diff --git a/headers/os/arch/x86_64/arch_debugger.h b/headers/os/arch/x86_64/arch_debugger.h
index e4607d2fd9..ca89c14825 100644
--- a/headers/os/arch/x86_64/arch_debugger.h
+++ b/headers/os/arch/x86_64/arch_debugger.h
@@ -6,38 +6,14 @@
 #define _ARCH_X86_64_DEBUGGER_H
 
 
-typedef struct x86_64_fp_register {
-	uint8		value[10];
-	uint8		reserved[6];
-} x86_64_fp_register;
+#if __x86_64__
 
 
-typedef struct x86_64_xmm_register {
-	uint8		value[16];
-} x86_64_xmm_register;
-
-
-typedef struct x86_64_extended_registers {
-	uint16					control;
-	uint16					status;
-	uint8					tag;
-	uint8					reserved1;
-	uint16					opcode;
-	uint64					instruction_pointer;
-	uint64					data_pointer;
-	uint32					mxcsr;
-	uint32					mxcsr_mask;
-	union {
-		x86_64_fp_register	fp_registers[8];	// st0-st7
-		x86_64_fp_register	mmx_registers[8];	// mm0-mm7
-	};
-	x86_64_xmm_register		xmm_registers[16];	// xmm0-xmm15
-	uint8					reserved2[96];		// 416 - 512
-} x86_64_extended_registers;
+#include <posix/arch/x86_64/signal.h>
 
 
 struct x86_64_debug_cpu_state {
-	x86_64_extended_registers	extended_registers;
+	struct savefpu	extended_registers;
 
 	uint64	gs;
 	uint64	fs;
@@ -68,4 +44,7 @@ struct x86_64_debug_cpu_state {
 } __attribute__((aligned(16)));
 
 
+#endif
+
+
 #endif	// _ARCH_X86_64_DEBUGGER_H
diff --git a/headers/posix/arch/x86_64/signal.h b/headers/posix/arch/x86_64/signal.h
index ad4fa4b128..e9146569ea 100644
--- a/headers/posix/arch/x86_64/signal.h
+++ b/headers/posix/arch/x86_64/signal.h
@@ -12,64 +12,18 @@
 
 #if __x86_64__
 
-
-struct fp_stack {
-	unsigned char		st0[10];
-	unsigned char		_reserved_42_47[6];
-	unsigned char		st1[10];
-	unsigned char		_reserved_58_63[6];
-	unsigned char		st2[10];
-	unsigned char		_reserved_74_79[6];
-	unsigned char		st3[10];
-	unsigned char		_reserved_90_95[6];
-	unsigned char		st4[10];
-	unsigned char		_reserved_106_111[6];
-	unsigned char		st5[10];
-	unsigned char		_reserved_122_127[6];
-	unsigned char		st6[10];
-	unsigned char		_reserved_138_143[6];
-	unsigned char		st7[10];
-	unsigned char		_reserved_154_159[6];
+struct x86_64_fp_register {
+	unsigned char value[10];
+	unsigned char reserved[6];
 };
 
-struct mmx_regs {
-	unsigned char		mm0[10];
-	unsigned char		_reserved_42_47[6];
-	unsigned char		mm1[10];
-	unsigned char		_reserved_58_63[6];
-	unsigned char		mm2[10];
-	unsigned char		_reserved_74_79[6];
-	unsigned char		mm3[10];
-	unsigned char		_reserved_90_95[6];
-	unsigned char		mm4[10];
-	unsigned char		_reserved_106_111[6];
-	unsigned char		mm5[10];
-	unsigned char		_reserved_122_127[6];
-	unsigned char		mm6[10];
-	unsigned char		_reserved_138_143[6];
-	unsigned char		mm7[10];
-	unsigned char		_reserved_154_159[6];
+
+struct x86_64_xmm_register {
+	unsigned char value[16];
 };
 
-struct xmm_regs {
-	unsigned char		xmm0[16];
-	unsigned char		xmm1[16];
-	unsigned char		xmm2[16];
-	unsigned char		xmm3[16];
-	unsigned char		xmm4[16];
-	unsigned char		xmm5[16];
-	unsigned char		xmm6[16];
-	unsigned char		xmm7[16];
-	unsigned char		xmm8[16];
-	unsigned char		xmm9[16];
-	unsigned char		xmm10[16];
-	unsigned char		xmm11[16];
-	unsigned char		xmm12[16];
-	unsigned char		xmm13[16];
-	unsigned char		xmm14[16];
-	unsigned char		xmm15[16];
-};
 
