diff --git a/Marlin/src/core/macros.h b/Marlin/src/core/macros.h
index a0ccebc078..dcc688ae29 100644
--- a/Marlin/src/core/macros.h
+++ b/Marlin/src/core/macros.h
@@ -53,6 +53,7 @@
 
 #define _FORCE_INLINE_ __attribute__((__always_inline__)) __inline__
 #define  FORCE_INLINE  __attribute__((always_inline)) inline
+#define NO_INLINE      __attribute__((noinline))
 #define _UNUSED      __attribute__((unused))
 #define _O0          __attribute__((optimize("O0")))
 #define _Os          __attribute__((optimize("Os")))
diff --git a/Marlin/src/core/serial_base.h b/Marlin/src/core/serial_base.h
index b60e3b5788..220ccae831 100644
--- a/Marlin/src/core/serial_base.h
+++ b/Marlin/src/core/serial_base.h
@@ -78,23 +78,23 @@ struct SerialBase {
   FORCE_INLINE void write(const char* str)                    { while (*str) write(*str++); }
   FORCE_INLINE void write(const uint8_t* buffer, size_t size) { while (size--) write(*buffer++); }
   FORCE_INLINE void print(const char* str)                    { write(str); }
-  FORCE_INLINE void print(char c, int base = 0)               { print((long)c, base); }
-  FORCE_INLINE void print(unsigned char c, int base = 0)      { print((unsigned long)c, base); }
-  FORCE_INLINE void print(int c, int base = DEC)              { print((long)c, base); }
-  FORCE_INLINE void print(unsigned int c, int base = DEC)     { print((unsigned long)c, base); }
+  NO_INLINE void print(char c, int base = 0)               { print((long)c, base); }
+  NO_INLINE void print(unsigned char c, int base = 0)      { print((unsigned long)c, base); }
+  NO_INLINE void print(int c, int base = DEC)              { print((long)c, base); }
+  NO_INLINE void print(unsigned int c, int base = DEC)     { print((unsigned long)c, base); }
   void print(long c, int base = DEC)            { if (!base) write(c); write((const uint8_t*)"-", c < 0); printNumber(c < 0 ? -c : c, base); }
   void print(unsigned long c, int base = DEC)   { printNumber(c, base); }
   void print(double c, int digits = 2)          { printFloat(c, digits); }
 
-  FORCE_INLINE void println(const char s[])                  { print(s); println(); }
-  FORCE_INLINE void println(char c, int base = 0)            { print(c, base); println(); }
-  FORCE_INLINE void println(unsigned char c, int base = 0)   { print(c, base); println(); }
-  FORCE_INLINE void println(int c, int base = DEC)           { print(c, base); println(); }
-  FORCE_INLINE void println(unsigned int c, int base = DEC)  { print(c, base); println(); }
-  FORCE_INLINE void println(long c, int base = DEC)          { print(c, base); println(); }
-  FORCE_INLINE void println(unsigned long c, int base = DEC) { print(c, base); println(); }
-  FORCE_INLINE void println(double c, int digits = 2)        { print(c, digits); println(); }
-  void println()                                { write("\r\n"); }
+  NO_INLINE void println(const char s[])                  { print(s); println(); }
+  NO_INLINE void println(char c, int base = 0)            { print(c, base); println(); }
+  NO_INLINE void println(unsigned char c, int base = 0)   { print(c, base); println(); }
+  NO_INLINE void println(int c, int base = DEC)           { print(c, base); println(); }
+  NO_INLINE void println(unsigned int c, int base = DEC)  { print(c, base); println(); }
+  NO_INLINE void println(long c, int base = DEC)          { print(c, base); println(); }
+  NO_INLINE void println(unsigned long c, int base = DEC) { print(c, base); println(); }
+  NO_INLINE void println(double c, int digits = 2)        { print(c, digits); println(); }
+  NO_INLINE void println()                                { write('\r'); write('\n'); }
 
