diff --git a/include/cpu.h b/include/cpu.h
index 06d03589..5544f93f 100644
--- a/include/cpu.h
+++ b/include/cpu.h
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2002-2007  The DOSBox Team
+ *  Copyright (C) 2002-2008  The DOSBox Team
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -16,7 +16,7 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/* $Id: cpu.h,v 1.52 2008-01-16 20:16:31 c2woody Exp $ */
+/* $Id: cpu.h,v 1.53 2008-05-18 13:10:42 c2woody Exp $ */
 
 #ifndef DOSBOX_CPU_H
 #define DOSBOX_CPU_H
@@ -40,6 +40,14 @@
 
 #define CPU_CYCLES_LOWER_LIMIT		100
 
+
+#define CPU_ARCHTYPE_MIXED			0xff
+#define CPU_ARCHTYPE_386SLOW		0x30
+#define CPU_ARCHTYPE_386FAST		0x35
+#define CPU_ARCHTYPE_486OLDSLOW		0x40
+#define CPU_ARCHTYPE_486NEWSLOW		0x45
+#define CPU_ARCHTYPE_PENTIUMSLOW	0x50
+
 /* CPU Cycle Timing */
 extern Bit32s CPU_Cycles;
 extern Bit32s CPU_CycleLeft;
@@ -52,6 +60,8 @@ extern bool CPU_CycleAutoAdjust;
 extern bool CPU_SkipCycleAutoAdjust;
 extern Bitu CPU_AutoDetermineMode;
 
+extern Bitu CPU_ArchitectureType;
+
 /* Some common Defines */
 /* A CPU Handler */
 typedef Bits (CPU_Decoder)(void);
@@ -146,7 +156,7 @@ void CPU_Exception(Bitu which,Bitu error=0);
 bool CPU_SetSegGeneral(SegNames seg,Bitu value);
 bool CPU_PopSeg(SegNames seg,bool use32);
 
-void CPU_CPUID(void);
+bool CPU_CPUID(void);
 Bitu CPU_Pop16(void);
 Bitu CPU_Pop32(void);
 void CPU_Push16(Bitu value);
diff --git a/src/cpu/core_dyn_x86/decoder.h b/src/cpu/core_dyn_x86/decoder.h
index 4f23c0ad..56ebfb52 100644
--- a/src/cpu/core_dyn_x86/decoder.h
+++ b/src/cpu/core_dyn_x86/decoder.h
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2002-2007  The DOSBox Team
+ *  Copyright (C) 2002-2008  The DOSBox Team
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -16,6 +16,8 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+/* $Id: decoder.h,v 1.55 2008-05-18 13:11:14 c2woody Exp $ */
+
 #define X86_DYNFPU_DH_ENABLED
 #define X86_INLINED_MEMACCESS
 