+// The layout of this struct matches the one used by the FXSAVE instruction
 struct fpu_state {
 	unsigned short		control;
 	unsigned short		status;
@@ -81,26 +35,33 @@ struct fpu_state {
 	unsigned int		mscsr_mask;
 
 	union {
-		struct fp_stack	fp;
-		struct mmx_regs	mmx;
+		struct x86_64_fp_register fp[8];
+		struct x86_64_fp_register mmx[8];
 	};
 
-	struct xmm_regs		xmm;
+	struct x86_64_xmm_register		xmm[16];
 	unsigned char		_reserved_416_511[96];
 };
 
+
 struct xstate_hdr {
 	unsigned long		bv;
 	unsigned long		xcomp_bv;
 	unsigned char		_reserved[48];
 };
 
+
+// The layout of this struct matches the one used by the FXSAVE instruction on
+// an AVX CPU
 struct savefpu {
-	struct fpu_state	fp_fxsave;
-	struct xstate_hdr	fp_xstate;
-	unsigned long		fp_ymm[16][2];
+	struct fpu_state			fp_fxsave;
+	struct xstate_hdr			fp_xstate;
+	struct x86_64_xmm_register	fp_ymm[16];
+		// The high half of the YMM registers, to combine with the low half
+		// found in fp_fxsave.xmm
 };
 
+
 struct vregs {
 	unsigned long		rax;
 	unsigned long		rbx;
diff --git a/src/kits/debugger/arch/x86_64/ArchitectureX8664.cpp b/src/kits/debugger/arch/x86_64/ArchitectureX8664.cpp
index cb03343633..995ecee58f 100644
--- a/src/kits/debugger/arch/x86_64/ArchitectureX8664.cpp
+++ b/src/kits/debugger/arch/x86_64/ArchitectureX8664.cpp
@@ -29,6 +29,7 @@
 
 #include "disasm/DisassemblerX8664.h"
 
+#define X86_64_EXTENDED_FEATURE_AVX	(1 << 28)
 
 static const int32 kFromDwarfRegisters[] = {
 	X86_64_REGISTER_RAX,
@@ -170,6 +171,20 @@ ArchitectureX8664::Init()
 	if (fAssemblyLanguage == NULL)
 		return B_NO_MEMORY;
 
+	int featureFlags = 0;
+#ifdef __x86_64__
+	// TODO: this needs to be determined/retrieved indirectly from the
+	// target host interface, as in the remote case the CPU features may
+	// differ from those of the local CPU.
+	cpuid_info info;
+	status_t error = get_cpuid(&info, 1, 0);
+	if (error != B_OK)
+		return error;
+
+	if ((info.eax_1.extended_features & X86_64_EXTENDED_FEATURE_AVX) != 0)
+		featureFlags |= X86_64_CPU_FEATURE_FLAG_AVX;
+#endif
+
 	try {
 		_AddIntegerRegister(X86_64_REGISTER_RIP, "rip", B_UINT64_TYPE,
 			REGISTER_TYPE_INSTRUCTION_POINTER, false);
@@ -240,38 +255,73 @@ ArchitectureX8664::Init()
 		_AddSIMDRegister(X86_64_REGISTER_MM6, "mm6", sizeof(uint64));
 		_AddSIMDRegister(X86_64_REGISTER_MM7, "mm7", sizeof(uint64));
 
