diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 3dbc48fd9bc..1d1b05969c6 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -434,7 +434,11 @@ matchmg(void)
 				ts.fn = mstart;
 				runcgo(libcgo_thread_start, &ts);
 			} else {
-				m->g0 = malg(8192);
+				if(Windows)
+					// windows will layout sched stack on os stack
+					m->g0 = malg(-1);
+				else
+					m->g0 = malg(8192);
 				newosproc(m, m->g0, m->g0->stackbase, mstart);
 			}
 		}
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 6e8a79624a7..ca76729ec20 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -232,9 +232,7 @@ struct	M
 	G*	lockedg;
 	uint64 freg[8];	// Floating point register storage used by ARM software fp routines
 #ifdef __WINDOWS__
-	void*	return_address;	// saved return address and stack
-	void*	stack_pointer;	// pointer for Windows stdcall
-	void*	os_stack_pointer;
+	void*	gostack;	// bookmark to keep track of go stack during stdcall
 #endif
 };
 struct	Stktop
@@ -289,6 +287,16 @@ struct	Func
 	int32	locals;	// number of 32-bit locals
 };
 
+#ifdef __WINDOWS__
+enum {
+   Windows = 1
+};
+#else
+enum {
+   Windows = 0
+};
+#endif
+
 /*
  * defined macros
  *    you need super-goru privilege
diff --git a/src/pkg/runtime/windows/386/sys.s b/src/pkg/runtime/windows/386/sys.s
index e36ef53e0a8..8c43f9bdcf1 100644
--- a/src/pkg/runtime/windows/386/sys.s
+++ b/src/pkg/runtime/windows/386/sys.s
@@ -12,87 +12,102 @@ TEXT get_kernel_module(SB),7,$0
 	MOVL	0x08(AX), AX		// get base of module
 	RET
 
-// void *stdcall_raw(void *fn, ...);
-// Call fn with stdcall calling convention.
-// fn parameters are on stack.
-TEXT stdcall_raw(SB),7,$0
-	get_tls(CX)
-	MOVL	m(CX), CX
-	POPL	m_return_address(CX)	// save return address
-	POPL	AX			// first arg is function pointer
-	MOVL	SP, m_stack_pointer(CX)	// save stack pointer
-	CALL	AX
-	get_tls(CX)
-	MOVL	m(CX), CX
-	MOVL	m_stack_pointer(CX), SP
-	PUSHL	AX
-	PUSHL	m_return_address(CX)
-	RET
+// void *stdcall_raw(void *fn, int32 count, uintptr *args)
+TEXT stdcall_raw(SB),7,$4
+	// Copy arguments from stack.
+	MOVL	fn+0(FP), AX
+	MOVL	count+4(FP), CX		// words
+	MOVL	args+8(FP), BP
 
-// void syscall(StdcallParams *p);
-// Call p.fn syscall + GetLastError on os stack.
-TEXT syscall(SB),7,$16
-	MOVL	p+0(FP), AX
-	MOVL	SP, CX
-
-	// Figure out if we need to switch to m->g0 stack.
+	// Switch to m->g0 if needed.
 	get_tls(DI)
 	MOVL	m(DI), DX
+	MOVL	g(DI), SI
+	MOVL	SI, 0(SP)		// save g
+	MOVL	SP, m_gostack(DX)	// save SP
 	MOVL	m_g0(DX), SI
 	CMPL	g(DI), SI
-	JEQ	2(PC)
+	JEQ 3(PC)
 	MOVL	(m_sched+gobuf_sp)(DX), SP
-
-	// Now on a scheduling stack (an os stack).
-	MOVL	g(DI), BP
-	MOVL	BP, 8(SP)
 	MOVL	SI, g(DI)
-	MOVL	CX, 4(SP)
-	MOVL	AX, 0(SP)
-	CALL	call_syscall(SB)
-	
-	// Back; switch to original g and stack, re-establish
-	// "DF is clear" invariant.
+
+	// Copy args to new stack.
+	SUBL	$(10*4), SP		// padding
+	MOVL	CX, BX
+	SALL	$2, BX
+	SUBL	BX, SP			// room for args
+	MOVL	SP, DI
+	MOVL	BP, SI
 	CLD
+	REP; MOVSL
+
+	// Call stdcall function.
+	CALL	AX
+
+	// Restore original SP, g.
 	get_tls(DI)
-	MOVL	8(SP), SI
+	MOVL	m(DI), DX
+	MOVL	m_gostack(DX), SP	// restore SP
+	MOVL	0(SP), SI		// restore g
 	MOVL	SI, g(DI)
-	MOVL	4(SP), SP
-	RET
 
-TEXT threadstart(SB),7,$0
-	MOVL	4(SP), AX		// threadstart param
-	MOVL	0(AX), BX		// newosproc arg stack
-	MOVL	0(BX), CX		// m
-	MOVL	4(BX), DX		// g
+	// Someday the convention will be D is always cleared.
+	CLD
 