@@ -1329,6 +1331,68 @@ static void dyn_mov_ev_gw(bool sign) {
 	}
 }
 
+static void dyn_cmpxchg_evgv(void) {
+	dyn_get_modrm();
+	DynReg * rm_reg=&DynRegs[decode.modrm.reg];
+	gen_protectflags();
+	if (decode.modrm.mod<3) {
+		gen_releasereg(DREG(EAX));
+		gen_releasereg(DREG(TMPB));
+		gen_releasereg(rm_reg);
+
+		dyn_fill_ea();
+		dyn_read_word(DREG(EA),DREG(TMPB),decode.big_op);
+		gen_dop_word(DOP_CMP,decode.big_op,DREG(EAX),DREG(TMPB));
+		Bit8u * branch=gen_create_branch(BR_NZ);
+
+		// eax==mem -> mem:=rm_reg
+		dyn_write_word_release(DREG(EA),rm_reg,decode.big_op);
+		gen_setzeroflag();
+		gen_releasereg(DREG(EAX));
+		gen_releasereg(DREG(TMPB));
+		gen_releasereg(rm_reg);
+
+		Bit8u * jump=gen_create_jump();
+
+		gen_fill_branch(branch);
+		// eax!=mem -> eax:=mem
+		dyn_write_word_release(DREG(EA),DREG(TMPB),decode.big_op);	// cmpxchg always issues write
+		gen_dop_word(DOP_MOV,decode.big_op,DREG(EAX),DREG(TMPB));
+		gen_clearzeroflag();
+		gen_releasereg(DREG(EAX));
+		gen_releasereg(DREG(TMPB));
+		gen_releasereg(rm_reg);
+
+		gen_fill_jump(jump);
+	} else {
+		gen_releasereg(DREG(EAX));
+		gen_releasereg(&DynRegs[decode.modrm.rm]);
+		gen_releasereg(rm_reg);
+
+		gen_dop_word(DOP_CMP,decode.big_op,DREG(EAX),&DynRegs[decode.modrm.rm]);
+		Bit8u * branch=gen_create_branch(BR_NZ);
+
+		// eax==rm -> rm:=rm_reg
+		gen_dop_word(DOP_MOV,decode.big_op,&DynRegs[decode.modrm.rm],rm_reg);
+		gen_setzeroflag();
+		gen_releasereg(DREG(EAX));
+		gen_releasereg(&DynRegs[decode.modrm.rm]);
+		gen_releasereg(rm_reg);
+
+		Bit8u * jump=gen_create_jump();
+
+		gen_fill_branch(branch);
+		// eax!=rm -> eax:=rm
+		gen_dop_word(DOP_MOV,decode.big_op,DREG(EAX),&DynRegs[decode.modrm.rm]);
+		gen_clearzeroflag();
+		gen_releasereg(DREG(EAX));
+		gen_releasereg(&DynRegs[decode.modrm.rm]);
+		gen_releasereg(rm_reg);
+
+		gen_fill_jump(jump);
+	}
+}
+
 static void dyn_dshift_ev_gv(bool left,bool immediate) {
 	dyn_get_modrm();
 	DynReg * rm_reg=&DynRegs[decode.modrm.reg];
@@ -1995,6 +2059,8 @@ restart_prefix:
 			case 0xad:dyn_dshift_ev_gv(false,false);break;		
 			/* Imul Ev,Gv */
 			case 0xaf:dyn_imul_gvev(0);break;
+			/* CMPXCHG */
+			case 0xb1:dyn_cmpxchg_evgv();break;
 			/* LFS,LGS */
 			case 0xb4:
 				dyn_get_modrm();
diff --git a/src/cpu/core_dyn_x86/risc_x86.h b/src/cpu/core_dyn_x86/risc_x86.h
index 709cf6b6..b091c384 100644
--- a/src/cpu/core_dyn_x86/risc_x86.h
+++ b/src/cpu/core_dyn_x86/risc_x86.h
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2002-2007  The DOSBox Team
+ *  Copyright (C) 2002-2008  The DOSBox Team
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -16,6 +16,8 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+/* $Id: risc_x86.h,v 1.30 2008-05-18 13:11:14 c2woody Exp $ */
+
 static void gen_init(void);
 
 /* End of needed */
@@ -268,6 +270,18 @@ static void gen_needcarry(void) {
 	}
 }
 
+static void gen_setzeroflag(void) {
+	if (x86gen.flagsactive) IllegalOption("gen_setzeroflag");
+	cache_addw(0x0c83);			//OR DWORD [ESP],0x40
+	cache_addw(0x4024);
+}
+
+static void gen_clearzeroflag(void) {
+	if (x86gen.flagsactive) IllegalOption("gen_clearzeroflag");
+	cache_addw(0x2483);			//AND DWORD [ESP],~0x40
+	cache_addw(0xbf24);
+}
+
 static bool skip_flags=false;
 