-		_AddSIMDRegister(X86_64_REGISTER_XMM0, "xmm0",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM1, "xmm1",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM2, "xmm2",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM3, "xmm3",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM4, "xmm4",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM5, "xmm5",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM6, "xmm6",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM7, "xmm7",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM8, "xmm8",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM9, "xmm9",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM10, "xmm10",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM11, "xmm11",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM12, "xmm12",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM13, "xmm13",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM14, "xmm14",
-			sizeof(x86_64_xmm_register));
-		_AddSIMDRegister(X86_64_REGISTER_XMM15, "xmm15",
-			sizeof(x86_64_xmm_register));
+		if ((featureFlags & X86_64_CPU_FEATURE_FLAG_AVX) != 0) {
+			_AddSIMDRegister(X86_64_REGISTER_XMM0, "ymm0",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM1, "ymm1",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM2, "ymm2",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM3, "ymm3",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM4, "ymm4",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM5, "ymm5",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM6, "ymm6",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM7, "ymm7",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM8, "ymm8",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM9, "ymm9",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM10, "ymm10",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM11, "ymm11",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM12, "ymm12",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM13, "ymm13",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM14, "ymm14",
+					sizeof(x86_64_xmm_register) * 2);
+			_AddSIMDRegister(X86_64_REGISTER_XMM15, "ymm15",
+					sizeof(x86_64_xmm_register) * 2);
+		} else {
+			_AddSIMDRegister(X86_64_REGISTER_XMM0, "xmm0",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM1, "xmm1",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM2, "xmm2",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM3, "xmm3",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM4, "xmm4",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM5, "xmm5",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM6, "xmm6",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM7, "xmm7",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM8, "xmm8",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM9, "xmm9",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM10, "xmm10",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM11, "xmm11",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM12, "xmm12",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM13, "xmm13",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM14, "xmm14",
+					sizeof(x86_64_xmm_register));
+			_AddSIMDRegister(X86_64_REGISTER_XMM15, "xmm15",
+					sizeof(x86_64_xmm_register));
+		}
 
 	} catch (std::bad_alloc&) {
 		return B_NO_MEMORY;
diff --git a/src/kits/debugger/arch/x86_64/ArchitectureX8664.h b/src/kits/debugger/arch/x86_64/ArchitectureX8664.h
index dfeb2ed886..6d84c908b0 100644
--- a/src/kits/debugger/arch/x86_64/ArchitectureX8664.h
+++ b/src/kits/debugger/arch/x86_64/ArchitectureX8664.h
@@ -14,6 +14,13 @@
 #include "Register.h"
 
 
+enum {
+	X86_64_CPU_FEATURE_FLAG_NONE = 0,
+	X86_64_CPU_FEATURE_FLAG_AVX = 1,
+	X86_64_CPU_FEATURE_FLAG_AVX512 = 2
+};
+
+
 class SourceLanguage;
 
 
diff --git a/src/kits/debugger/arch/x86_64/CpuStateX8664.cpp b/src/kits/debugger/arch/x86_64/CpuStateX8664.cpp
index 36e4b089b8..00c9946c5a 100644
--- a/src/kits/debugger/arch/x86_64/CpuStateX8664.cpp
+++ b/src/kits/debugger/arch/x86_64/CpuStateX8664.cpp
@@ -50,50 +50,70 @@ CpuStateX8664::CpuStateX8664(const x86_64_debug_cpu_state& state)
 	SetIntRegister(X86_64_REGISTER_GS, state.gs);
 	SetIntRegister(X86_64_REGISTER_SS, state.ss);
 
-	const x86_64_extended_registers& extended = state.extended_registers;
+	const struct savefpu& extended = state.extended_registers;
 
 	SetFloatRegister(X86_64_REGISTER_ST0,
-		(double)(*(long double*)(extended.fp_registers[0].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[0].value)));
 	SetFloatRegister(X86_64_REGISTER_ST1,
-		(double)(*(long double*)(extended.fp_registers[1].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[1].value)));
 	SetFloatRegister(X86_64_REGISTER_ST2,
-		(double)(*(long double*)(extended.fp_registers[2].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[2].value)));
 	SetFloatRegister(X86_64_REGISTER_ST3,
-		(double)(*(long double*)(extended.fp_registers[3].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[3].value)));
 	SetFloatRegister(X86_64_REGISTER_ST4,
-		(double)(*(long double*)(extended.fp_registers[4].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[4].value)));
 	SetFloatRegister(X86_64_REGISTER_ST5,
-		(double)(*(long double*)(extended.fp_registers[5].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[5].value)));
 	SetFloatRegister(X86_64_REGISTER_ST6,
-		(double)(*(long double*)(extended.fp_registers[6].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[6].value)));
 	SetFloatRegister(X86_64_REGISTER_ST7,
-		(double)(*(long double*)(extended.fp_registers[7].value)));
+		(double)(*(long double*)(extended.fp_fxsave.fp[7].value)));
 
