diff --git a/scripts/src/cpu.lua b/scripts/src/cpu.lua
index c9639d1d7a1..126d28ed524 100644
--- a/scripts/src/cpu.lua
+++ b/scripts/src/cpu.lua
@@ -1515,6 +1515,7 @@ if (CPUS["NEC"]~=null) then
 	files {
 		MAME_DIR .. "src/devices/cpu/nec/nec.cpp",
 		MAME_DIR .. "src/devices/cpu/nec/nec.h",
+		MAME_DIR .. "src/devices/cpu/nec/nec_common.h",
 		MAME_DIR .. "src/devices/cpu/nec/necea.h",
 		MAME_DIR .. "src/devices/cpu/nec/necinstr.h",
 		MAME_DIR .. "src/devices/cpu/nec/necinstr.hxx",
diff --git a/src/devices/cpu/nec/nec_common.h b/src/devices/cpu/nec/nec_common.h
new file mode 100644
index 00000000000..4356214a302
--- /dev/null
+++ b/src/devices/cpu/nec/nec_common.h
@@ -0,0 +1,9 @@
+#ifndef NEC_COMMON_H
+#define NEC_COMMON_H
+
+#include <stdint.h>
+
+extern int necv_dasm_one(std::ostream &stream, uint32_t eip, const uint8_t *oprom, const uint8_t *decryption_table);
+extern int necv_dasm_one(char *buffer, uint32_t eip, const uint8_t *oprom, const uint8_t *decryption_table);
+
+#endif // NEC_COMMON_H
diff --git a/src/devices/cpu/nec/necdasm.cpp b/src/devices/cpu/nec/necdasm.cpp
index 78e3badea8e..e3fdb36f94a 100644
--- a/src/devices/cpu/nec/necdasm.cpp
+++ b/src/devices/cpu/nec/necdasm.cpp
@@ -8,6 +8,7 @@
 */
 
 #include "emu.h"
+#include "nec_common.h"
 
 static const uint8_t *Iconfig;
 
@@ -985,10 +986,9 @@ static void handle_modrm(char* s)
 		disp16 = FETCHD16();
 		s += sprintf( s, "%s", shexstring((int32_t)disp16, 0, true) );
 	}
-	s += sprintf( s, "]" );
-}
+	s += sprintf( s, "]" );}
 
-static char* handle_param(char* s, uint32_t param)
+static void handle_param(std::ostream &stream, uint32_t param)
 {
 	uint8_t i8;
 	uint16_t i16;
@@ -1000,139 +1000,138 @@ static char* handle_param(char* s, uint32_t param)
 	switch(param)
 	{
 		case PARAM_REG8:
-			s += sprintf( s, "%s", nec_reg8[MODRM_REG1] );
+			util::stream_format( stream, "%s", nec_reg8[MODRM_REG1] );
 			break;
 
 		case PARAM_REG16:
-			s += sprintf( s, "%s", nec_reg[MODRM_REG1] );
+			util::stream_format( stream, "%s", nec_reg[MODRM_REG1] );
 			break;
 
 		case PARAM_REG2_8:
-			s += sprintf( s, "%s", nec_reg8[MODRM_REG2] );
+			util::stream_format( stream, "%s", nec_reg8[MODRM_REG2] );
 			break;
 
 		case PARAM_REG2_16:
-			s += sprintf( s, "%s", nec_reg[MODRM_REG2] );
+			util::stream_format( stream, "%s", nec_reg[MODRM_REG2] );
 			break;
 
 		case PARAM_RM8:
 		case PARAM_RMPTR8:
 			if( modrm >= 0xc0 ) {
-				s += sprintf( s, "%s", nec_reg8[MODRM_REG2] );
+				util::stream_format( stream, "%s", nec_reg8[MODRM_REG2] );
 			} else {
 				if (param == PARAM_RMPTR8)
-					s += sprintf( s, "byte ptr " );
-				s += sprintf( s, "%s", modrm_string );
+					util::stream_format( stream, "byte ptr " );
+				util::stream_format( stream, "%s", modrm_string );
 			}
 			break;
 
 		case PARAM_RM16:
 		case PARAM_RMPTR16:
 			if( modrm >= 0xc0 ) {
-				s += sprintf( s, "%s", nec_reg[MODRM_REG2] );
+				util::stream_format( stream, "%s", nec_reg[MODRM_REG2] );
 			} else {
 				if (param == PARAM_RMPTR16)
-					s += sprintf( s, "word ptr " );
-				s += sprintf( s, "%s", modrm_string );
+					util::stream_format( stream, "word ptr " );
+				util::stream_format( stream, "%s", modrm_string );
 			}
 			break;
 
 		case PARAM_I3:
 			i8 = FETCHD();
-			s += sprintf( s, "%d", i8 & 0x07 );
+			util::stream_format( stream, "%d", i8 & 0x07 );
 			break;
 
 		case PARAM_I4:
 			i8 = FETCHD();
-			s += sprintf( s, "%d", i8 & 0x0f );
+			util::stream_format( stream, "%d", i8 & 0x0f );
 			break;
 
 		case PARAM_I8:
 			i8 = FETCHD();
-			s += sprintf( s, "%s", shexstring((int8_t)i8, 0, false) );
+			util::stream_format( stream, "%s", shexstring((int8_t)i8, 0, false) );
 			break;
 