 static void set_skipflags(bool state) {
diff --git a/src/cpu/core_full/load.h b/src/cpu/core_full/load.h
index a0c1ca47..a5e7adeb 100644
--- a/src/cpu/core_full/load.h
+++ b/src/cpu/core_full/load.h
@@ -468,7 +468,7 @@ l_M_Ed:
 		AAS();
 		goto nextopcode;
 	case D_CPUID:
-		CPU_CPUID();
+		if (!CPU_CPUID()) goto illegalopcode;
 		goto nextopcode;
 	case D_HLT:
 		if (cpu.pmode && cpu.cpl) EXCEPTION(EXCEPTION_GP);
diff --git a/src/cpu/core_full/op.h b/src/cpu/core_full/op.h
index 67ae2c9a..bfcb90d1 100644
--- a/src/cpu/core_full/op.h
+++ b/src/cpu/core_full/op.h
@@ -585,8 +585,22 @@ switch (inst.code.op) {
 		inst_op1_d&=~(1 << (inst_op2_d & 31));
 		break;
 	case O_BSWAP:
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegalopcode;
 		BSWAP(inst_op1_d);
 		break;
+	case O_CMPXCHG:
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486NEWSLOW) goto illegalopcode;
+		FillFlags();
+		if (inst_op1_d==reg_eax) {
+			inst_op1_d=reg_32(inst.rm_index);
+			if (inst.rm<0xc0) SaveMd(inst.rm_eaa,inst_op1_d);	// early write-pf
+			SETFLAGBIT(ZF,1);
+		} else {
+			if (inst.rm<0xc0) SaveMd(inst.rm_eaa,inst_op1_d);	// early write-pf
+			reg_eax=inst_op1_d;
+			SETFLAGBIT(ZF,0);
+		}
+		break;
 	case O_FPU:
 #if C_FPU
 		switch (((inst.rm>=0xc0) << 3) | inst.code.save) {
diff --git a/src/cpu/core_full/optable.h b/src/cpu/core_full/optable.h
index fcdb1508..39907e0e 100644
--- a/src/cpu/core_full/optable.h
+++ b/src/cpu/core_full/optable.h
@@ -661,7 +661,7 @@ static OpCode OpCodeTable[1024]={
 {0			,0			,0		,0		},{L_MODRM	,O_IMULRd	,S_Gd	,M_EdxGdx	},
 
 /* 0x3b0 - 0x3b7 */
-{0			,0			,0		,0		},{0		,0			,0		,0		},
+{0			,0			,0		,0		},{L_MODRM	,O_CMPXCHG	,S_Ed	,M_Ed	},
 {L_MODRM	,O_SEGSS	,S_SEGGd,M_Efd	},{L_MODRM	,O_BTRd		,S_Ed	,M_EdGdt	},
 {L_MODRM	,O_SEGFS	,S_SEGGd,M_Efd	},{L_MODRM	,O_SEGGS	,S_SEGGd,M_Efd	},
 {L_MODRM	,0			,S_Gd	,M_Eb	},{L_MODRM	,0			,S_Gd	,M_Ew	},
diff --git a/src/cpu/core_full/support.h b/src/cpu/core_full/support.h
index cde08ebc..32b92620 100644
--- a/src/cpu/core_full/support.h
+++ b/src/cpu/core_full/support.h
@@ -94,7 +94,7 @@ enum {
 	O_BTd,O_BTSd,O_BTRd,O_BTCd,
 	O_BSFw,O_BSRw,O_BSFd,O_BSRd,
 
