diff --git a/libraries/Ethernet/src/Ethernet.cpp b/libraries/Ethernet/src/Ethernet.cpp
index 0f9effb1a..3eea69a2a 100644
--- a/libraries/Ethernet/src/Ethernet.cpp
+++ b/libraries/Ethernet/src/Ethernet.cpp
@@ -16,8 +16,10 @@ int EthernetClass::begin(uint8_t *mac_address)
 
   // Initialise the basic info
   W5100.init();
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.setMACAddress(mac_address);
   W5100.setIPAddress(IPAddress(0,0,0,0).raw_address());
+  SPI.endTransaction();
 
   // Now try to get our config info from a DHCP server
   int ret = _dhcp->beginWithDHCP(mac_address);
@@ -25,9 +27,11 @@ int EthernetClass::begin(uint8_t *mac_address)
   {
     // We've successfully found a DHCP server and got our configuration info, so set things
     // accordingly
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
     W5100.setIPAddress(_dhcp->getLocalIp().raw_address());
     W5100.setGatewayIp(_dhcp->getGatewayIp().raw_address());
     W5100.setSubnetMask(_dhcp->getSubnetMask().raw_address());
+    SPI.endTransaction();
     _dnsServerAddress = _dhcp->getDnsServerIp();
   }
 
@@ -61,10 +65,12 @@ void EthernetClass::begin(uint8_t *mac_address, IPAddress local_ip, IPAddress dn
 void EthernetClass::begin(uint8_t *mac, IPAddress local_ip, IPAddress dns_server, IPAddress gateway, IPAddress subnet)
 {
   W5100.init();
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.setMACAddress(mac);
   W5100.setIPAddress(local_ip.raw_address());
   W5100.setGatewayIp(gateway.raw_address());
   W5100.setSubnetMask(subnet.raw_address());
+  SPI.endTransaction();
   _dnsServerAddress = dns_server;
 }
 
@@ -80,9 +86,11 @@ int EthernetClass::maintain(){
       case DHCP_CHECK_RENEW_OK:
       case DHCP_CHECK_REBIND_OK:
         //we might have got a new IP.
+        SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
         W5100.setIPAddress(_dhcp->getLocalIp().raw_address());
         W5100.setGatewayIp(_dhcp->getGatewayIp().raw_address());
         W5100.setSubnetMask(_dhcp->getSubnetMask().raw_address());
+        SPI.endTransaction();
         _dnsServerAddress = _dhcp->getDnsServerIp();
         break;
       default:
@@ -96,21 +104,27 @@ int EthernetClass::maintain(){
 IPAddress EthernetClass::localIP()
 {
   IPAddress ret;
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.getIPAddress(ret.raw_address());
+  SPI.endTransaction();
   return ret;
 }
 
 IPAddress EthernetClass::subnetMask()
 {
   IPAddress ret;
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.getSubnetMask(ret.raw_address());
+  SPI.endTransaction();
   return ret;
 }
 
 IPAddress EthernetClass::gatewayIP()
 {
   IPAddress ret;
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.getGatewayIp(ret.raw_address());
+  SPI.endTransaction();
   return ret;
 }
 
diff --git a/libraries/Ethernet/src/utility/socket.cpp b/libraries/Ethernet/src/utility/socket.cpp
index ff2ec3d78..4ed4317ea 100644
--- a/libraries/Ethernet/src/utility/socket.cpp
+++ b/libraries/Ethernet/src/utility/socket.cpp
@@ -12,6 +12,7 @@ uint8_t socket(SOCKET s, uint8_t protocol, uint16_t port, uint8_t flag)
   if ((protocol == SnMR::TCP) || (protocol == SnMR::UDP) || (protocol == SnMR::IPRAW) || (protocol == SnMR::MACRAW) || (protocol == SnMR::PPPOE))
   {
     close(s);
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
     W5100.writeSnMR(s, protocol | flag);
     if (port != 0) {
       W5100.writeSnPORT(s, port);
@@ -22,7 +23,7 @@ uint8_t socket(SOCKET s, uint8_t protocol, uint16_t port, uint8_t flag)
     }
 
     W5100.execCmdSn(s, Sock_OPEN);
-    
+    SPI.endTransaction();
     return 1;
   }
 
@@ -32,7 +33,10 @@ uint8_t socket(SOCKET s, uint8_t protocol, uint16_t port, uint8_t flag)
 
 uint8_t socketStatus(SOCKET s)
 {
-  return W5100.readSnSR(s);
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
+  uint8_t status = W5100.readSnSR(s);
+  SPI.endTransaction();
+  return status;
 }
 