-	SetMMXRegister(X86_64_REGISTER_MM0, extended.mmx_registers[0].value);
-	SetMMXRegister(X86_64_REGISTER_MM1, extended.mmx_registers[1].value);
-	SetMMXRegister(X86_64_REGISTER_MM2, extended.mmx_registers[2].value);
-	SetMMXRegister(X86_64_REGISTER_MM3, extended.mmx_registers[3].value);
-	SetMMXRegister(X86_64_REGISTER_MM4, extended.mmx_registers[4].value);
-	SetMMXRegister(X86_64_REGISTER_MM5, extended.mmx_registers[5].value);
-	SetMMXRegister(X86_64_REGISTER_MM6, extended.mmx_registers[6].value);
-	SetMMXRegister(X86_64_REGISTER_MM7, extended.mmx_registers[7].value);
+	SetMMXRegister(X86_64_REGISTER_MM0, extended.fp_fxsave.mmx[0].value);
+	SetMMXRegister(X86_64_REGISTER_MM1, extended.fp_fxsave.mmx[1].value);
+	SetMMXRegister(X86_64_REGISTER_MM2, extended.fp_fxsave.mmx[2].value);
+	SetMMXRegister(X86_64_REGISTER_MM3, extended.fp_fxsave.mmx[3].value);
+	SetMMXRegister(X86_64_REGISTER_MM4, extended.fp_fxsave.mmx[4].value);
+	SetMMXRegister(X86_64_REGISTER_MM5, extended.fp_fxsave.mmx[5].value);
+	SetMMXRegister(X86_64_REGISTER_MM6, extended.fp_fxsave.mmx[6].value);
+	SetMMXRegister(X86_64_REGISTER_MM7, extended.fp_fxsave.mmx[7].value);
 