 		case PARAM_I16:
 			i16 = FETCHD16();
-			s += sprintf( s, "%s", shexstring((int16_t)i16, 0, false) );
+			util::stream_format( stream, "%s", shexstring((int16_t)i16, 0, false) );
 			break;
 
 		case PARAM_UI8:
 			i8 = FETCHD();
-			s += sprintf( s, "%s", shexstring((uint8_t)i8, 0, false) );
+			util::stream_format( stream, "%s", shexstring((uint8_t)i8, 0, false) );
 			break;
 
 		case PARAM_IMM:
 			i16 = FETCHD16();
-			s += sprintf( s, "%s", hexstring(i16, 0) );
+			util::stream_format( stream, "%s", hexstring(i16, 0) );
 			break;
 
 		case PARAM_ADDR:
 			addr = FETCHD16();
 			ptr = FETCHD16();
-			s += sprintf( s, "%s:", hexstring(ptr, 4) );
-			s += sprintf( s, "%s", hexstring(addr, 0) );
+			util::stream_format( stream, "%s:", hexstring(ptr, 4) );
+			util::stream_format( stream, "%s", hexstring(addr, 0) );
 			break;
 
 		case PARAM_REL16:
 			/* make sure to keep the relative offset within the segment */
 			d16 = FETCHD16();
-			s += sprintf( s, "%s", hexstring((pc & 0xFFFF0000) | ((pc + d16) & 0x0000FFFF), 0) );
+			util::stream_format( stream, "%s", hexstring((pc & 0xFFFF0000) | ((pc + d16) & 0x0000FFFF), 0) );
 			break;
 
 		case PARAM_REL8:
 			d8 = FETCHD();
-			s += sprintf( s, "%s", hexstring(pc + d8, 0) );
+			util::stream_format( stream, "%s", hexstring(pc + d8, 0) );
 			break;
 
 		case PARAM_MEM_OFFS:
 			switch(segment)
 			{
-				case SEG_PS: s += sprintf( s, "ps:" ); break;
-				case SEG_DS0: s += sprintf( s, "ds0:" ); break;
-				case SEG_DS1: s += sprintf( s, "ds1:" ); break;
-				case SEG_SS: s += sprintf( s, "ss:" ); break;
+				case SEG_PS: util::stream_format( stream, "ps:" ); break;
+				case SEG_DS0: util::stream_format( stream, "ds0:" ); break;
+				case SEG_DS1: util::stream_format( stream, "ds1:" ); break;
+				case SEG_SS: util::stream_format( stream, "ss:" ); break;
 			}
 
 			i16 = FETCHD16();
-			s += sprintf( s, "[%s]", hexstring(i16, 0) );
+			util::stream_format( stream, "[%s]", hexstring(i16, 0) );
 			break;
 
 		case PARAM_SREG:
-			s += sprintf( s, "%s", nec_sreg[MODRM_REG1] );
+			util::stream_format( stream, "%s", nec_sreg[MODRM_REG1] );
 			break;
 
 		case PARAM_SFREG:
 			i8 = FETCHD();
-			s += sprintf( s, "%s", nec_sfreg[i8] );
+			util::stream_format( stream, "%s", nec_sfreg[i8] );
 			break;
 
 		case PARAM_1:
-			s += sprintf( s, "1" );
+			util::stream_format( stream, "1" );
 			break;
 
-		case PARAM_AL: s += sprintf( s, "al" ); break;
-		case PARAM_CL: s += sprintf( s, "cl" ); break;
-		case PARAM_DL: s += sprintf( s, "dl" ); break;
-		case PARAM_BL: s += sprintf( s, "bl" ); break;
-		case PARAM_AH: s += sprintf( s, "ah" ); break;
-		case PARAM_CH: s += sprintf( s, "ch" ); break;
-		case PARAM_DH: s += sprintf( s, "dh" ); break;
-		case PARAM_BH: s += sprintf( s, "bh" ); break;
+		case PARAM_AL: util::stream_format( stream, "al" ); break;
+		case PARAM_CL: util::stream_format( stream, "cl" ); break;
+		case PARAM_DL: util::stream_format( stream, "dl" ); break;
+		case PARAM_BL: util::stream_format( stream, "bl" ); break;
+		case PARAM_AH: util::stream_format( stream, "ah" ); break;
+		case PARAM_CH: util::stream_format( stream, "ch" ); break;
+		case PARAM_DH: util::stream_format( stream, "dh" ); break;
+		case PARAM_BH: util::stream_format( stream, "bh" ); break;
 
-		case PARAM_AW: s += sprintf( s, "aw" ); break;
-		case PARAM_CW: s += sprintf( s, "cw" ); break;
-		case PARAM_DW: s += sprintf( s, "dw" ); break;
-		case PARAM_BW: s += sprintf( s, "bw" ); break;
-		case PARAM_SP: s += sprintf( s, "sp" ); break;
-		case PARAM_BP: s += sprintf( s, "bp" ); break;
-		case PARAM_IX: s += sprintf( s, "ix" ); break;
-		case PARAM_IY: s += sprintf( s, "iy" ); break;
+		case PARAM_AW: util::stream_format( stream, "aw" ); break;
+		case PARAM_CW: util::stream_format( stream, "cw" ); break;
+		case PARAM_DW: util::stream_format( stream, "dw" ); break;
+		case PARAM_BW: util::stream_format( stream, "bw" ); break;
+		case PARAM_SP: util::stream_format( stream, "sp" ); break;
+		case PARAM_BP: util::stream_format( stream, "bp" ); break;
+		case PARAM_IX: util::stream_format( stream, "ix" ); break;
+		case PARAM_IY: util::stream_format( stream, "iy" ); break;
 	}
-	return s;
 }
 