-	O_BSWAP,
+	O_BSWAP,O_CMPXCHG,
 	O_FPU,
 
 
diff --git a/src/cpu/core_normal/prefix_0f.h b/src/cpu/core_normal/prefix_0f.h
index 16397144..388c15c2 100644
--- a/src/cpu/core_normal/prefix_0f.h
+++ b/src/cpu/core_normal/prefix_0f.h
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2002-2007  The DOSBox Team
+ *  Copyright (C) 2002-2008  The DOSBox Team
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -142,6 +142,11 @@
 		if (cpu.pmode && cpu.cpl) EXCEPTION(EXCEPTION_GP);
 		cpu.cr0&=(~CR0_TASKSWITCH);
 		break;
+	CASE_0F_B(0x08)												/* INVD */
+	CASE_0F_B(0x09)												/* WBINVD */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
+		if (cpu.pmode && cpu.cpl) EXCEPTION(EXCEPTION_GP);
+		break;
 	CASE_0F_B(0x20)												/* MOV Rd.CRx */
 		{
 			GetRM;
@@ -220,6 +225,14 @@
 			if (CPU_WRITE_TRX(which,*eard)) RUNEXCEPTION();
 		}
 		break;
+	CASE_0F_B(0x31)												/* RDTSC */
+		{
+			if (CPU_ArchitectureType<CPU_ARCHTYPE_PENTIUMSLOW) goto illegal_opcode;
+			Bit64s tsc=(Bit64s)(PIC_FullIndex()*(double)CPU_CycleMax);
+			reg_edx=(Bit32u)(tsc>>32);
+			reg_eax=(Bit32u)(tsc&0xffffffff);
+		}
+		break;
 	CASE_0F_W(0x80)												/* JO */
 		JumpCond16_w(TFLG_O);break;
 	CASE_0F_W(0x81)												/* JNO */
@@ -291,7 +304,8 @@
 		if (CPU_PopSeg(fs,false)) RUNEXCEPTION();
 		break;
 	CASE_0F_B(0xa2)												/* CPUID */
-		CPU_CPUID();break;
+		if (!CPU_CPUID()) goto illegal_opcode;
+		break;
 	CASE_0F_W(0xa3)												/* BT Ew,Gw */
 		{
 			FillFlags();GetRMrw;
@@ -503,6 +517,7 @@
 		}
 	CASE_0F_B(0xc0)												/* XADD Gb,Eb */
 		{
+			if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 			GetRMrb;Bit8u oldrmrb=*rmrb;
 			if (rm >= 0xc0 ) {GetEArb;*rmrb=*earb;*earb+=oldrmrb;}
 			else {GetEAa;*rmrb=LoadMb(eaa);SaveMb(eaa,LoadMb(eaa)+oldrmrb);}
@@ -510,25 +525,34 @@
 		}
 	CASE_0F_W(0xc1)												/* XADD Gw,Ew */
 		{
+			if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 			GetRMrw;Bit16u oldrmrw=*rmrw;
 			if (rm >= 0xc0 ) {GetEArw;*rmrw=*earw;*earw+=oldrmrw;}
 			else {GetEAa;*rmrw=LoadMw(eaa);SaveMw(eaa,LoadMw(eaa)+oldrmrw);}
 			break;
 		}
 	CASE_0F_B(0xc8)												/* BSWAP EAX */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_eax);break;
 	CASE_0F_B(0xc9)												/* BSWAP ECX */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_ecx);break;
 	CASE_0F_B(0xca)												/* BSWAP EDX */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_edx);break;
 	CASE_0F_B(0xcb)												/* BSWAP EBX */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_ebx);break;
 	CASE_0F_B(0xcc)												/* BSWAP ESP */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_esp);break;
 	CASE_0F_B(0xcd)												/* BSWAP EBP */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_ebp);break;
 	CASE_0F_B(0xce)												/* BSWAP ESI */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_esi);break;
 	CASE_0F_B(0xcf)												/* BSWAP EDI */
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 		BSWAP(reg_edi);break;
 		
