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README.TXT File Release Notes for the Microsoft(R) MASM Professional Development System, Version 6.12 (C) Copyright 1997, Microsoft Corporation. All rights reserved. This document contains release notes for the Microsoft MASM Professional Development System, version 6.12. The information in this document and in the Microsoft Advisor (Online Help) is more up-to-date than the manuals. The printed documentation for MASM 6.11 has not changed from MASM 6.10. MASM 6.12 is being released as a patch for users of MASM 6.11. The MASM 6.11 installation disks provide several important files that include new or updated information for this release. They are: README.TXT =====> Contains patch installation instructions, documentation errors, system requirements, information and tips on using MASM 6.1x, and known assembler bugs. CV.TXT =========> Contains release notes for Microsoft CodeView(TM). ERRMSG.TXT =====> Contains updated information on 32-bit Linker errors, ML error messages, and Microsoft DOSXNT MS-DOS Extender error messages. SAMPLES.TXT ====> Contains information about MASM samples for MS-DOS and Microsoft Windows 3.1. NTSAMPLE.TXT ===> Contains information about MASM samples for Microsoft Windows NT. SUPPORT.TXT ====> Contains updated Microsoft Product Support policies. Information on new Intel processor instructions can be found in the following locations: Intel(R) Pentium(TM) ====> In PENTIUM.TXT installed with MASM 6.11 Intel(R) MMX(TM) ========> On the World Wide Web at: www.intel.com/drg/mmx/manuals/prm/prm.htm ======================< README.TXT Table of Contents >===================== Part 1: Patch Installation -------------------------- Part 2: Documentation Errors ---------------------------- Part 3: System Requirements --------------------------- Part 4: Tips for Using MASM 6.1x -------------------------------- - ALIAS directive - Assembling Files Generated by Compiler - Building 32-Bit Applications - 32-Bit Linking - GROUP Directive and Flat-Model Programming - Structure Packing Issues for Mixed Language Programming - /WIN32 Switch for H2INC - CD-ROM Not a Valid Target - CMP Instruction Encoding - Debugging MASM Applications under Visual C++, 32-Bit Edition, or Fortran PowerStation, 32-Bit Edition - INVOKE Command - Multi-File Assembly with MASM.EXE - NMAKE and NMAKER - Response Files - SAMPLES.TXT and NTSAMPLE.TXT - Using MASM 6.x Structures - Visual C++ 1.0/Fortran PowerStation 1.0 Compatibility - Working with MASM 5.1 Code - Working With Microsoft BASIC Far Strings - .FPO directive new to MASM 6.11a Part 5: Known Assembler Bugs ---------------------------- - Expression Order in High-Level Conditionals - Hexadecimal Constants - Initializing Nested Structures - Span-Dependent Expressions used in Macros - Span-Dependent Equates in Macros and EXTERNDEF ABS - Span-Dependent Text Equates - STRUCT and RECORD Initialization Part 6: What Has Been Fixed in 6.11d? ------------------------------------- Part 7: What Has Been Fixed in 6.12? ------------------------------------- Part 8: What Has Been Added in 6.12? ------------------------------------- ====================< Part 1: Patch Installation >========================= 1. Make backup copies of the files affected by the patch. These files are all in the MASM bin directory (for example, C:\MASM611\BIN). The following files will be affected: ML.EXE ML.ERR H2INC.EXE H2INC.ERR 2. Change to your MASM 6.11 root directory. For example: C: CD \MASM611 3. Copy the patch files to your MASM 6.11 root directory. The patch files are: PATCH.EXE PATCH.RTD PATCH.RTP 4. Run the patch program by typing: PATCH The patch program indicates its actions as it runs. When the patch has been successfully completed, you can delete the patch files. 5. Copy H2INC.EXE and H2INC.ERR from the patch diskette to your \masm611\bin directory. If you have problems installing this patch: - Check that you have all three patch files: PATCH.EXE, PATCH.RTP, and PATCH.RTD. - Make sure you have the correct version of the files to be updated. This patch will only patch files from MASM 6.11, 6.11a, or 6.11d. If, after checking these possibilities, you still have problems, please contact Microsoft Product Support. ====================< Part 2: Documentation Errors >======================= Environment and Tools, Page xxiii: Microsoft Support Services ------------------------------------------------------------- Microsoft Support Services information