 
@@ -41,8 +45,10 @@ uint8_t socketStatus(SOCKET s)
  */
 void close(SOCKET s)
 {
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.execCmdSn(s, Sock_CLOSE);
   W5100.writeSnIR(s, 0xFF);
+  SPI.endTransaction();
 }
 
 
@@ -52,9 +58,13 @@ void close(SOCKET s)
  */
 uint8_t listen(SOCKET s)
 {
-  if (W5100.readSnSR(s) != SnSR::INIT)
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
+  if (W5100.readSnSR(s) != SnSR::INIT) {
+    SPI.endTransaction();
     return 0;
+  }
   W5100.execCmdSn(s, Sock_LISTEN);
+  SPI.endTransaction();
   return 1;
 }
 
@@ -76,9 +86,11 @@ uint8_t connect(SOCKET s, uint8_t * addr, uint16_t port)
     return 0;
 
   // set destination IP
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.writeSnDIPR(s, addr);
   W5100.writeSnDPORT(s, port);
   W5100.execCmdSn(s, Sock_CONNECT);
+  SPI.endTransaction();
 
   return 1;
 }
@@ -91,7 +103,9 @@ uint8_t connect(SOCKET s, uint8_t * addr, uint16_t port)
  */
 void disconnect(SOCKET s)
 {
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.execCmdSn(s, Sock_DISCON);
+  SPI.endTransaction();
 }
 
 
@@ -113,17 +127,21 @@ uint16_t send(SOCKET s, const uint8_t * buf, uint16_t len)
   // if freebuf is available, start.
   do 
   {
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
     freesize = W5100.getTXFreeSize(s);
     status = W5100.readSnSR(s);
+    SPI.endTransaction();
     if ((status != SnSR::ESTABLISHED) && (status != SnSR::CLOSE_WAIT))
     {
       ret = 0; 
       break;
     }
+    yield();
   } 
   while (freesize < ret);
 
   // copy data
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.send_data_processing(s, (uint8_t *)buf, ret);
   W5100.execCmdSn(s, Sock_SEND);
 
@@ -133,12 +151,17 @@ uint16_t send(SOCKET s, const uint8_t * buf, uint16_t len)
     /* m2008.01 [bj] : reduce code */
     if ( W5100.readSnSR(s) == SnSR::CLOSED )
     {
+      SPI.endTransaction();
       close(s);
       return 0;
     }
+    SPI.endTransaction();
+    yield();
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   }
   /* +2008.01 bj */
   W5100.writeSnIR(s, SnIR::SEND_OK);
+  SPI.endTransaction();
   return ret;
 }
 
@@ -152,6 +175,7 @@ uint16_t send(SOCKET s, const uint8_t * buf, uint16_t len)
 int16_t recv(SOCKET s, uint8_t *buf, int16_t len)
 {
   // Check how much data is available
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   int16_t ret = W5100.getRXReceivedSize(s);
   if ( ret == 0 )
   {
@@ -178,13 +202,17 @@ int16_t recv(SOCKET s, uint8_t *buf, int16_t len)
     W5100.recv_data_processing(s, buf, ret);
     W5100.execCmdSn(s, Sock_RECV);
   }
+  SPI.endTransaction();
   return ret;
 }
 
 
 int16_t recvAvailable(SOCKET s)
 {
-  return W5100.getRXReceivedSize(s);
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
+  int16_t ret = W5100.getRXReceivedSize(s);
+  SPI.endTransaction();
+  return ret;
 }
 
 
@@ -195,8 +223,9 @@ int16_t recvAvailable(SOCKET s)
  */
 uint16_t peek(SOCKET s, uint8_t *buf)
 {
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.recv_data_processing(s, buf, 1, 1);
-
+  SPI.endTransaction();
   return 1;
 }
 
@@ -225,6 +254,7 @@ uint16_t sendto(SOCKET s, const uint8_t *buf, uint16_t len, uint8_t *addr, uint1
   }
   else
   {
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
     W5100.writeSnDIPR(s, addr);
     W5100.writeSnDPORT(s, port);
 
@@ -239,12 +269,17 @@ uint16_t sendto(SOCKET s, const uint8_t *buf, uint16_t len, uint8_t *addr, uint1
       {
         /* +2008.01 [bj]: clear interrupt */
         W5100.writeSnIR(s, (SnIR::SEND_OK | SnIR::TIMEOUT)); /* clear SEND_OK & TIMEOUT */
+        SPI.endTransaction();
         return 0;
       }
+      SPI.endTransaction();
+      yield();
+      SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
     }
 
