diff --git a/arch/x86/include/asm/gdt.h b/arch/x86/include/asm/gdt.h
index 8df3115f..75f8ffe8 100644
--- a/arch/x86/include/asm/gdt.h
+++ b/arch/x86/include/asm/gdt.h
@@ -101,7 +101,12 @@ typedef struct {
 } __attribute__ ((packed)) gdt_ptr_t;
 
 /// Defines the maximum number of GDT entries
-#define GDT_ENTRIES     (5+MAX_TASKS)
+#ifdef CONFIG_X86_32
+#define GDT_ENTRIES	(5+MAX_TASKS)
+#else
+// a TSS descriptor is twice larger than a code/data descriptor
+#define GDT_ENTRIES	(5+MAX_TASKS*2)
+#endif
 #if GDT_ENTRIES > 8192
 #error Too many GDT entries!
 #endif
diff --git a/arch/x86/include/asm/tasks.h b/arch/x86/include/asm/tasks.h
index fc138802..cc548423 100644
--- a/arch/x86/include/asm/tasks.h
+++ b/arch/x86/include/asm/tasks.h
@@ -77,9 +77,18 @@ int create_default_frame(task_t* task, entry_point_t ep, void* arg);
  *
  * @return
  * - 0 on success
- * - -EINVAL (-22) on failure
  */
-int register_task(void);
+static inline int register_task(void)
+{
+#ifdef CONFIG_X86_32
+	uint16_t sel = (CORE_ID+5) << 3;
+#else
+	uint16_t sel = (CORE_ID*2+5) << 3;
+#endif
+	asm volatile ("ltr %%ax" : : "a"(sel));
+
+	return 0;
+}
 
 /** @brief Jump back to user code
  *
diff --git a/arch/x86/include/asm/tss.h b/arch/x86/include/asm/tss.h
index 17b2e8ab..03540957 100644
--- a/arch/x86/include/asm/tss.h
+++ b/arch/x86/include/asm/tss.h
@@ -70,8 +70,7 @@ typedef struct {
 	uint64_t	ist_rsp5;
 	uint64_t	ist_rsp6;
 	uint64_t	ist_rsp7;
-	uint32_t	res4;		// reserved entries
-	uint32_t	res5;		// reserved entries
+	uint32_t	res4, res5;	// reserved entries
 	uint16_t	res6, bitmap;
 #endif
 } __attribute__ ((packed)) tss_t;
diff --git a/arch/x86/kernel/entry32.asm b/arch/x86/kernel/entry32.asm
index 49e30351..7443ff7f 100644
--- a/arch/x86/kernel/entry32.asm
+++ b/arch/x86/kernel/entry32.asm
@@ -48,14 +48,6 @@ mboot:
     dd MULTIBOOT_HEADER_MAGIC
     dd MULTIBOOT_HEADER_FLAGS
     dd MULTIBOOT_CHECKSUM
-    
-    ; AOUT kludge - must be physical addresses. Make a note of these:
-    ; The linker script fills in the data for these ones!
-    ; dd mboot
-    ; dd code
-    ; dd bss
-    ; dd end
-    ; dd start
 
 msg db "?ello from MetalSVM kernel!!", 0
 
diff --git a/arch/x86/kernel/gdt.c b/arch/x86/kernel/gdt.c
index 9dce69ac..c625c8c1 100644
--- a/arch/x86/kernel/gdt.c
+++ b/arch/x86/kernel/gdt.c
@@ -29,7 +29,7 @@
 gdt_ptr_t				gp;
 tss_t					task_state_segments[MAX_CORES] __attribute__ ((aligned (PAGE_SIZE)));
 static unsigned char			kstacks[MAX_TASKS][KERNEL_STACK_SIZE] __attribute__ ((aligned (PAGE_SIZE))) = {[0 ... MAX_TASKS-1][0 ... KERNEL_STACK_SIZE-1] = 0xCD};
-size_t					default_stack_pointer = (size_t) kstacks[0] + KERNEL_STACK_SIZE - sizeof(size_t);
+size_t					default_stack_pointer = (size_t) kstacks[0] + KERNEL_STACK_SIZE - 16; // => stack is 16byte aligned 
 // currently, our kernel has full access to the ioports
 static gdt_entry_t			gdt[GDT_ENTRIES] = {[0 ... GDT_ENTRIES-1] = {0, 0, 0, 0, 0, 0}};
 