-static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
+static void handle_fpu(std::ostream &stream, uint8_t op1, uint8_t op2)
 {
 	switch (op1 & 0x7)
 	{
@@ -1145,28 +1144,28 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fadd    dword ptr %s", modrm_string); break;
-					case 1: sprintf(s, "fmul    dword ptr %s", modrm_string); break;
-					case 2: sprintf(s, "fcom    dword ptr %s", modrm_string); break;
-					case 3: sprintf(s, "fcomp   dword ptr %s", modrm_string); break;
-					case 4: sprintf(s, "fsub    dword ptr %s", modrm_string); break;
-					case 5: sprintf(s, "fsubr   dword ptr %s", modrm_string); break;
-					case 6: sprintf(s, "fdiv    dword ptr %s", modrm_string); break;
-					case 7: sprintf(s, "fdivr   dword ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fadd    dword ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "fmul    dword ptr %s", modrm_string); break;
+					case 2: util::stream_format(stream, "fcom    dword ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "fcomp   dword ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "fsub    dword ptr %s", modrm_string); break;
+					case 5: util::stream_format(stream, "fsubr   dword ptr %s", modrm_string); break;
+					case 6: util::stream_format(stream, "fdiv    dword ptr %s", modrm_string); break;
+					case 7: util::stream_format(stream, "fdivr   dword ptr %s", modrm_string); break;
 				}
 			}
 			else
 			{
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fadd    st(0),st(%d)", op2 & 0x7); break;
-					case 1: sprintf(s, "fcom    st(0),st(%d)", op2 & 0x7); break;
-					case 2: sprintf(s, "fsub    st(0),st(%d)", op2 & 0x7); break;
-					case 3: sprintf(s, "fdiv    st(0),st(%d)", op2 & 0x7); break;
-					case 4: sprintf(s, "fmul    st(0),st(%d)", op2 & 0x7); break;
-					case 5: sprintf(s, "fcomp   st(0),st(%d)", op2 & 0x7); break;
-					case 6: sprintf(s, "fsubr   st(0),st(%d)", op2 & 0x7); break;
-					case 7: sprintf(s, "fdivr   st(0),st(%d)", op2 & 0x7); break;
+					case 0: util::stream_format(stream, "fadd    st(0),st(%d)", op2 & 0x7); break;
+					case 1: util::stream_format(stream, "fcom    st(0),st(%d)", op2 & 0x7); break;
+					case 2: util::stream_format(stream, "fsub    st(0),st(%d)", op2 & 0x7); break;
+					case 3: util::stream_format(stream, "fdiv    st(0),st(%d)", op2 & 0x7); break;
+					case 4: util::stream_format(stream, "fmul    st(0),st(%d)", op2 & 0x7); break;
+					case 5: util::stream_format(stream, "fcomp   st(0),st(%d)", op2 & 0x7); break;
+					case 6: util::stream_format(stream, "fsubr   st(0),st(%d)", op2 & 0x7); break;
+					case 7: util::stream_format(stream, "fdivr   st(0),st(%d)", op2 & 0x7); break;
 				}
 			}
 			break;
@@ -1181,14 +1180,14 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fld     dword ptr %s", modrm_string); break;
-					case 1: sprintf(s, "??? (FPU)"); break;
-					case 2: sprintf(s, "fst     dword ptr %s", modrm_string); break;
-					case 3: sprintf(s, "fstp    dword ptr %s", modrm_string); break;
-					case 4: sprintf(s, "fldenv  word ptr %s", modrm_string); break;
-					case 5: sprintf(s, "fldcw   word ptr %s", modrm_string); break;
-					case 6: sprintf(s, "fstenv  word ptr %s", modrm_string); break;
-					case 7: sprintf(s, "fstcw   word ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fld     dword ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "??? (FPU)"); break;
+					case 2: util::stream_format(stream, "fst     dword ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "fstp    dword ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "fldenv  word ptr %s", modrm_string); break;
+					case 5: util::stream_format(stream, "fldcw   word ptr %s", modrm_string); break;
+					case 6: util::stream_format(stream, "fstenv  word ptr %s", modrm_string); break;
+					case 7: util::stream_format(stream, "fstcw   word ptr %s", modrm_string); break;
 				}
 			}
 			else
@@ -1196,41 +1195,41 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				switch (op2 & 0x3f)
 				{
 					case 0x00: case 0x01: case 0x02: case 0x03: case 0x04: case 0x05: case 0x06: case 0x07:
-						sprintf(s, "fld     st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fld     st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x08: case 0x09: case 0x0a: case 0x0b: case 0x0c: case 0x0d: case 0x0e: case 0x0f:
-						sprintf(s, "fxch    st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fxch    st(0),st(%d)", op2 & 0x7); break;
 