diff --git a/src/cpu/core_normal/prefix_66_0f.h b/src/cpu/core_normal/prefix_66_0f.h
index 6c5318cd..fefbbee7 100644
--- a/src/cpu/core_normal/prefix_66_0f.h
+++ b/src/cpu/core_normal/prefix_66_0f.h
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2002-2007  The DOSBox Team
+ *  Copyright (C) 2002-2008  The DOSBox Team
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -235,6 +235,34 @@
 			RMGdEdOp3(DIMULD,*rmrd);
 			break;
 		}
+	CASE_0F_D(0xb1)												/* CMPXCHG Ed,Gd */
+		{	
+			if (CPU_ArchitectureType<CPU_ARCHTYPE_486NEWSLOW) goto illegal_opcode;
+			FillFlags();
+			GetRMrd;
+			if (rm >= 0xc0) {
+				GetEArd;
+				if (*eard==reg_eax) {
+					*eard=*rmrd;
+					SETFLAGBIT(ZF,1);
+				} else {
+					reg_eax=*eard;
+					SETFLAGBIT(ZF,0);
+				}
+			} else {
+				GetEAa;
+				Bit32u val=LoadMd(eaa);
+				if (val==reg_eax) {
+					SaveMd(eaa,*rmrd);
+					SETFLAGBIT(ZF,1);
+				} else {
+					SaveMd(eaa,val);
+					reg_eax=val;
+					SETFLAGBIT(ZF,0);
+				}
+			}
+			break;
+		}
 	CASE_0F_D(0xb2)												/* LSS Ed */
 		{	
 			GetRMrd;
@@ -405,6 +433,7 @@
 		}
 	CASE_0F_D(0xc1)												/* XADD Gd,Ed */
 		{
+			if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) goto illegal_opcode;
 			GetRMrd;Bit32u oldrmrd=*rmrd;
 			if (rm >= 0xc0 ) {GetEArd;*rmrd=*eard;*eard+=oldrmrd;}
 			else {GetEAa;*rmrd=LoadMd(eaa);SaveMd(eaa,LoadMd(eaa)+oldrmrd);}
diff --git a/src/cpu/cpu.cpp b/src/cpu/cpu.cpp
index 2fa38733..e5c8991a 100644
--- a/src/cpu/cpu.cpp
+++ b/src/cpu/cpu.cpp
@@ -16,7 +16,7 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/* $Id: cpu.cpp,v 1.110 2008-05-05 13:29:04 qbix79 Exp $ */
+/* $Id: cpu.cpp,v 1.111 2008-05-18 13:11:14 c2woody Exp $ */
 
 #include <assert.h>
 #include <sstream>
@@ -61,6 +61,10 @@ bool CPU_CycleAutoAdjust = false;
 bool CPU_SkipCycleAutoAdjust = false;
 Bitu CPU_AutoDetermineMode = 0;
 
+Bitu CPU_ArchitectureType = CPU_ARCHTYPE_MIXED;
+
+Bitu CPU_flag_id_toggle=0;
+
 void CPU_Core_Full_Init(void);
 void CPU_Core_Normal_Init(void);
 void CPU_Core_Simple_Init(void);
@@ -161,8 +165,10 @@ PhysPt SelBase(Bitu sel) {
 	}
 }
 
+
 void CPU_SetFlags(Bitu word,Bitu mask) {
-	reg_flags=(reg_flags & ~mask)|(word & mask)|2|FLAG_ID;
+	mask|=CPU_flag_id_toggle;	// ID-flag can be toggled on cpuid-supporting CPUs
+	reg_flags=(reg_flags & ~mask)|(word & mask)|2;
 	cpu.direction=1-((reg_flags & FLAG_DF) >> 9);
 }
 