-	// set up tls
+	RET 
+
+// void tstart(M *newm);
+TEXT tstart(SB),7,$0
+	MOVL	newm+4(SP), CX		// m
+	MOVL	m_g0(CX), DX		// g
+
+	MOVL	SP, DI			// remember stack
+
+	// Layout new m scheduler stack on os stack.
+	MOVL	SP, AX
+	SUBL	$256, AX		// just some space for ourselves
+	MOVL	AX, g_stackbase(DX)
+	SUBL	$8192, AX		// stack size
+	MOVL	AX, g_stackguard(DX)
+
+	// Set up tls.
 	LEAL	m_tls(CX), SI
 	MOVL	SI, 0x2c(FS)
 	MOVL	CX, m(SI)
 	MOVL	DX, g(SI)
-	MOVL	SP, m_os_stack_pointer(CX)
 
-	PUSHL	8(BX)			// stk
-	PUSHL	12(BX)			// fn
-	PUSHL	4(AX)			// event_handle
+	// Use scheduler stack now.
+	MOVL	g_stackbase(DX), SP
 
-	// signal that we're done with thread args
-	MOVL	SetEvent(SB), BX
-	CALL	BX			// SetEvent(event_handle)
-	POPL	BX			// fn
-	POPL	SP			// stk
+	// Someday the convention will be D is always cleared.
+	CLD
+
+	PUSHL	DI			// original stack
 
 	CALL	stackcheck(SB)		// clobbers AX,CX
-	CALL	BX			// fn()
 
-	// cleanup stack before returning as we are stdcall
-	get_tls(CX)
-	MOVL	m(CX), CX
-	MOVL	m_os_stack_pointer(CX), SP
-	POPL	AX			// return address
-	MOVL	AX, (SP)
-	XORL	AX, AX
+	CALL	mstart(SB)
+
+	POPL	DI			// original stack
+	MOVL	DI, SP
+
+	RET
+
+// uint32 tstart_stdcall(M *newm);
+TEXT tstart_stdcall(SB),7,$0
+	MOVL	newm+4(SP), BX
+
+	PUSHL	BX
+	CALL	tstart+0(SB)
+	POPL	BX
+
+	// Adjust stack for stdcall to return properly.
+	MOVL	(SP), AX		// save return address
+	ADDL	$4, SP			// remove single parameter
+	MOVL	AX, (SP)		// restore return address
+
+	XORL	AX, AX			// return 0 == success
+
 	RET
 
 // setldt(int entry, int address, int limit)
diff --git a/src/pkg/runtime/windows/os.h b/src/pkg/runtime/windows/os.h
index 68efaa036a7..343ddbccf96 100644
--- a/src/pkg/runtime/windows/os.h
+++ b/src/pkg/runtime/windows/os.h
@@ -19,13 +19,15 @@ void windows_goargs(void);
 // Get start address of symbol data in memory.
 void *get_symdat_addr(void);
 
-// Call a Windows function with stdcall conventions.
-void *stdcall_raw(void *fn, ...);
-
 // Call a Windows function with stdcall conventions,
 // and switch to os stack during the call.
+void *stdcall_raw(void *fn, int32 count, uintptr *args);
 void *stdcall(void *fn, int32 count, ...);
 
+// Function to be called by windows CreateTread
+// to start new os thread.
+uint32 tstart_stdcall(M *newm);
+
 // Call stdcall Windows function StdcallParams.fn
 // with params StdcallParams.args,
 // followed immediately by GetLastError call.
@@ -36,8 +38,9 @@ struct StdcallParams
 {
 	void	*fn;
 	uintptr args[12];
+	int32	n;
 	uintptr	r;
 	uintptr	err;
 };
-void call_syscall(void *args);
+
 void syscall(StdcallParams *p);
diff --git a/src/pkg/runtime/windows/syscall.goc b/src/pkg/runtime/windows/syscall.goc
index 8287e704146..306b7152964 100644
--- a/src/pkg/runtime/windows/syscall.goc
+++ b/src/pkg/runtime/windows/syscall.goc
@@ -12,9 +12,8 @@ func loadlibraryex(filename uintptr) (handle uint32) {
 	p.args[0] = filename;
 	p.args[1] = 0;
 	p.args[2] = 0;
-	·entersyscall();
+	p.n = 3;
 	syscall(&p);
-	·exitsyscall();
 	handle = p.r;
 }
 
@@ -23,9 +22,8 @@ func getprocaddress(handle uint32, procname uintptr) (proc uintptr) {
 	p.fn = (void*)GetProcAddress;
 	p.args[0] = handle;
 	p.args[1] = procname;
-	·entersyscall();
+	p.n = 2;
 	syscall(&p);
-	·exitsyscall();
 	proc = p.r;
 }
 