-					case 0x10: sprintf(s, "fnop"); break;
-					case 0x20: sprintf(s, "fchs"); break;
-					case 0x21: sprintf(s, "fabs"); break;
-					case 0x24: sprintf(s, "ftst"); break;
-					case 0x25: sprintf(s, "fxam"); break;
-					case 0x28: sprintf(s, "fld1"); break;
-					case 0x29: sprintf(s, "fldl2t"); break;
-					case 0x2a: sprintf(s, "fldl2e"); break;
-					case 0x2b: sprintf(s, "fldpi"); break;
-					case 0x2c: sprintf(s, "fldlg2"); break;
-					case 0x2d: sprintf(s, "fldln2"); break;
-					case 0x2e: sprintf(s, "fldz"); break;
-					case 0x30: sprintf(s, "f2xm1"); break;
-					case 0x31: sprintf(s, "fyl2x"); break;
-					case 0x32: sprintf(s, "fptan"); break;
-					case 0x33: sprintf(s, "fpatan"); break;
-					case 0x34: sprintf(s, "fxtract"); break;
-					case 0x35: sprintf(s, "fprem1"); break;
-					case 0x36: sprintf(s, "fdecstp"); break;
-					case 0x37: sprintf(s, "fincstp"); break;
-					case 0x38: sprintf(s, "fprem"); break;
-					case 0x39: sprintf(s, "fyl2xp1"); break;
-					case 0x3a: sprintf(s, "fsqrt"); break;
-					case 0x3b: sprintf(s, "fsincos"); break;
-					case 0x3c: sprintf(s, "frndint"); break;
-					case 0x3d: sprintf(s, "fscale"); break;
-					case 0x3e: sprintf(s, "fsin"); break;
-					case 0x3f: sprintf(s, "fcos"); break;
+					case 0x10: util::stream_format(stream, "fnop"); break;
+					case 0x20: util::stream_format(stream, "fchs"); break;
+					case 0x21: util::stream_format(stream, "fabs"); break;
+					case 0x24: util::stream_format(stream, "ftst"); break;
+					case 0x25: util::stream_format(stream, "fxam"); break;
+					case 0x28: util::stream_format(stream, "fld1"); break;
+					case 0x29: util::stream_format(stream, "fldl2t"); break;
+					case 0x2a: util::stream_format(stream, "fldl2e"); break;
+					case 0x2b: util::stream_format(stream, "fldpi"); break;
+					case 0x2c: util::stream_format(stream, "fldlg2"); break;
+					case 0x2d: util::stream_format(stream, "fldln2"); break;
+					case 0x2e: util::stream_format(stream, "fldz"); break;
+					case 0x30: util::stream_format(stream, "f2xm1"); break;
+					case 0x31: util::stream_format(stream, "fyl2x"); break;
+					case 0x32: util::stream_format(stream, "fptan"); break;
+					case 0x33: util::stream_format(stream, "fpatan"); break;
+					case 0x34: util::stream_format(stream, "fxtract"); break;
+					case 0x35: util::stream_format(stream, "fprem1"); break;
+					case 0x36: util::stream_format(stream, "fdecstp"); break;
+					case 0x37: util::stream_format(stream, "fincstp"); break;
+					case 0x38: util::stream_format(stream, "fprem"); break;
+					case 0x39: util::stream_format(stream, "fyl2xp1"); break;
+					case 0x3a: util::stream_format(stream, "fsqrt"); break;
+					case 0x3b: util::stream_format(stream, "fsincos"); break;
+					case 0x3c: util::stream_format(stream, "frndint"); break;
+					case 0x3d: util::stream_format(stream, "fscale"); break;
+					case 0x3e: util::stream_format(stream, "fsin"); break;
+					case 0x3f: util::stream_format(stream, "fcos"); break;
 
-					default: sprintf(s, "??? (FPU)"); break;
+					default: util::stream_format(stream, "??? (FPU)"); break;
 				}
 			}
 			break;
@@ -1245,14 +1244,14 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fiadd   dword ptr %s", modrm_string); break;
-					case 1: sprintf(s, "fimul   dword ptr %s", modrm_string); break;
-					case 2: sprintf(s, "ficom   dword ptr %s", modrm_string); break;
-					case 3: sprintf(s, "ficomp  dword ptr %s", modrm_string); break;
-					case 4: sprintf(s, "fisub   dword ptr %s", modrm_string); break;
-					case 5: sprintf(s, "fisubr  dword ptr %s", modrm_string); break;
-					case 6: sprintf(s, "fidiv   dword ptr %s", modrm_string); break;
-					case 7: sprintf(s, "fidivr  dword ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fiadd   dword ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "fimul   dword ptr %s", modrm_string); break;
+					case 2: util::stream_format(stream, "ficom   dword ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "ficomp  dword ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "fisub   dword ptr %s", modrm_string); break;
+					case 5: util::stream_format(stream, "fisubr  dword ptr %s", modrm_string); break;
+					case 6: util::stream_format(stream, "fidiv   dword ptr %s", modrm_string); break;
+					case 7: util::stream_format(stream, "fidivr  dword ptr %s", modrm_string); break;
 				}
 			}
 			else
@@ -1260,18 +1259,18 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				switch (op2 & 0x3f)
 				{
 					case 0x00: case 0x01: case 0x02: case 0x03: case 0x04: case 0x05: case 0x06: case 0x07:
-						sprintf(s, "fcmovb  st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmovb  st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x08: case 0x09: case 0x0a: case 0x0b: case 0x0c: case 0x0d: case 0x0e: case 0x0f:
-						sprintf(s, "fcmove  st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmove  st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x10: case 0x11: case 0x12: case 0x13: case 0x14: case 0x15: case 0x16: case 0x17:
-						sprintf(s, "fcmovbe st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmovbe st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x18: case 0x19: case 0x1a: case 0x1b: case 0x1c: case 0x1d: case 0x1e: case 0x1f:
-						sprintf(s, "fcmovu  st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmovu  st(0),st(%d)", op2 & 0x7); break;
 