@@ -1569,6 +1575,9 @@ bool CPU_WRITE_CRX(Bitu cr,Bitu value) {
 	/* Check if privileged to access control registers */
 	if (cpu.pmode && (cpu.cpl>0)) return CPU_PrepareException(EXCEPTION_GP,0);
 	if ((cr==1) || (cr>4)) return CPU_PrepareException(EXCEPTION_UD,0);
+	if (CPU_ArchitectureType<CPU_ARCHTYPE_486OLDSLOW) {
+		if (cr==4) return CPU_PrepareException(EXCEPTION_UD,0);
+	}
 	CPU_SET_CRX(cr,value);
 	return false;
 }
@@ -1576,7 +1585,9 @@ bool CPU_WRITE_CRX(Bitu cr,Bitu value) {
 Bitu CPU_GET_CRX(Bitu cr) {
 	switch (cr) {
 	case 0:
-		return cpu.cr0;
+		if (CPU_ArchitectureType>=CPU_ARCHTYPE_PENTIUMSLOW) return cpu.cr0;
+		else if (CPU_ArchitectureType>=CPU_ARCHTYPE_486OLDSLOW) return (cpu.cr0 & 0xe005003f);
+		else return (cpu.cr0 | 0x7ffffff0);
 	case 2:
 		return paging.cr2;
 	case 3:
@@ -1613,7 +1624,11 @@ bool CPU_WRITE_DRX(Bitu dr,Bitu value) {
 		break;
 	case 5:
 	case 7:
-		cpu.drx[7]=(value|0x400) & 0xffff2fff;
+		if (CPU_ArchitectureType<CPU_ARCHTYPE_PENTIUMSLOW) {
+			cpu.drx[7]=(value|0x400) & 0xffff2fff;
+		} else {
+			cpu.drx[7]=(value|0x400);
+		}
 		break;
 	default:
 		LOG(LOG_CPU,LOG_ERROR)("Unhandled MOV DR%d,%X",dr,value);
@@ -1961,7 +1976,8 @@ bool CPU_PopSeg(SegNames seg,bool use32) {
 	return false;
 }
 
-void CPU_CPUID(void) {
+bool CPU_CPUID(void) {
+	if (CPU_ArchitectureType<CPU_ARCHTYPE_486NEWSLOW) return false;
 	switch (reg_eax) {
 	case 0:	/* Vendor ID String and maximum level? */
 		reg_eax=1;  /* Maximum level */ 
@@ -1970,15 +1986,30 @@ void CPU_CPUID(void) {
 		reg_ecx='n' | ('t' << 8) | ('e' << 16) | ('l'<< 24); 
 		break;
 	case 1:	/* get processor type/family/model/stepping and feature flags */
-		reg_eax=0x402;		/* intel 486 sx? */
-		reg_ebx=0;			/* Not Supported */
-		reg_ecx=0;			/* No features */
-		reg_edx=1;			/* FPU */
+		if ((CPU_ArchitectureType==CPU_ARCHTYPE_486NEWSLOW) ||
+			(CPU_ArchitectureType==CPU_ARCHTYPE_MIXED)) {
+			reg_eax=0x402;		/* intel 486dx */
+			reg_ebx=0;			/* Not Supported */
+			reg_ecx=0;			/* No features */
+			reg_edx=0x00000001;	/* FPU */
+		} else if (CPU_ArchitectureType==CPU_ARCHTYPE_PENTIUMSLOW) {
+			reg_eax=0x513;		/* intel pentium */
+			reg_ebx=0;			/* Not Supported */
+			reg_ecx=0;			/* No features */
+			reg_edx=0x00000011;	/* FPU+TimeStamp/RDTSC */
+		} else {
+			return false;
+		}
 		break;
 	default:
 		LOG(LOG_CPU,LOG_ERROR)("Unhandled CPUID Function %x",reg_eax);
+		reg_eax=0;
+		reg_ebx=0;
+		reg_ecx=0;
+		reg_edx=0;
 		break;
 	}
+	return true;
 }
 
 static Bits HLT_Decode(void) {
@@ -2140,7 +2171,11 @@ public:
 			cpu.drx[i]=0;
 			cpu.trx[i]=0;
 		}
-		cpu.drx[6]=0xffff1ff0;
+		if (CPU_ArchitectureType==CPU_ARCHTYPE_PENTIUMSLOW) {
+			cpu.drx[6]=0xffff0ff0;
+		} else {
+			cpu.drx[6]=0xffff1ff0;
+		}
 		cpu.drx[7]=0x00000400;
 
 		/* Init the cpu cores */
@@ -2237,7 +2272,7 @@ public:
 
