diff --git a/src/devices/cpu/minx/minxd.cpp b/src/devices/cpu/minx/minxd.cpp
index 73001e9ec90..8005d1ecc9f 100644
--- a/src/devices/cpu/minx/minxd.cpp
+++ b/src/devices/cpu/minx/minxd.cpp
@@ -349,85 +349,84 @@ static const minxdasm mnemonic_cf[256] = {
 };
 
 #define HANDLE_ARGUMENT                         \
-case R_A:   dst += sprintf( dst, "%cA", fill ); break;          \
-case R_B:   dst += sprintf( dst, "%cB", fill ); break;          \
-case R_L:   dst += sprintf( dst, "%cL", fill ); break;          \
-case R_H:   dst += sprintf( dst, "%cH", fill ); break;          \
-case R_N:   dst += sprintf( dst, "%cN", fill ); break;          \
-case R_F:   dst += sprintf( dst, "%cF", fill ); break;          \
-case R_SP:  dst += sprintf( dst, "%cSP", fill ); break;         \
-case R_BA:  dst += sprintf( dst, "%cBA", fill ); break;         \
-case R_HL:  dst += sprintf( dst, "%cHL", fill ); break;         \
-case R_X:   dst += sprintf( dst, "%cX", fill ); break;          \
-case R_Y:   dst += sprintf( dst, "%cY", fill ); break;          \
-case R_U:   dst += sprintf( dst, "%cU", fill ); break;          \
-case R_V:   dst += sprintf( dst, "%cV", fill ); break;          \
-case R_I:   dst += sprintf( dst, "%cI", fill ); break;          \
-case R_XI:  dst += sprintf( dst, "%cXI", fill ); break;         \
-case R_YI:  dst += sprintf( dst, "%cYI", fill ); break;         \
-case R_PC:  dst += sprintf( dst, "%cPC", fill ); break;         \
+case R_A:   util::stream_format(stream, "%cA", fill); break;          \
+case R_B:   util::stream_format(stream, "%cB", fill); break;          \
+case R_L:   util::stream_format(stream, "%cL", fill); break;          \
+case R_H:   util::stream_format(stream, "%cH", fill); break;          \
+case R_N:   util::stream_format(stream, "%cN", fill); break;          \
+case R_F:   util::stream_format(stream, "%cF", fill); break;          \
+case R_SP:  util::stream_format(stream, "%cSP", fill); break;         \
+case R_BA:  util::stream_format(stream, "%cBA", fill); break;         \
+case R_HL:  util::stream_format(stream, "%cHL", fill); break;         \
+case R_X:   util::stream_format(stream, "%cX", fill); break;          \
+case R_Y:   util::stream_format(stream, "%cY", fill); break;          \
+case R_U:   util::stream_format(stream, "%cU", fill); break;          \
+case R_V:   util::stream_format(stream, "%cV", fill); break;          \
+case R_I:   util::stream_format(stream, "%cI", fill); break;          \
+case R_XI:  util::stream_format(stream, "%cXI", fill); break;         \
+case R_YI:  util::stream_format(stream, "%cYI", fill); break;         \
+case R_PC:  util::stream_format(stream, "%cPC", fill); break;         \
 case I_8:            /* 8 bit immediate */              \
 	ea = oprom[pos++];                      \
-	dst += sprintf( dst, "%c$%02X", fill, ea );         \
+	util::stream_format(stream, "%c$%02X", fill, ea);         \
 	break;                              \
 case I_16:           /* 16 bit immediate */             \
 	ea = oprom[pos++];                      \
 	ea += oprom[pos++] << 8;                    \
-	dst += sprintf( dst, "%c$%04X", fill, ea );         \
+	util::stream_format(stream, "%c$%04X", fill, ea);         \
 	break;                              \
 case D_8:            /* PC + 8 bit displacement (signed) */     \
 	ofs8 = oprom[pos++];                        \
-	dst += sprintf( dst, "%c$%04X", fill, pc + pos - 1 + ofs8 );    \
+	util::stream_format(stream, "%c$%04X", fill, pc + pos - 1 + ofs8);    \
 	break;                              \
 case D_16:           /* PC + 16 bit displacement */         \
 	ea = oprom[pos++];                      \
 	ea += oprom[pos++] << 8;                    \
 	ea = ea - 1;                            \
-	dst += sprintf( dst, "%c$%04X", fill, pc + pos + ea );      \
+	util::stream_format(stream, "%c$%04X", fill, pc + pos + ea);      \
 	break;                              \
 case S_8:            /* SP + 8 bit displacement (signed) */     \
 	ea = oprom[pos++];                      \
-	dst += sprintf( dst, "%cSP+$%02X", fill, ea );          \
+	util::stream_format(stream, "%cSP+$%02X", fill, ea);          \
 	break;                              \
-case M_IHL: dst += sprintf( dst, "%c[I+HL]", fill ); break;     \
+case M_IHL: util::stream_format(stream, "%c[I+HL]", fill); break;     \
 case M_N8:           /* [I+N+ofs8] */                   \
 	ea = oprom[pos++];                      \
-	dst += sprintf( dst, "%c[I+N+$%02X]", fill, ea );       \
+	util::stream_format(stream, "%c[I+N+$%02X]", fill, ea);       \
 	break;                              \
 case M_I16:          /* [I+ofs16] */                    \
 	ea = oprom[pos++];                      \
 	ea += oprom[pos++] << 8;                    \
-	dst += sprintf( dst, "%c[I+$%04X]", fill, ea );         \
+	util::stream_format(stream, "%c[I+$%04X]", fill, ea);         \
 	break;                              \
-case M_X:   dst += sprintf( dst, "%c[X]", fill ); break;        \
-case M_Y:   dst += sprintf( dst, "%c[Y]", fill ); break;        \
+case M_X:   util::stream_format(stream, "%c[X]", fill); break;        \
+case M_Y:   util::stream_format(stream, "%c[Y]", fill); break;        \
 case M_X8:           /* [X + 8 bit displacement (signed)] */        \
 	ea = oprom[pos++];                      \
-	dst += sprintf( dst, "%c[X+$%02X]", fill, ea );         \
+	util::stream_format(stream, "%c[X+$%02X]", fill, ea);         \
 	break;                              \
 case M_Y8:           /* [Y + 8 bit displacement (signed)] */        \
 	ea = oprom[pos++];                      \
-	dst += sprintf( dst, "%c[Y+$%02X]", fill, ea );         \
+	util::stream_format(stream, "%c[Y+$%02X]", fill, ea);         \
 	break;                              \
-case M_XL:  dst += sprintf( dst, "%c[X+L]", fill ); break;      \
-case M_YL:  dst += sprintf( dst, "%c[Y+L]", fill ); break;      \
+case M_XL:  util::stream_format(stream, "%c[X+L]", fill); break;      \
+case M_YL:  util::stream_format(stream, "%c[Y+L]", fill); break;      \
 case M_16:           /* [16bit] */                  \
 	ea = oprom[pos++];                      \
 	ea += oprom[pos++] << 8;                    \
-	dst += sprintf( dst, "%c[$%04X]", fill, ea );           \
+	util::stream_format(stream, "%c[$%04X]", fill, ea);           \
 	break;                              \
-case M_HL:  dst += sprintf( dst, "%c[HL]", fill ); break;       \
-case OP:    dst += sprintf( dst, "%c$%02X", fill, op ); break;      \
-case OP1:   dst += sprintf( dst, "%c$%02X", fill, op1 ); break;
+case M_HL:  util::stream_format(stream, "%c[HL]", fill); break;       \
+case OP:    util::stream_format(stream, "%c$%02X", fill, op); break;      \
+case OP1:   util::stream_format(stream, "%c$%02X", fill, op1); break;
 