-					default: sprintf(s, "??? (FPU)"); break;
+					default: util::stream_format(stream, "??? (FPU)"); break;
 
 				}
 			}
@@ -1287,14 +1286,14 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fild    dword ptr %s", modrm_string); break;
-					case 1: sprintf(s, "??? (FPU)"); break;
-					case 2: sprintf(s, "fist    dword ptr %s", modrm_string); break;
-					case 3: sprintf(s, "fistp   dword ptr %s", modrm_string); break;
-					case 4: sprintf(s, "??? (FPU)"); break;
-					case 5: sprintf(s, "fld     tword ptr %s", modrm_string); break;
-					case 6: sprintf(s, "??? (FPU)"); break;
-					case 7: sprintf(s, "fstp    tword ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fild    dword ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "??? (FPU)"); break;
+					case 2: util::stream_format(stream, "fist    dword ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "fistp   dword ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "??? (FPU)"); break;
+					case 5: util::stream_format(stream, "fld     tword ptr %s", modrm_string); break;
+					case 6: util::stream_format(stream, "??? (FPU)"); break;
+					case 7: util::stream_format(stream, "fstp    tword ptr %s", modrm_string); break;
 				}
 			}
 			else
@@ -1302,27 +1301,27 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				switch (op2 & 0x3f)
 				{
 					case 0x00: case 0x01: case 0x02: case 0x03: case 0x04: case 0x05: case 0x06: case 0x07:
-						sprintf(s, "fcmovnb st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmovnb st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x08: case 0x09: case 0x0a: case 0x0b: case 0x0c: case 0x0d: case 0x0e: case 0x0f:
-						sprintf(s, "fcmovne st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmovne st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x10: case 0x11: case 0x12: case 0x13: case 0x14: case 0x15: case 0x16: case 0x17:
-						sprintf(s, "fcmovnbe st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmovnbe st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x18: case 0x19: case 0x1a: case 0x1b: case 0x1c: case 0x1d: case 0x1e: case 0x1f:
-						sprintf(s, "fcmovnu st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcmovnu st(0),st(%d)", op2 & 0x7); break;
 
-					case 0x22: sprintf(s, "fclex"); break;
-					case 0x23: sprintf(s, "finit"); break;
+					case 0x22: util::stream_format(stream, "fclex"); break;
+					case 0x23: util::stream_format(stream, "finit"); break;
 
 					case 0x28: case 0x29: case 0x2a: case 0x2b: case 0x2c: case 0x2d: case 0x2e: case 0x2f:
-						sprintf(s, "fucomi  st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fucomi  st(0),st(%d)", op2 & 0x7); break;
 
 					case 0x30: case 0x31: case 0x32: case 0x33: case 0x34: case 0x35: case 0x36: case 0x37:
-						sprintf(s, "fcomi   st(0),st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fcomi   st(0),st(%d)", op2 & 0x7); break;
 
-					default: sprintf(s, "??? (FPU)"); break;
+					default: util::stream_format(stream, "??? (FPU)"); break;
 				}
 			}
 			break;
@@ -1337,14 +1336,14 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fadd    qword ptr %s", modrm_string); break;
-					case 1: sprintf(s, "fmul    qword ptr %s", modrm_string); break;
-					case 2: sprintf(s, "fcom    qword ptr %s", modrm_string); break;
-					case 3: sprintf(s, "fcomp   qword ptr %s", modrm_string); break;
-					case 4: sprintf(s, "fsub    qword ptr %s", modrm_string); break;
-					case 5: sprintf(s, "fsubr   qword ptr %s", modrm_string); break;
-					case 6: sprintf(s, "fdiv    qword ptr %s", modrm_string); break;
-					case 7: sprintf(s, "fdivr   qword ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fadd    qword ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "fmul    qword ptr %s", modrm_string); break;
+					case 2: util::stream_format(stream, "fcom    qword ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "fcomp   qword ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "fsub    qword ptr %s", modrm_string); break;
+					case 5: util::stream_format(stream, "fsubr   qword ptr %s", modrm_string); break;
+					case 6: util::stream_format(stream, "fdiv    qword ptr %s", modrm_string); break;
+					case 7: util::stream_format(stream, "fdivr   qword ptr %s", modrm_string); break;
 				}
 			}
 			else
@@ -1352,24 +1351,24 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				switch (op2 & 0x3f)
 				{
 					case 0x00: case 0x01: case 0x02: case 0x03: case 0x04: case 0x05: case 0x06: case 0x07:
-						sprintf(s, "fadd    st(%d),st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fadd    st(%d),st(0)", op2 & 0x7); break;
 