@@ -35,9 +33,8 @@ func Syscall(trap uintptr, a1 uintptr, a2 uintptr, a3 uintptr) (r1 uintptr, r2 u
 	p.args[0] = a1;
 	p.args[1] = a2;
 	p.args[2] = a3;
-	·entersyscall();
+	p.n = 3;
 	syscall(&p);
-	·exitsyscall();
 	r1 = p.r;
 	r2 = 0;
 	err = p.err;
@@ -52,9 +49,8 @@ func Syscall6(trap uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4 uintptr, a5 u
 	p.args[3] = a4;
 	p.args[4] = a5;
 	p.args[5] = a6;
-	·entersyscall();
+	p.n = 6;
 	syscall(&p);
-	·exitsyscall();
 	r1 = p.r;
 	r2 = 0;
 	err = p.err;
@@ -72,9 +68,8 @@ func Syscall9(trap uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4 uintptr, a5 u
 	p.args[6] = a7;
 	p.args[7] = a8;
 	p.args[8] = a9;
-	·entersyscall();
+	p.n = 9;
 	syscall(&p);
-	·exitsyscall();
 	r1 = p.r;
 	r2 = 0;
 	lasterr = p.err;
@@ -95,9 +90,8 @@ func Syscall12(trap uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4 uintptr, a5
 	p.args[9] = a10;
 	p.args[10] = a11;
 	p.args[11] = a12;
-	·entersyscall();
+	p.n = 12;
 	syscall(&p);
-	·exitsyscall();
 	r1 = p.r;
 	r2 = 0;
 	lasterr = p.err;
@@ -109,6 +103,7 @@ func RawSyscall(trap uintptr, a1 uintptr, a2 uintptr, a3 uintptr) (r1 uintptr, r
 	p.args[0] = a1;
 	p.args[1] = a2;
 	p.args[2] = a3;
+	p.n = 3;
 	syscall(&p);
 	r1 = p.r;
 	r2 = 0;
diff --git a/src/pkg/runtime/windows/thread.c b/src/pkg/runtime/windows/thread.c
index a9062250dc7..82d1fa84e56 100644
--- a/src/pkg/runtime/windows/thread.c
+++ b/src/pkg/runtime/windows/thread.c
@@ -77,8 +77,8 @@ get_proc_addr(void *library, void *name)
 {
 	void *base;
 
-	base = stdcall_raw(LoadLibraryEx, library, 0, 0);
-	return stdcall_raw(GetProcAddress, base, name);
+	base = stdcall(LoadLibraryEx, 3, library, 0, 0);
+	return stdcall(GetProcAddress, 2, base, name);
 }
 
 void
@@ -251,17 +251,11 @@ notesleep(Note *n)
 void
 newosproc(M *m, G *g, void *stk, void (*fn)(void))
 {
-	struct {
-		void *args;
-		void *event_handle;
-	} param = { &m };
-	extern uint32 threadstart(void *p);
+	USED(stk);
+	USED(g);	// assuming g = m->g0
+	USED(fn);	// assuming fn = mstart
 
-	USED(g, stk, fn);
-	param.event_handle = stdcall(CreateEvent, 4, 0, 0, 0, 0);
-	stdcall(CreateThread, 6, 0, 0, threadstart, &param, 0, 0);
-	stdcall(WaitForSingleObject, 2, param.event_handle, -1);
-	stdcall(CloseHandle, 1, param.event_handle);
+	stdcall(CreateThread, 6, 0, 0, tstart_stdcall, m, 0, 0);
 }
 
 // Called to initialize a new m (including the bootstrap m).
@@ -275,25 +269,20 @@ minit(void)
 void *
 stdcall(void *fn, int32 count, ...)
 {
-	uintptr *a;
-	StdcallParams p;
-
-	p.fn = fn;
-	a = (uintptr*)(&count + 1);
-	while(count > 0) {
-		count--;
-		p.args[count] = a[count];
-	}
-	syscall(&p);
-	return (void*)(p.r);
+	return stdcall_raw(fn, count, (uintptr*)(&count + 1));
 }
 
 void
-call_syscall(void *args)
+syscall(StdcallParams *p)
 {
-	StdcallParams *p = (StdcallParams*)args;
-	stdcall_raw(SetLastError, 0);
-	p->r = (uintptr)stdcall_raw((void*)p->fn, p->args[0], p->args[1], p->args[2], p->args[3], p->args[4], p->args[5], p->args[6], p->args[7], p->args[8], p->args[9], p->args[10], p->args[11]);
-	p->err = (uintptr)stdcall_raw(GetLastError);
-	return;
+	uintptr a;
+
+	·entersyscall();
+	// TODO(brainman): Move calls to SetLastError and GetLastError
+	// to stdcall_raw to speed up syscall.
+	a = 0;
+	stdcall_raw(SetLastError, 1, &a);
+	p->r = (uintptr)stdcall_raw((void*)p->fn, p->n, p->args);
+	p->err = (uintptr)stdcall_raw(GetLastError, 0, &a);
+	·exitsyscall();
 }