has been updated. See SUPPORT.TXT, in the directory in which you installed MASM, for the most current Microsoft support information and policies. Environment and Tools, Page 582: LIB Command Line Sample -------------------------------------------------------- The following example, as it appears on page 582, is incorrect: LIB FIRST +SECOND, , THIRD Instead, it should read: LIB THIRD +FIRST +SECOND Environment and Tools, Page 649, 651: _syscall and __syscall ------------------------------------------------------------ The H2INC documentation on pages 649 and 651 lists _syscall and __syscall as C keywords recognized by H2INC. These are not recognized, and should be removed. Environment and Tools, Page 819: Error Message A2156 ---------------------------------------------------- The value range given for the first parameter of the PAGE directive is incorrect; "...either 0 or a value in the range of 10-255" should read "...either 0 or a value in the range of 14-255." Reference, Page 12: ML Command-line Options /Cu and /Cx ------------------------------------------------------- /Cu is not the default command-line option, but is indicated as such in the MASM 6.10 Reference. Instead, /Cx should be indicated as the default. Reference, Page 98: LEA is no longer optimized ---------------------------------------------- The MASM 6.10 Reference indicates that the LEA instruction is encoded as a MOV when the source operand is a direct memory address. In response to programmer requests, MASM 6.1x no longer performs this optimization automatically. The optimization can be performed by using the OPATTR operator, as shown in the following macro: MOVLEA MACRO Dest, Symbol IF (OPATTR(Symbol)) AND 08h MOV Dest, OFFSET Symbol ELSE LEA Dest, Symbol ENDIF ENDM Programmer's Guide, Page 156: Using an Emulator Library ------------------------------------------------------- The sample code demonstrating floating-point instructions served by an emulator contains the directive .STARTUP. This directive should be removed. Programmer's Guide, Page 202: User-Defined Epilogues & Prologues ---------------------------------------------------------------- The documentation for user-defined epilogue and prologue code reads "Your macro function must return the parmbytes parameter." It should read "...the localbytes parameter." Programmer's Guide, Page 323: The C++/MASM Interface ---------------------------------------------------- The second sentence in the third paragraph reads: "The linkage specification applies only to called routines, not to external variables." It should read "The linkage specification applies to called routines and external variables." The last sentence in the same paragraph should be removed. Help for Runtime Error R6921 ---------------------------- The on-line help for runtime error R6921 reads "...Possibly the CONFIG.SYS file contained a line such as DEVICE=C:\OS\MM386.EXE..." The file name should read "C:\DOS\EMM386.EXE". =================< Part 3: MASM 6.12 System Requirements >================= The following are system requirements for Microsoft MASM 6.12: - Personal computer using a 386 or higher processor running Windows 95, or Windows NT version 3.1 or later. - 4 MB of available memory. - Hard disk with 10 MB available space. - One 3.5" high-density (1.44 MB) disk drive (3.5" low-density (720K) or 5.25" high-density (1.2 MB) disks available separately with coupon enclosed). To target Windows 3.1, you need one of the following: - Microsoft Windows Software Development Kit (SDK) 3.1. - Microsoft Visual C++ Development System, Standard or Professional Edition. To target Windows NT, you need one of the following: - Microsoft Windows NT Software Development Kit (SDK). - Microsoft Visual C++ Development System, 32-Bit Edition. ====================< Part 4: Tips for Using MASM 6.1x >=================== ALIAS directive --------------- The ALIAS directive is not included in the printed documentation for MASM 6.10. The ALIAS directive can be used for creating libraries that allow the linker (LINK) to map an old function to a new function. Syntax: ALIAS <alias> = <actual-name> where alias is the alternate or alias name, and actual-name is the actual name of the function or procedure. The angle brackets are required. Assembling Files Generated by Compilers --------------------------------------- Many compilers support assembly-language output. If you experience difficulty assembling the output of such compilers, you may