 					case 0x08: case 0x09: case 0x0a: case 0x0b: case 0x0c: case 0x0d: case 0x0e: case 0x0f:
-						sprintf(s, "fmul    st(%d),st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fmul    st(%d),st(0)", op2 & 0x7); break;
 
 					case 0x20: case 0x21: case 0x22: case 0x23: case 0x24: case 0x25: case 0x26: case 0x27:
-						sprintf(s, "fsubr   st(%d),st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fsubr   st(%d),st(0)", op2 & 0x7); break;
 
 					case 0x28: case 0x29: case 0x2a: case 0x2b: case 0x2c: case 0x2d: case 0x2e: case 0x2f:
-						sprintf(s, "fsub    st(%d),st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fsub    st(%d),st(0)", op2 & 0x7); break;
 
 					case 0x30: case 0x31: case 0x32: case 0x33: case 0x34: case 0x35: case 0x36: case 0x37:
-						sprintf(s, "fdivr   st(%d),st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fdivr   st(%d),st(0)", op2 & 0x7); break;
 
 					case 0x38: case 0x39: case 0x3a: case 0x3b: case 0x3c: case 0x3d: case 0x3e: case 0x3f:
-						sprintf(s, "fdiv    st(%d),st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fdiv    st(%d),st(0)", op2 & 0x7); break;
 
-					default: sprintf(s, "??? (FPU)"); break;
+					default: util::stream_format(stream, "??? (FPU)"); break;
 				}
 			}
 			break;
@@ -1384,14 +1383,14 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fld     qword ptr %s", modrm_string); break;
-					case 1: sprintf(s, "??? (FPU)"); break;
-					case 2: sprintf(s, "fst     qword ptr %s", modrm_string); break;
-					case 3: sprintf(s, "fstp    qword ptr %s", modrm_string); break;
-					case 4: sprintf(s, "frstor  %s", modrm_string); break;
-					case 5: sprintf(s, "??? (FPU)"); break;
-					case 6: sprintf(s, "fsave   %s", modrm_string); break;
-					case 7: sprintf(s, "fstsw   word ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fld     qword ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "??? (FPU)"); break;
+					case 2: util::stream_format(stream, "fst     qword ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "fstp    qword ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "frstor  %s", modrm_string); break;
+					case 5: util::stream_format(stream, "??? (FPU)"); break;
+					case 6: util::stream_format(stream, "fsave   %s", modrm_string); break;
+					case 7: util::stream_format(stream, "fstsw   word ptr %s", modrm_string); break;
 				}
 			}
 			else
@@ -1399,21 +1398,21 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				switch (op2 & 0x3f)
 				{
 					case 0x00: case 0x01: case 0x02: case 0x03: case 0x04: case 0x05: case 0x06: case 0x07:
-						sprintf(s, "ffree   st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "ffree   st(%d)", op2 & 0x7); break;
 
 					case 0x10: case 0x11: case 0x12: case 0x13: case 0x14: case 0x15: case 0x16: case 0x17:
-						sprintf(s, "fst     st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fst     st(%d)", op2 & 0x7); break;
 
 					case 0x18: case 0x19: case 0x1a: case 0x1b: case 0x1c: case 0x1d: case 0x1e: case 0x1f:
-						sprintf(s, "fstp    st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fstp    st(%d)", op2 & 0x7); break;
 
 					case 0x20: case 0x21: case 0x22: case 0x23: case 0x24: case 0x25: case 0x26: case 0x27:
-						sprintf(s, "fucom   st(%d), st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fucom   st(%d), st(0)", op2 & 0x7); break;
 
 					case 0x28: case 0x29: case 0x2a: case 0x2b: case 0x2c: case 0x2d: case 0x2e: case 0x2f:
-						sprintf(s, "fucomp  st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fucomp  st(%d)", op2 & 0x7); break;
 
-					default: sprintf(s, "??? (FPU)"); break;
+					default: util::stream_format(stream, "??? (FPU)"); break;
 				}
 			}
 			break;
@@ -1428,14 +1427,14 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fiadd   word ptr %s", modrm_string); break;
-					case 1: sprintf(s, "fimul   word ptr %s", modrm_string); break;
-					case 2: sprintf(s, "ficom   word ptr %s", modrm_string); break;
-					case 3: sprintf(s, "ficomp  word ptr %s", modrm_string); break;
-					case 4: sprintf(s, "fisub   word ptr %s", modrm_string); break;
-					case 5: sprintf(s, "fisubr  word ptr %s", modrm_string); break;
-					case 6: sprintf(s, "fidiv   word ptr %s", modrm_string); break;
-					case 7: sprintf(s, "fidivr  word ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fiadd   word ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "fimul   word ptr %s", modrm_string); break;
+					case 2: util::stream_format(stream, "ficom   word ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "ficomp  word ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "fisub   word ptr %s", modrm_string); break;
+					case 5: util::stream_format(stream, "fisubr  word ptr %s", modrm_string); break;
+					case 6: util::stream_format(stream, "fidiv   word ptr %s", modrm_string); break;
+					case 7: util::stream_format(stream, "fidivr  word ptr %s", modrm_string); break;
 				}
 			}
 			else
@@ -1443,26 +1442,26 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				switch (op2 & 0x3f)
 				{
 					case 0x00: case 0x01: case 0x02: case 0x03: case 0x04: case 0x05: case 0x06: case 0x07:
-						sprintf(s, "faddp   st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "faddp   st(%d)", op2 & 0x7); break;
 
 					case 0x08: case 0x09: case 0x0a: case 0x0b: case 0x0c: case 0x0d: case 0x0e: case 0x0f:
-						sprintf(s, "fmulp   st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fmulp   st(%d)", op2 & 0x7); break;
 