-CPU_DISASSEMBLE( minx )
+static offs_t internal_disasm_minx(cpu_device *device, std::ostream &stream, offs_t pc, const uint8_t *oprom, const uint8_t *opram, int options)
 {
 	const minxdasm *instr;
 	uint8_t op, op1;
 	int8_t  ofs8;
 	uint16_t ea;
 	int pos = 0;
-	char *dst = buffer;
 
 	op1 = op = oprom[pos++];
 
@@ -445,7 +444,7 @@ CPU_DISASSEMBLE( minx )
 		break;
 	}
 
-	dst += sprintf( dst, "%-6s", s_mnemonic[ instr->mnemonic ] );
+	util::stream_format(stream, "%-6s", s_mnemonic[ instr->mnemonic ]);
 
 	if ( instr->argument1 ) {
 		char fill = ' ';
@@ -463,3 +462,13 @@ CPU_DISASSEMBLE( minx )
 	}
 	return pos | s_flags[instr->mnemonic] | DASMFLAG_SUPPORTED;
 }
+
+
+CPU_DISASSEMBLE(minx)
+{
+	std::ostringstream stream;
+	offs_t result = internal_disasm_minx(device, stream, pc, oprom, opram, options);
+	std::string stream_str = stream.str();
+	strcpy(buffer, stream_str.c_str());
+	return result;
+}