need to assemble using the /Zm option. In some cases (for example, if the compiler inserts nondelimited comments or page numbers) it may be necessary to edit the assembly-language output by hand. Building 32-bit Applications ---------------------------- Following are a number of items you should keep in mind when building 32-bit applications with MASM 6.1x. Examples of how to create 32-bit applications can be found in the \SAMPLES\NTSAMPLE subdirectory of the directory in which you installed MASM. 32-bit Linking -------------- When you are creating a 32-bit application, you must link separately with a 32-bit linker. To prepare your object files for 32-bit linking, assemble using the following switches: - /c (assembles without linking) - /coff (causes object files to be created in Windows NT- compatible common object file format) After assembling, link with your 32-bit linker. Refer to the documentation included with your particular 32-bit linker for specific information and instructions. In addition, the sample Windows NT applications in \SAMPLES\NTSAMPLE demonstrate the use of /c, /coff, and a 32-bit linker. GROUP Directive and Flat-Model Programming ------------------------------------------ The GROUP directive has no effect when used in 32-bit flat-model programming. It is recommended that you not use the GROUP directive when programming in flat model. Using the GROUP directive with /coff will result in an error. Structure Packing Issues for Mixed Language Programming ------------------------------------------------------- Microsoft MASM uses /Zp1 as it's default setting for structure packing. This means that structures are not packed. Other languages may use other default settings for packing. For example, Microsoft C/C++ compilers prior to Visual C++ 32-bit edition use /Zp2; Visual C++ 32-bit edition uses /Zp8 as the default. Modules built using different structure packing may not be able to share structure data items, so care must be taken when using structures in mixed language programs. The packing size is a maximum, not a fixed, packing value. This means that a member must have a size equal to or larger than the packing limit before any packing is done. /WIN32 Switch for H2INC ----------------------- Use the /WIN32 switch with H2INC to convert C header files to NT-compatible MASM include files. When you use the /WIN32 switch, C int data types are converted to the 4-byte assembler equivalent DWORD (signed int data types are converted to SDWORD). Without the /WIN32 switch, H2INC converts int data types to 2-byte WORD (and signed int data types to SWORD). CD-ROM Not a Valid Target ------------------------- A CD-ROM drive is not a valid installation target for MASM 6.11. Setup may incorrectly list a CD-ROM drive on the target drive list. CMP Instruction Encoding ------------------------ MASM 6.1x uses a different encoding for the CMP <reg8>,<reg8> instruction than MASM 6.0 did. There is no difference in length or processor timing. Debugging MASM Applications under Visual C++, 32-bit Edition, or Fortran PowerStation, 32-bit Edition ------------------------------------------------------------- When debugging a pure MASM application under the 32-bit editions of Visual C++ or Fortran PowerStation, you must link in the library file (.LIB) provided with these high-level languages (LIBC.LIB in Visual C++, LIBF.LIB with Fortran PowerStation). If you do not use the .LIB file included in the high-level language, you will receive an "Access Violation" error message when you attempt to run a MASM application in either the 32-bit Visual C++ or 32-bit Fortran PowerStation integrated development environment. INVOKE Command -------------- The MASM 6.x INVOKE command does not support transferring control between 16-bit and 32-bit code segments. When the assembler encounters an INVOKE command in a 16-bit segment, it assumes that the procedure being invoked is also in a 16-bit segment. If the assembler encounters an INVOKE in a 32-bit segment, it assumes that the invoked procedure is also in a 32-bit segment. To avoid this problem, push the necessary parameters on the stack and make the appropriate call instead of using INVOKE. Multi-File Assembly with MASM.EXE --------------------------------- When assembling multiple files with MASM.EXE, you must terminate the command-line with a semicolon or a comma (for example, MASM *.asm;). Failure to do this may cause the program to appear to hang if you are running Microsoft