-					Write(Addr, DataLen, TransferLen, 2, mTapeFile);
+					Write(Addr, DataLen, TransferLen, BufferCnt, mTapeFile);
 				break;
 				case ChannelNumbers_e::File:
-					Write(Addr, DataLen, TransferLen, 2, mFile);
+					Write(Addr, DataLen, TransferLen, BufferCnt, mFile);
 				break;
 				default:
 					CRAY_ASSERT(false);