-					case 0x19: sprintf(s, "fcompp"); break;
+					case 0x19: util::stream_format(stream, "fcompp"); break;
 
 					case 0x20: case 0x21: case 0x22: case 0x23: case 0x24: case 0x25: case 0x26: case 0x27:
-						sprintf(s, "fsubrp  st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fsubrp  st(%d)", op2 & 0x7); break;
 
 					case 0x28: case 0x29: case 0x2a: case 0x2b: case 0x2c: case 0x2d: case 0x2e: case 0x2f:
-						sprintf(s, "fsubp   st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fsubp   st(%d)", op2 & 0x7); break;
 
 					case 0x30: case 0x31: case 0x32: case 0x33: case 0x34: case 0x35: case 0x36: case 0x37:
-						sprintf(s, "fdivrp  st(%d), st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fdivrp  st(%d), st(0)", op2 & 0x7); break;
 
 					case 0x38: case 0x39: case 0x3a: case 0x3b: case 0x3c: case 0x3d: case 0x3e: case 0x3f:
-						sprintf(s, "fdivp   st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fdivp   st(%d)", op2 & 0x7); break;
 
-					default: sprintf(s, "??? (FPU)"); break;
+					default: util::stream_format(stream, "??? (FPU)"); break;
 				}
 			}
 			break;
@@ -1477,29 +1476,29 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 				handle_modrm( modrm_string );
 				switch ((op2 >> 3) & 0x7)
 				{
-					case 0: sprintf(s, "fild    word ptr %s", modrm_string); break;
-					case 1: sprintf(s, "??? (FPU)"); break;
-					case 2: sprintf(s, "fist    word ptr %s", modrm_string); break;
-					case 3: sprintf(s, "fistp   word ptr %s", modrm_string); break;
-					case 4: sprintf(s, "fbld    %s", modrm_string); break;
-					case 5: sprintf(s, "fild    qword ptr %s", modrm_string); break;
-					case 6: sprintf(s, "fbstp   %s", modrm_string); break;
-					case 7: sprintf(s, "fistp   qword ptr %s", modrm_string); break;
+					case 0: util::stream_format(stream, "fild    word ptr %s", modrm_string); break;
+					case 1: util::stream_format(stream, "??? (FPU)"); break;
+					case 2: util::stream_format(stream, "fist    word ptr %s", modrm_string); break;
+					case 3: util::stream_format(stream, "fistp   word ptr %s", modrm_string); break;
+					case 4: util::stream_format(stream, "fbld    %s", modrm_string); break;
+					case 5: util::stream_format(stream, "fild    qword ptr %s", modrm_string); break;
+					case 6: util::stream_format(stream, "fbstp   %s", modrm_string); break;
+					case 7: util::stream_format(stream, "fistp   qword ptr %s", modrm_string); break;
 				}
 			}
 			else
 			{
 				switch (op2 & 0x3f)
 				{
-					case 0x20: sprintf(s, "fstsw   aw"); break;
+					case 0x20: util::stream_format(stream, "fstsw   aw"); break;
 
 					case 0x28: case 0x29: case 0x2a: case 0x2b: case 0x2c: case 0x2d: case 0x2e: case 0x2f:
-						sprintf(s, "fucomip st(%d)", op2 & 0x7); break;
+						util::stream_format(stream, "fucomip st(%d)", op2 & 0x7); break;
 
 					case 0x30: case 0x31: case 0x32: case 0x33: case 0x34: case 0x35: case 0x36: case 0x37:
-						sprintf(s, "fcomip  st(%d),st(0)", op2 & 0x7); break;
+						util::stream_format(stream, "fcomip  st(%d),st(0)", op2 & 0x7); break;
 
-					default: sprintf(s, "??? (FPU)"); break;
+					default: util::stream_format(stream, "??? (FPU)"); break;
 				}
 			}
 			break;
@@ -1507,7 +1506,7 @@ static void handle_fpu(char *s, uint8_t op1, uint8_t op2)
 	}
 }
 