-	SetXMMRegister(X86_64_REGISTER_XMM0, extended.xmm_registers[0].value);
-	SetXMMRegister(X86_64_REGISTER_XMM1, extended.xmm_registers[1].value);
-	SetXMMRegister(X86_64_REGISTER_XMM2, extended.xmm_registers[2].value);
-	SetXMMRegister(X86_64_REGISTER_XMM3, extended.xmm_registers[3].value);
-	SetXMMRegister(X86_64_REGISTER_XMM4, extended.xmm_registers[4].value);
-	SetXMMRegister(X86_64_REGISTER_XMM5, extended.xmm_registers[5].value);
-	SetXMMRegister(X86_64_REGISTER_XMM6, extended.xmm_registers[6].value);
-	SetXMMRegister(X86_64_REGISTER_XMM7, extended.xmm_registers[7].value);
-	SetXMMRegister(X86_64_REGISTER_XMM8, extended.xmm_registers[8].value);
-	SetXMMRegister(X86_64_REGISTER_XMM9, extended.xmm_registers[9].value);
-	SetXMMRegister(X86_64_REGISTER_XMM10, extended.xmm_registers[10].value);
-	SetXMMRegister(X86_64_REGISTER_XMM11, extended.xmm_registers[11].value);
-	SetXMMRegister(X86_64_REGISTER_XMM12, extended.xmm_registers[12].value);
-	SetXMMRegister(X86_64_REGISTER_XMM13, extended.xmm_registers[13].value);
-	SetXMMRegister(X86_64_REGISTER_XMM14, extended.xmm_registers[14].value);
-	SetXMMRegister(X86_64_REGISTER_XMM15, extended.xmm_registers[15].value);
+	// The YMM register value is split in two halves in the saved CPU context,
+	// so we have to reassemble it here.
+	// TODO check extended.xstate_hdr to see if the YMM values are present at
+	// all.
+	SetXMMRegister(X86_64_REGISTER_XMM0, extended.fp_ymm[0].value,
+		extended.fp_fxsave.xmm[0].value);
+	SetXMMRegister(X86_64_REGISTER_XMM1, extended.fp_ymm[1].value,
+		extended.fp_fxsave.xmm[1].value);
+	SetXMMRegister(X86_64_REGISTER_XMM2, extended.fp_ymm[2].value,
+		extended.fp_fxsave.xmm[2].value);
+	SetXMMRegister(X86_64_REGISTER_XMM3, extended.fp_ymm[3].value,
+		extended.fp_fxsave.xmm[3].value);
+	SetXMMRegister(X86_64_REGISTER_XMM4, extended.fp_ymm[4].value,
+		extended.fp_fxsave.xmm[4].value);
+	SetXMMRegister(X86_64_REGISTER_XMM5, extended.fp_ymm[5].value,
+		extended.fp_fxsave.xmm[5].value);
+	SetXMMRegister(X86_64_REGISTER_XMM6, extended.fp_ymm[6].value,
+		extended.fp_fxsave.xmm[6].value);
+	SetXMMRegister(X86_64_REGISTER_XMM7, extended.fp_ymm[7].value,
+		extended.fp_fxsave.xmm[7].value);
+	SetXMMRegister(X86_64_REGISTER_XMM8, extended.fp_ymm[8].value,
+		extended.fp_fxsave.xmm[8].value);
+	SetXMMRegister(X86_64_REGISTER_XMM9, extended.fp_ymm[9].value,
+		extended.fp_fxsave.xmm[9].value);
+	SetXMMRegister(X86_64_REGISTER_XMM10, extended.fp_ymm[10].value,
+		extended.fp_fxsave.xmm[10].value);
+	SetXMMRegister(X86_64_REGISTER_XMM11, extended.fp_ymm[11].value,
+		extended.fp_fxsave.xmm[11].value);
+	SetXMMRegister(X86_64_REGISTER_XMM12, extended.fp_ymm[12].value,
+		extended.fp_fxsave.xmm[12].value);
+	SetXMMRegister(X86_64_REGISTER_XMM13, extended.fp_ymm[13].value,
+		extended.fp_fxsave.xmm[13].value);
+	SetXMMRegister(X86_64_REGISTER_XMM14, extended.fp_ymm[14].value,
+		extended.fp_fxsave.xmm[14].value);
+	SetXMMRegister(X86_64_REGISTER_XMM15, extended.fp_ymm[15].value,
+		extended.fp_fxsave.xmm[15].value);
 
 	fInterruptVector = state.vector;
 }
@@ -160,21 +180,21 @@ CpuStateX8664::UpdateDebugState(void* state, size_t size) const
 	x64State->ss = IntRegisterValue(X86_64_REGISTER_SS);
 
 	for (int32 i = 0; i < 8; i++) {
-		*(long double*)(x64State->extended_registers.fp_registers[i].value)
+		*(long double*)(x64State->extended_registers.fp_fxsave.fp[i].value)
 			= (long double)FloatRegisterValue(X86_64_REGISTER_ST0 + i);
 
 		if (IsRegisterSet(X86_64_REGISTER_MM0 + i)) {
-			memcpy(&x64State->extended_registers.mmx_registers[i],
+			memcpy(&x64State->extended_registers.fp_fxsave.mmx[i],
 				&fMMXRegisters[i], sizeof(x86_64_fp_register));
 		}
 	}
 
 	for (int32 i = 0; i < 16; i++) {
 		if (IsRegisterSet(X86_64_REGISTER_XMM0 + i)) {
-			memcpy(&x64State->extended_registers.xmm_registers[i],
+			memcpy(&x64State->extended_registers.fp_fxsave.xmm[i],
 				&fXMMRegisters[i], sizeof(x86_64_xmm_register));
 		} else {
-			memset(&x64State->extended_registers.xmm_registers[i],
+			memset(&x64State->extended_registers.fp_fxsave.xmm[i],
 				0, sizeof(x86_64_xmm_register));
 		}
 	}
@@ -372,12 +392,14 @@ CpuStateX8664::XMMRegisterValue(int32 index) const
 
 
 void
-CpuStateX8664::SetXMMRegister(int32 index, const uint8* value)
+CpuStateX8664::SetXMMRegister(int32 index, const uint8* highValue, const uint8* lowValue)
 {
 	if (index < X86_64_REGISTER_XMM0 || index >= X86_64_XMM_REGISTER_END)
 		return;
 