@@ -52,17 +52,7 @@ size_t get_stack(uint32_t id)
 {
 	if (BUILTIN_EXPECT(id >= MAX_TASKS, 0))
 		return -EINVAL;
-	return (size_t) kstacks[id] + KERNEL_STACK_SIZE - sizeof(size_t);
-}
-
-int register_task(void) 
-{
-	uint16_t sel;
-
-	sel = (CORE_ID+5) << 3;
-	asm volatile ("ltr %%ax" : : "a"(sel));
-
-	return 0;
+	return (size_t) kstacks[id] + KERNEL_STACK_SIZE - 16; // => stack is 16byte aligned 
 }
 
 int arch_fork(task_t* task)
@@ -229,14 +219,17 @@ static void gdt_set_gate(int num, unsigned long base, unsigned long limit,
  */
 void gdt_install(void)
 {
-	unsigned int i, mode;
+	unsigned int i;
+	unsigned long mode, limit;
 
 	memset(task_state_segments, 0x00, MAX_CORES*sizeof(tss_t));
 
 #ifdef CONFIG_X86_32
 	mode = GDT_FLAG_32_BIT;
+	limit = 0xFFFFFFFF;
 #elif defined(CONFIG_X86_64)
 	mode = GDT_FLAG_64_BIT;
+	limit = 0;
 #else
 #error invalid mode
 #endif
@@ -253,7 +246,7 @@ void gdt_install(void)
 	 * is 0, the limit is 4 GByte, it uses 4KByte granularity,
 	 * uses 32-bit opcodes, and is a Code Segment descriptor.
 	 */
-	gdt_set_gate(1, 0, 0xFFFFFFFF,
+	gdt_set_gate(1, 0, limit,
 		GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT,
 		GDT_FLAG_4K_GRAN | mode);
 
@@ -262,21 +255,21 @@ void gdt_install(void)
 	 * same as our code segment, but the descriptor type in
 	 * this entry's access byte says it's a Data Segment 
 	 */
-	gdt_set_gate(2, 0, 0xFFFFFFFF,
+	gdt_set_gate(2, 0, limit,
 		GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
 		GDT_FLAG_4K_GRAN | mode);
 		
 	/*
 	 * Create code segement for userspace applications (ring 3)
 	 */
-	gdt_set_gate(3, 0, 0xFFFFFFFF,
+	gdt_set_gate(3, 0, limit,
 		GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT,
 		GDT_FLAG_4K_GRAN | mode);
 
 	/*
 	 * Create data segement for userspace applications (ring 3)
 	 */
-	gdt_set_gate(4, 0, 0xFFFFFFFF,
+	gdt_set_gate(4, 0, limit,
                 GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
                 GDT_FLAG_4K_GRAN | mode);
 
@@ -289,12 +282,13 @@ void gdt_install(void)
 		task_state_segments[i].eflags = 0x1202;
 		task_state_segments[i].ss0 = 0x10;		// data segment
 		task_state_segments[i].esp0 = 0xDEADBEEF;	// invalid pseudo address
+		gdt_set_gate(5+i, (unsigned long) (task_state_segments+i), sizeof(tss_t)-1,
+			GDT_FLAG_PRESENT | GDT_FLAG_TSS | GDT_FLAG_RING0, mode);
 #elif defined(CONFIG_X86_64)
 		task_state_segments[i].rsp0 = 0xDEADBEEF;       // invalid pseudo address
+		gdt_set_gate(5+i*2, (unsigned long) (task_state_segments+i), sizeof(tss_t)-1,
+			GDT_FLAG_PRESENT | GDT_FLAG_TSS | GDT_FLAG_RING0, mode);
 #endif
-
-		gdt_set_gate(5+i, (unsigned long) (task_state_segments+i), sizeof(tss_t)-1,
-			GDT_FLAG_PRESENT | GDT_FLAG_TSS | GDT_FLAG_RING0, 0);
 	}
 
 	/* Flush out the old GDT and install the new changes! */
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index c14bfeea..aad89b70 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -39,7 +39,11 @@
  * for which the 'presence' bit is cleared (0) will generate an
  * "Unhandled Interrupt" exception 
  */
+#ifdef CONFIG_X86_64
+static idt_entry_t idt[256] = {[0 ... 255] = {0, 0, 0, 0, 0, 0, 0}};
+#else
 static idt_entry_t idt[256] = {[0 ... 255] = {0, 0, 0, 0, 0}};
+#endif
 static idt_ptr_t idtp;
 
 /*
diff --git a/include/metalsvm/ctype.h b/include/metalsvm/ctype.h
index 5ea30971..1bf5f7fd 100644
--- a/include/metalsvm/ctype.h
+++ b/include/metalsvm/ctype.h
@@ -35,7 +35,7 @@ static inline int isascii(int c)
 
 /** Applies an and-operation to 
  * push the value of 'c' into the ASCII-range */
-static inline int toascii(c)
+static inline int toascii(int c)
 {
 	return (((unsigned char)(c))&0x7f);
 }