     /* +2008.01 bj */
     W5100.writeSnIR(s, SnIR::SEND_OK);
+    SPI.endTransaction();
   }
   return ret;
 }
@@ -264,6 +299,7 @@ uint16_t recvfrom(SOCKET s, uint8_t *buf, uint16_t len, uint8_t *addr, uint16_t
 
   if ( len > 0 )
   {
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
     ptr = W5100.readSnRX_RD(s);
     switch (W5100.readSnMR(s) & 0x07)
     {
@@ -318,6 +354,7 @@ uint16_t recvfrom(SOCKET s, uint8_t *buf, uint16_t len, uint8_t *addr, uint16_t
       break;
     }
     W5100.execCmdSn(s, Sock_RECV);
+    SPI.endTransaction();
   }
   return data_len;
 }
@@ -341,6 +378,7 @@ uint16_t igmpsend(SOCKET s, const uint8_t * buf, uint16_t len)
   if (ret == 0)
     return 0;
 
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.send_data_processing(s, (uint8_t *)buf, ret);
   W5100.execCmdSn(s, Sock_SEND);
 
@@ -350,18 +388,24 @@ uint16_t igmpsend(SOCKET s, const uint8_t * buf, uint16_t len)
     {
       /* in case of igmp, if send fails, then socket closed */
       /* if you want change, remove this code. */
+      SPI.endTransaction();
       close(s);
       return 0;
     }
+    SPI.endTransaction();
+    yield();
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   }
 
   W5100.writeSnIR(s, SnIR::SEND_OK);
+  SPI.endTransaction();
   return ret;
 }
 
 uint16_t bufferData(SOCKET s, uint16_t offset, const uint8_t* buf, uint16_t len)
 {
   uint16_t ret =0;
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   if (len > W5100.getTXFreeSize(s))
   {
     ret = W5100.getTXFreeSize(s); // check size not to exceed MAX size.
@@ -371,6 +415,7 @@ uint16_t bufferData(SOCKET s, uint16_t offset, const uint8_t* buf, uint16_t len)
     ret = len;
   }
   W5100.send_data_processing_offset(s, offset, buf, ret);
+  SPI.endTransaction();
   return ret;
 }
 
@@ -386,14 +431,17 @@ int startUDP(SOCKET s, uint8_t* addr, uint16_t port)
   }
   else
   {
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
     W5100.writeSnDIPR(s, addr);
     W5100.writeSnDPORT(s, port);
+    SPI.endTransaction();
     return 1;
   }
 }
 
 int sendUDP(SOCKET s)
 {
+  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   W5100.execCmdSn(s, Sock_SEND);
 		
   /* +2008.01 bj */
@@ -403,12 +451,17 @@ int sendUDP(SOCKET s)
     {
       /* +2008.01 [bj]: clear interrupt */
       W5100.writeSnIR(s, (SnIR::SEND_OK|SnIR::TIMEOUT));
+      SPI.endTransaction();
       return 0;
     }
+    SPI.endTransaction();
+    yield();
+    SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
   }
 
   /* +2008.01 bj */	
   W5100.writeSnIR(s, SnIR::SEND_OK);
+  SPI.endTransaction();
 
   /* Sent ok */
   return 1;
diff --git a/libraries/Ethernet/src/utility/w5100.cpp b/libraries/Ethernet/src/utility/w5100.cpp
index 7e8b6348a..a70107344 100644
--- a/libraries/Ethernet/src/utility/w5100.cpp
+++ b/libraries/Ethernet/src/utility/w5100.cpp
@@ -15,8 +15,6 @@
 // W5100 controller instance
 W5100Class W5100;
 
-#define SPI_CS 10
-
 #define TX_RX_MAX_BUF_SIZE 2048
 #define TX_BUF 0x1100
 #define RX_BUF (TX_BUF + TX_RX_MAX_BUF_SIZE)
diff --git a/libraries/Ethernet/src/utility/w5100.h b/libraries/Ethernet/src/utility/w5100.h
index 3b5a69336..ba72e2181 100644
--- a/libraries/Ethernet/src/utility/w5100.h
+++ b/libraries/Ethernet/src/utility/w5100.h
@@ -12,6 +12,14 @@
 
 #include <SPI.h>
 
+#define SPI_CS 10
+
+#if defined(ARDUINO_ARCH_AVR)
+#define SPI_ETHERNET_SETTINGS SPISettings(4000000, MSBFIRST, SPI_MODE0)
+#else
+#define SPI_ETHERNET_SETTINGS SPI_CS,SPISettings(4000000, MSBFIRST, SPI_MODE0)
+#endif
+
 #define MAX_SOCK_NUM 4
 
 typedef uint8_t SOCKET;