-static void decode_opcode(char *s, const NEC_I386_OPCODE *op, uint8_t op1 )
+static void decode_opcode(std::ostream &stream, const NEC_I386_OPCODE *op, uint8_t op1 )
 {
 	int i;
 	uint8_t op2;
@@ -1516,7 +1515,7 @@ static void decode_opcode(char *s, const NEC_I386_OPCODE *op, uint8_t op1 )
 	{
 		case TWO_BYTE:
 			op2 = FETCHD();
-			decode_opcode( s, &necv_opcode_table2[op2], op1 );
+			decode_opcode( stream, &necv_opcode_table2[op2], op1 );
 			return;
 
 		case SEG_PS:
@@ -1526,14 +1525,14 @@ static void decode_opcode(char *s, const NEC_I386_OPCODE *op, uint8_t op1 )
 			segment = op->flags;
 			op2 = FETCH();
 			if (Iconfig) op2 = Iconfig[op2];
-			decode_opcode( s, &necv_opcode_table1[op2], op1 );
+			decode_opcode( stream, &necv_opcode_table1[op2], op1 );
 			return;
 
 		case PREFIX:
-			s += sprintf( s, "%-8s", op->mnemonic );
+			util::stream_format( stream, "%-8s", op->mnemonic );
 			op2 = FETCH();
 			if (Iconfig) op2 = Iconfig[op2];
-			decode_opcode( s, &necv_opcode_table1[op2], op1 );
+			decode_opcode( stream, &necv_opcode_table1[op2], op1 );
 			return;
 
 		case GROUP:
@@ -1541,7 +1540,7 @@ static void decode_opcode(char *s, const NEC_I386_OPCODE *op, uint8_t op1 )
 			for( i=0; i < ARRAY_LENGTH(group_op_table); i++ ) {
 				if( strcmp(op->mnemonic, group_op_table[i].mnemonic) == 0 )
 				{
-					decode_opcode( s, &group_op_table[i].opcode[MODRM_REG1], op1 );
+					decode_opcode( stream, &group_op_table[i].opcode[MODRM_REG1], op1 );
 					return;
 				}
 			}
@@ -1549,7 +1548,7 @@ static void decode_opcode(char *s, const NEC_I386_OPCODE *op, uint8_t op1 )
 
 		case FPU:
 			op2 = FETCHD();
-			handle_fpu( s, op1, op2);
+			handle_fpu( stream, op1, op2);
 			return;
 
 		case MODRM:
@@ -1557,29 +1556,29 @@ static void decode_opcode(char *s, const NEC_I386_OPCODE *op, uint8_t op1 )
 			break;
 	}
 
-	s += sprintf( s, "%-8s", op->mnemonic );
+	util::stream_format( stream, "%-8s", op->mnemonic );
 	dasm_flags = op->dasm_flags;
 
 	if( op->param1 != 0 ) {
-		s = handle_param( s, op->param1 );
+		handle_param(stream, op->param1);
 	}
 
 	if( op->param2 != 0 ) {
-		s += sprintf( s, "," );
-		s = handle_param( s, op->param2 );
+		util::stream_format( stream, "," );
+		handle_param(stream, op->param2);
 	}
 
 	if( op->param3 != 0 ) {
-		s += sprintf( s, "," );
-		s = handle_param( s, op->param3 );
+		util::stream_format( stream, "," );
+		handle_param(stream, op->param3);
 	}
 	return;
 
 handle_unknown:
-	sprintf(s, "???");
+	util::stream_format(stream, "???");
 }
 
-int necv_dasm_one(char *buffer, uint32_t eip, const uint8_t *oprom, const uint8_t *decryption_table)
+int necv_dasm_one(std::ostream &stream, uint32_t eip, const uint8_t *oprom, const uint8_t *decryption_table)
 {
 	uint8_t op;
 	Iconfig = decryption_table;
@@ -1593,10 +1592,19 @@ int necv_dasm_one(char *buffer, uint32_t eip, const uint8_t *oprom, const uint8_
 
 	if (Iconfig) op = Iconfig[op];
 
-	decode_opcode( buffer, &necv_opcode_table1[op], op );
+	decode_opcode( stream, &necv_opcode_table1[op], op );
 	return (pc-eip) | dasm_flags | DASMFLAG_SUPPORTED;
 }
 
+int necv_dasm_one(char *buffer, uint32_t eip, const uint8_t *oprom, const uint8_t *decryption_table)
+{
+	std::ostringstream stream;
+	int result = necv_dasm_one(stream, eip, oprom, decryption_table);
+	std::string stream_str = stream.str();
+	strcpy(buffer, stream_str.c_str());
+	return result;
+}
+
 CPU_DISASSEMBLE( nec )
 {
 	return necv_dasm_one(buffer, pc, oprom, nullptr);
diff --git a/src/devices/cpu/nec/v25.cpp b/src/devices/cpu/nec/v25.cpp
index 6c19555718c..ebce1dbaa90 100644
--- a/src/devices/cpu/nec/v25.cpp
+++ b/src/devices/cpu/nec/v25.cpp
@@ -44,6 +44,7 @@ typedef uint32_t DWORD;
 
 #include "v25.h"
 #include "v25priv.h"
+#include "nec_common.h"
 
 const device_type V25 = &device_creator<v25_device>;
 const device_type V35 = &device_creator<v35_device>;
@@ -413,8 +414,6 @@ void v25_common_device::execute_set_input(int irqline, int state)
 
 offs_t v25_common_device::disasm_disassemble(char *buffer, offs_t pc, const uint8_t *oprom, const uint8_t *opram, uint32_t options)
 {
-	extern int necv_dasm_one(char *buffer, uint32_t eip, const uint8_t *oprom, const uint8_t *decryption_table);
-
 	return necv_dasm_one(buffer, pc, oprom, m_v25v35_decryptiontable);
 }