 		CPU_CycleUp=section->Get_int("cycleup");
 		CPU_CycleDown=section->Get_int("cycledown");
-	        std::string core(section->Get_string("core"));
+		std::string core(section->Get_string("core"));
 		cpudecoder=&CPU_Core_Normal_Run;
 		if (core == "normal") {
 			cpudecoder=&CPU_Core_Normal_Run;
@@ -2271,7 +2306,25 @@ public:
 #elif (C_DYNREC)
 		CPU_Core_Dynrec_Cache_Init( core == "dynamic" );
 #endif
-	
+
+		CPU_ArchitectureType = CPU_ARCHTYPE_MIXED;
+		std::string cputype(section->Get_string("cputype"));
+		if (cputype == "auto") {
+			CPU_ArchitectureType = CPU_ARCHTYPE_MIXED;
+		} else if (cputype == "386") {
+			CPU_ArchitectureType = CPU_ARCHTYPE_386FAST;
+		} else if (cputype == "386_slow") {
+			CPU_ArchitectureType = CPU_ARCHTYPE_386SLOW;
+		} else if (cputype == "486_slow") {
+			CPU_ArchitectureType = CPU_ARCHTYPE_486NEWSLOW;
+		} else if (cputype == "pentium_slow") {
+			CPU_ArchitectureType = CPU_ARCHTYPE_PENTIUMSLOW;
+		}
+
+		if (CPU_ArchitectureType>=CPU_ARCHTYPE_486NEWSLOW) CPU_flag_id_toggle=FLAG_ID;
+		else CPU_flag_id_toggle=0;
+
+
 		if(CPU_CycleMax <= 0) CPU_CycleMax = 3000;
 		if(CPU_CycleUp <= 0)   CPU_CycleUp = 500;
 		if(CPU_CycleDown <= 0) CPU_CycleDown = 20;
diff --git a/src/cpu/paging.cpp b/src/cpu/paging.cpp
index fc7bfa85..7bbc97a6 100644
--- a/src/cpu/paging.cpp
+++ b/src/cpu/paging.cpp
@@ -16,7 +16,7 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/* $Id: paging.cpp,v 1.33 2008-01-05 21:05:06 c2woody Exp $ */
+/* $Id: paging.cpp,v 1.34 2008-05-18 13:11:14 c2woody Exp $ */
 
 #include <stdlib.h>
 #include <assert.h>
@@ -34,7 +34,6 @@
 #define LINK_TOTAL		(64*1024)
 
 #define USERWRITE_PROHIBITED			((cpu.cpl&cpu.mpl)==3)
-#define USERACCESS_PROHIBITED(u1,u2)	(((u1)==0) && ((u2)==0))
 
 
 PagingBlock paging;
@@ -228,6 +227,20 @@ static INLINE bool InitPageCheckPresence_CheckOnly(PhysPt lin_addr,bool writing,
 	return true;
 }
 
+static INLINE bool InitPage_CheckUseraccess(Bitu u1,Bitu u2) {
+	switch (CPU_ArchitectureType) {
+	case CPU_ARCHTYPE_MIXED:
+	case CPU_ARCHTYPE_386SLOW:
+	case CPU_ARCHTYPE_386FAST:
+	default:
+		return ((u1)==0) && ((u2)==0);
+	case CPU_ARCHTYPE_486OLDSLOW:
+	case CPU_ARCHTYPE_486NEWSLOW:
+	case CPU_ARCHTYPE_PENTIUMSLOW:
+		return ((u1)==0) || ((u2)==0);
+	}
+}
+
 