   // Print a number with the given base
   void printNumber(unsigned long n, const uint8_t base) {
diff --git a/Marlin/src/core/serial_hook.h b/Marlin/src/core/serial_hook.h
index 17cf8bdd7d..e14b821a9c 100644
--- a/Marlin/src/core/serial_hook.h
+++ b/Marlin/src/core/serial_hook.h
@@ -61,7 +61,7 @@ struct ConditionalSerial : public SerialBase< ConditionalSerial<SerialT> > {
 
   bool    & condition;
   SerialT & out;
-  size_t write(uint8_t c) { if (condition) return out.write(c); return 0; }
+  NO_INLINE size_t write(uint8_t c) { if (condition) return out.write(c); return 0; }
   void flush()            { if (condition) out.flush();  }
   void begin(long br)     { out.begin(br); }
   void end()              { out.end(); }
@@ -83,7 +83,7 @@ struct ForwardSerial : public SerialBase< ForwardSerial<SerialT> > {
   typedef SerialBase< ForwardSerial<SerialT> > BaseClassT;
 
   SerialT & out;
-  size_t write(uint8_t c) { return out.write(c); }
+  NO_INLINE size_t write(uint8_t c) { return out.write(c); }
   void flush()            { out.flush();  }
   void begin(long br)     { out.begin(br); }
   void end()              { out.end(); }
@@ -111,12 +111,12 @@ struct RuntimeSerial : public SerialBase< RuntimeSerial<SerialT> >, public Seria
   EndOfMessageHook eofHook;
   void *           userPointer;
 
-  size_t write(uint8_t c) {
+  NO_INLINE size_t write(uint8_t c) {
     if (writeHook) writeHook(userPointer, c);
     return SerialT::write(c);
   }
 
-  void msgDone() {
+  NO_INLINE void msgDone() {
     if (eofHook) eofHook(userPointer);
   }
 
@@ -130,7 +130,11 @@ struct RuntimeSerial : public SerialBase< RuntimeSerial<SerialT> >, public Seria
 
   using BaseClassT::print;
   using BaseClassT::println;
-  
+
+  // Underlying implementation might use Arduino's bool operator
+  bool connected() { 
+    return Private::HasMember_connected<SerialT>::value ? CALL_IF_EXISTS(bool, static_cast<SerialT*>(this), connected) : static_cast<SerialT*>(this)->operator bool(); 
+  }  
 
   void setHook(WriteHook writeHook = 0, EndOfMessageHook eofHook = 0, void * userPointer = 0) {
     // Order is important here as serial code can be called inside interrupts
@@ -165,13 +169,13 @@ struct MultiSerial : public SerialBase< MultiSerial<Serial0T, Serial1T, offset>
     AllMask           = FirstOutputMask | SecondOutputMask,
   };
 
-  size_t write(uint8_t c) {
+  NO_INLINE size_t write(uint8_t c) {
     size_t ret = 0;
     if (portMask & FirstOutputMask)   ret = serial0.write(c);
     if (portMask & SecondOutputMask)  ret = serial1.write(c) | ret;
     return ret;
   }
-  void msgDone() {
+  NO_INLINE void msgDone() {
     if (portMask & FirstOutputMask)   serial0.msgDone();
     if (portMask & SecondOutputMask)  serial1.msgDone();
   }
@@ -182,7 +186,7 @@ struct MultiSerial : public SerialBase< MultiSerial<Serial0T, Serial1T, offset>
       default: return false;
     }
   }
-  int read(uint8_t index) {
+  NO_INLINE int read(uint8_t index) {
     switch(index) {
       case 0 + offset: return serial0.read();
       case 1 + offset: return serial1.read();
@@ -208,11 +212,11 @@ struct MultiSerial : public SerialBase< MultiSerial<Serial0T, Serial1T, offset>
   using BaseClassT::read;
 
   // Redirect flush
-  void flush()      {
+  NO_INLINE void flush()      {
     if (portMask & FirstOutputMask)   serial0.flush();
     if (portMask & SecondOutputMask)  serial1.flush();
   }
-  void flushTX()    {
+  NO_INLINE void flushTX()    {
     if (portMask & FirstOutputMask)   CALL_IF_EXISTS(void, &serial0, flushTX);
     if (portMask & SecondOutputMask)  CALL_IF_EXISTS(void, &serial1, flushTX);
   }