diff --git a/demos/STM32/RT-STM32G474RE-NUCLEO64-SB_HOST_STATIC/readme_debug.txt b/demos/STM32/RT-STM32G474RE-NUCLEO64-SB_HOST_STATIC/readme_debug.txt
index 4536bbd50..1be276057 100644
--- a/demos/STM32/RT-STM32G474RE-NUCLEO64-SB_HOST_STATIC/readme_debug.txt
+++ b/demos/STM32/RT-STM32G474RE-NUCLEO64-SB_HOST_STATIC/readme_debug.txt
@@ -4,9 +4,10 @@ The launch configurations under:
 
 Contain hardcoded paths prefixed like:
 
-  /home/giovanni/Projects/ChibiStudio/chibios_trunk/demos/various/SB-CLIENT-32k-08070000-4k-2001E000/build/sb.elf
+  /home/giovanni/Projects/ChibiStudio/chibios_trunk/demos/various/SB-CLIENT-128k-08040000-4k-2001E000/build/sb.elf
 
 Replace the initial part up to "chibios_trunk" with the path of your ChibiOS
 directory before attempting a debug session using Eclipse. In addition, you
-need also to compile the "SB-CLIENT-32k-08070000-4k-2001E000" project, its
-image (sb.elf) is loaded inside the demo sandbox.
+need also to compile the "SB-CLIENT-128k-08040000-16k-20018000" and
+"SB-CLIENT-128k-08060000-16k-2001C000" projects, their image (sb.elf) is
+ loaded inside the demo sandboxes.
diff --git a/os/common/ports/ARMv7-M-ALT/chcore.c b/os/common/ports/ARMv7-M-ALT/chcore.c
index cc26279a9..e4ed1fe27 100644
--- a/os/common/ports/ARMv7-M-ALT/chcore.c
+++ b/os/common/ports/ARMv7-M-ALT/chcore.c
@@ -68,38 +68,18 @@ CC_NO_INLINE uint32_t port_get_s_psp(void) {
   return (uint32_t)__port_syscall_get_s_psp(__sch_get_currthread());
 }
 
-CC_WEAK void port_syscall(struct port_extctx *ctxp, uint32_t n) {
+CC_WEAK void __port_do_fastcall_entry(uint32_t n) {
 
-  (void)ctxp;
   (void)n;
 
-  chSysHalt("unimplemented syscall");
+  chSysHalt("unimplemented fastcall");
 }
 
 CC_WEAK void __port_do_syscall_entry(uint32_t n) {
-  thread_t *tp = __sch_get_currthread();
-  struct port_extctx *ectxp, *newctxp;
-  uint32_t u_psp;
 
-  /* Caller context in unprivileged memory.*/
-  u_psp = __get_PSP();
-  ectxp = (struct port_extctx *)u_psp;
-  __port_syscall_set_u_psp(tp, u_psp);
+  (void)n;
 
-  /* Return context for change in privileged mode.*/
-  newctxp = ((struct port_extctx *)__port_syscall_get_s_psp(tp)) - 1;
-
-  /* Creating context for return in privileged mode.*/
-  newctxp->r0    = (uint32_t)ectxp;
-  newctxp->r1    = n;
-  newctxp->pc    = (uint32_t)port_syscall;
-  newctxp->xpsr  = 0x01000000U;
-#if CORTEX_USE_FPU == TRUE
-  newctxp->fpscr = FPU->FPDSCR;
-#endif
-
-  /* Switching PSP to the privileged mode PSP.*/
-  __set_PSP((uint32_t)newctxp);
+  chSysHalt("unimplemented syscall");
 }
 
 CC_WEAK void __port_do_syscall_return(void) {
diff --git a/os/common/ports/ARMv7-M-ALT/compilers/GCC/chcoreasm.S b/os/common/ports/ARMv7-M-ALT/compilers/GCC/chcoreasm.S
index 4d8f40452..0d325b6eb 100644
--- a/os/common/ports/ARMv7-M-ALT/compilers/GCC/chcoreasm.S
+++ b/os/common/ports/ARMv7-M-ALT/compilers/GCC/chcoreasm.S
@@ -230,6 +230,8 @@ SVC_Handler:
                 ldr     r3, [r2, #24]       /* PC position. */
                 ldrh    r0, [r3, #-2]       /* SVC opcode.  */
                 and     r0, #255
+//                cmp     r0, #0xF0
+//                bge     __port_do_fastcall_entry
                 b       __port_do_syscall_entry
 
 frompriv:
diff --git a/os/sb/host/compilers/GCC/sbexc.S b/os/sb/host/compilers/GCC/sbexc.S
index f38bfdfc9..4abc55cda 100644
--- a/os/sb/host/compilers/GCC/sbexc.S
+++ b/os/sb/host/compilers/GCC/sbexc.S
@@ -49,8 +49,8 @@
 
                 .align      2
                 .thumb_func
-                .global     port_syscall
-port_syscall:
+                .global     __sb_dispatch_syscall
+__sb_dispatch_syscall:
                 ldr         r3, =sb_syscalls
                 ldr.w       r3, [r3, r1, lsl #2]
                 blx         r3
diff --git a/os/sb/host/sbapi.c b/os/sb/host/sbapi.c
index bb0b56798..f6b065127 100644
--- a/os/sb/host/sbapi.c
+++ b/os/sb/host/sbapi.c
@@ -1232,4 +1232,31 @@ void __sb_abort(msg_t msg) {
   chSysHalt("zombies");
 }
 
+void __port_do_syscall_entry(uint32_t n) {
+  extern void __sb_dispatch_syscall(struct port_extctx *ctxp, uint32_t n);
+  thread_t *tp = __sch_get_currthread();
+  struct port_extctx *ectxp, *newctxp;
+  uint32_t u_psp;
+
+  /* Caller context in unprivileged memory.*/
+  u_psp = __get_PSP();
+  ectxp = (struct port_extctx *)u_psp;
+  __port_syscall_set_u_psp(tp, u_psp);
+
+  /* Return context for change in privileged mode.*/
+  newctxp = ((struct port_extctx *)__port_syscall_get_s_psp(tp)) - 1;
+
+  /* Creating context for return in privileged mode.*/
+  newctxp->r0    = (uint32_t)ectxp;
+  newctxp->r1    = n;
+  newctxp->pc    = (uint32_t)__sb_dispatch_syscall;
+  newctxp->xpsr  = 0x01000000U;
+#if CORTEX_USE_FPU == TRUE
+  newctxp->fpscr = FPU->FPDSCR;
+#endif
+
+  /* Switching PSP to the privileged mode PSP.*/
+  __set_PSP((uint32_t)newctxp);
+}
+
 /** @} */
diff --git a/os/sb/host/sbhost.h b/os/sb/host/sbhost.h
index ca34974f6..d6a99ff78 100644
--- a/os/sb/host/sbhost.h
+++ b/os/sb/host/sbhost.h
@@ -57,7 +57,6 @@ extern sb_t sb;
 #ifdef __cplusplus
 extern "C" {
 #endif
-  void port_syscall(struct port_extctx *ctxp, uint32_t n);
   size_t sb_strv_getsize(const char *v[], int *np);
   void sb_strv_copy(const char *sp[], void *dp, int n);
   bool sb_is_valid_read_range(sb_class_t *sbp, const void *start, size_t size);