 class InitPageHandler : public PageHandler {
 public:
@@ -316,12 +329,40 @@ public:
 			// 2: can (but currently does not) fail a write privilege check
 			// 3: fails a privilege check
 			Bitu priv_check=0;
-			if (USERACCESS_PROHIBITED(entry.block.us,table.block.us)) {
+			if (InitPage_CheckUseraccess(entry.block.us,table.block.us)) {
 				if ((cpu.cpl&cpu.mpl)==3) priv_check=3;
-				else priv_check=1;
+				else {
+					switch (CPU_ArchitectureType) {
+					case CPU_ARCHTYPE_MIXED:
+					case CPU_ARCHTYPE_386FAST:
+					default:
+//						priv_check=0;	// default
+						break;
+					case CPU_ARCHTYPE_386SLOW:
+					case CPU_ARCHTYPE_486OLDSLOW:
+					case CPU_ARCHTYPE_486NEWSLOW:
+					case CPU_ARCHTYPE_PENTIUMSLOW:
+						priv_check=1;
+						break;
+					}
+				}
 			}
 			if ((entry.block.wr==0) || (table.block.wr==0)) {
-				if (priv_check==0) priv_check=2;
+				if (priv_check==0) {
+					switch (CPU_ArchitectureType) {
+					case CPU_ARCHTYPE_MIXED:
+					case CPU_ARCHTYPE_386FAST:
+					default:
+//						priv_check=0;	// default
+						break;
+					case CPU_ARCHTYPE_386SLOW:
+					case CPU_ARCHTYPE_486OLDSLOW:
+					case CPU_ARCHTYPE_486NEWSLOW:
+					case CPU_ARCHTYPE_PENTIUMSLOW:
+						priv_check=2;
+						break;
+					}
+				}
 				if (writing && USERWRITE_PROHIBITED) priv_check=3;
 			}
 			if (priv_check==3) {
@@ -374,7 +415,7 @@ public:
 
 			if (!USERWRITE_PROHIBITED) return true;
 
-			if (USERACCESS_PROHIBITED(entry.block.us,table.block.us) ||
+			if (InitPage_CheckUseraccess(entry.block.us,table.block.us) ||
 					(((entry.block.wr==0) || (table.block.wr==0)) && writing)) {
 				LOG(LOG_PAGING,LOG_NORMAL)("Page access denied: cpl=%i, %x:%x:%x:%x",
 					cpu.cpl,entry.block.us,table.block.us,entry.block.wr,table.block.wr);
@@ -507,7 +548,7 @@ public:
 			X86PageEntry entry;
 			if (!InitPageCheckPresence_CheckOnly(lin_addr,true,table,entry)) return 0;
 
-			if (USERACCESS_PROHIBITED(entry.block.us,table.block.us) || (((entry.block.wr==0) || (table.block.wr==0)))) {
+			if (InitPage_CheckUseraccess(entry.block.us,table.block.us) || (((entry.block.wr==0) || (table.block.wr==0)))) {
 				LOG(LOG_PAGING,LOG_NORMAL)("Page access denied: cpl=%i, %x:%x:%x:%x",
 					cpu.cpl,entry.block.us,table.block.us,entry.block.wr,table.block.wr);
 				paging.cr2=lin_addr;
diff --git a/src/dosbox.cpp b/src/dosbox.cpp
index e3374a08..81975831 100644
--- a/src/dosbox.cpp
+++ b/src/dosbox.cpp
@@ -16,7 +16,7 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/* $Id: dosbox.cpp,v 1.135 2008-05-10 17:33:27 c2woody Exp $ */
+/* $Id: dosbox.cpp,v 1.136 2008-05-18 13:10:42 c2woody Exp $ */
 
 #include <stdlib.h>
 #include <stdarg.h>
@@ -393,6 +393,12 @@ void DOSBOX_Init(void) {
 	Pstring->Set_values(cores);
 	Pstring->Set_help("CPU Core used in emulation. auto will switch to dynamic if available and appropriate.");
 
+	const char* cputype_values[] = { "auto", "386", "386_slow", "486_slow", "pentium_slow", 0};
+	Pstring = secprop->Add_string("cputype",Property::Changeable::Always,"auto");
+	Pstring->Set_values(cputype_values);
+	Pstring->Set_help("CPU Type used in emulation. auto is the fastest choice.");
+
+
 	Pmulti_remain = secprop->Add_multiremain("cycles",Property::Changeable::Always," ");
 	Pmulti_remain->Set_help(
 		"Amount of instructions DOSBox tries to emulate each millisecond. Setting this value too high results in sound dropouts and lags. Cycles can be set in 3 ways:\n"