-	memcpy(fXMMRegisters[index - X86_64_REGISTER_XMM0].value, value,
+	memcpy(&fXMMRegisters[index - X86_64_REGISTER_XMM0].value[0], lowValue,
+		sizeof(x86_64_xmm_register));
+	memcpy(&fXMMRegisters[index - X86_64_REGISTER_XMM0].value[2], highValue,
 		sizeof(x86_64_xmm_register));
 	fSetRegisters[index] = 1;
 }
diff --git a/src/kits/debugger/arch/x86_64/CpuStateX8664.h b/src/kits/debugger/arch/x86_64/CpuStateX8664.h
index da7ca8aa0f..8e4c83721b 100644
--- a/src/kits/debugger/arch/x86_64/CpuStateX8664.h
+++ b/src/kits/debugger/arch/x86_64/CpuStateX8664.h
@@ -99,6 +99,11 @@ enum {
 	- X86_64_MMX_REGISTER_END)
 
 
+struct x86_64_ymm_register {
+	unsigned long value[4];
+};
+
+
 class CpuStateX8664 : public CpuState {
 public:
 								CpuStateX8664();
@@ -128,6 +133,7 @@ public:
 			uint64				IntRegisterValue(int32 index) const;
 			void				SetIntRegister(int32 index, uint64 value);
 
+private:
 			double				FloatRegisterValue(int32 index) const;
 			void				SetFloatRegister(int32 index, double value);
 
@@ -137,7 +143,7 @@ public:
 
 			const void*			XMMRegisterValue(int32 index) const;
 			void				SetXMMRegister(int32 index,
-									const uint8* value);
+									const uint8* highValue, const uint8* lowValue);
 
 			void				UnsetRegister(int32 index);
 
@@ -148,7 +154,7 @@ private:
 			uint64				fIntRegisters[X86_64_INT_REGISTER_COUNT];
 			double				fFloatRegisters[X86_64_FP_REGISTER_COUNT];
 			x86_64_fp_register	fMMXRegisters[X86_64_MMX_REGISTER_COUNT];
-			x86_64_xmm_register	fXMMRegisters[X86_64_XMM_REGISTER_COUNT];
+			x86_64_ymm_register	fXMMRegisters[X86_64_XMM_REGISTER_COUNT];
 			RegisterBitSet		fSetRegisters;
 			uint64				fInterruptVector;
 };
diff --git a/src/system/kernel/arch/x86/arch_user_debugger.cpp b/src/system/kernel/arch/x86/arch_user_debugger.cpp
index 952c091924..f1d8dcc6b0 100644
--- a/src/system/kernel/arch/x86/arch_user_debugger.cpp
+++ b/src/system/kernel/arch/x86/arch_user_debugger.cpp
@@ -33,7 +33,9 @@
 	// TODO: Make those real error codes.
 
 
-#ifndef __x86_64__
+#ifdef __x86_64__
+extern bool gHasXsave;
+#else
 extern bool gHasSSE;
 #endif
 
@@ -202,12 +204,21 @@ get_cpu_state(Thread* thread, iframe* frame, debug_cpu_state* cpuState)
 	// For the floating point state to be correct the calling function must
 	// not use these registers (not even indirectly).
 #ifdef __x86_64__
+	memset(&cpuState->extended_registers, 0,
+		sizeof(cpuState->extended_registers));
+
 	if (frame->fpu != nullptr) {
-		memcpy(&cpuState->extended_registers, frame->fpu,
-			sizeof(cpuState->extended_registers));
-	} else {
-		memset(&cpuState->extended_registers, 0,
-			sizeof(cpuState->extended_registers));
+		if (gHasXsave) {
+			// TODO check the xsave header to know the actual size of the
+			// register context depending on what is saved. For now we assume
+			// there is only the YMM AVX registers
+			memcpy(&cpuState->extended_registers, frame->fpu,
+				sizeof(cpuState->extended_registers));
+		} else {
+			// Only the "legacy area" saved by fxsave is available
+			memcpy(&cpuState->extended_registers, frame->fpu,
+				sizeof(cpuState->extended_registers.fp_fxsave));
+		}
 	}
 #else
 	Thread* thisThread = thread_get_current_thread();