Windows NT. If this does occur, you can terminate the program with Ctrl+C. NMAKE and NMAKER ---------------- MASM 6.11 includes two versions of the NMAKE project management utility. NMAKER.EXE is a real-mode version of the utility. NMAKE.EXE is a driver program that loads the MS-DOS extender DOSXNT into memory first, and then runs NMAKER.EXE. Using the NMAKE.EXE driver will result in faster build times. Some development tools from other manufacturers may be incompatible with NMAKE.EXE. If you encounter incompatibilities, use NMAKER.EXE instead. Response Files -------------- Information on response files is not included in the MASM 6.10 manuals; however, this information can be found in "ML Command Line Options" in Help. SAMPLES.TXT and NTSAMPLE.TXT ---------------------------- SAMPLES.TXT contains information about the MASM samples for MS-DOS/Windows; NTSAMPLE.TXT contains information about the samples given for MASM for Windows NT. Both files include information about additional tools you may need to build some of the samples. If you choose to install the sample code during the setup process, both SAMPLES.TXT and NTSAMPLE.TXT are included. SAMPLES.TXT can be found in the \MASM611\SAMPLES subdirectory; NTSAMPLE.TXT can be found in the \MASM611\SAMPLES\NTSAMPLE subdirectory. Using MASM 6.x Structures ------------------------- MASM 6.x supports a more powerful syntax for structure definition and usage than previous versions of MASM. This more powerful syntax is enabled by default. To use the older syntax, issue the OPTION OLDSTRUCTS directive (see Appendix A of the MASM Programmer's Guide for more information). NOTE: If you use nested structures, you must use the new MASM 6.x syntax. If you use nested structures, the OPTION OLDSTRUCTS directive will be ignored for the nested structure. Visual C++ 1.0/Fortran PowerStation 1.0 Compatibility ----------------------------------------------------- There are specific steps you must take to use MASM 6.1x with Microsoft Visual C++ 1.0 or Microsoft Fortran PowerStation 1.0. If you want to do mixed language programming with these products, it is recommended that: - You install Visual C++/Fortran PowerStation and MASM 6.1x in separate sub-directories. - You place \MSVC\BIN or \F32\BIN (your Visual C++ or Fortran PowerStation sub-directory) first on your path statement before \MASM611\BIN (your MASM 6.11 sub-directory). - You use NMAKE.EXE from MASM 6.11. You can do this using various methods, such as moving or renaming NMAKE.EXE installed in \MSVC or \F32 thus causing the system to continue searching your path and use the NMAKE.EXE in \MASM611. Optionally, for MASM 6.1x/Visual C++ mixed programming, you may use NMAKER.EXE which is installed with both products. When using the LINK utility included with Visual C++ 1.0, you may encounter one or both of the following warnings: LINK : warning L4017: /r : unrecognized option name; option ignored CVPACK : warning CK4007 : unrecognized option /x; option ignored These warnings do not affect the resulting program and should be ignored. Working with MASM 5.1 Code -------------------------- MASM 6.x offers major advances over previous versions of MASM. Some of these improvements require changes that make MASM 5.1 source code incompatible with MASM 6.x. To provide compatibility with code written for MASM 5.1, MASM 6.x allows you to access MASM 5.1 compatibility code in three ways: - By using the conversion driver MASM.EXE. MASM.EXE converts your existing command-line options to the new syntax, adds the compatibility option /Zm, and invokes ML.EXE. - By using ML.EXE with the /Zm option. You also need to convert command-line options to the new syntax. - By placing the statement OPTION M510 at the beginning of each file. You also need to convert command-line options to the new syntax. In most cases, using the /Zm option or OPTION M510 will be the best solution for assembling existing code. If you prefer to modify your code so it can be assembled without /Zm or OPTION M510, do the following: 1. Add the appropriate OPTION directives to your code. - Always add the following: OPTION OLDSTRUCTS ; Supports old-style structures OPTION OLDMACROS ; Supports old-style macros OPTION DOTNAME ; Supports naming identifiers with ; a leading dot [.] - If your code does not specify the .386 or .386P directive, add the following: OPTION EXPR16 ; Use 16-bit precision in expressions - If your code does not contain a .MODEL directive, add the following: OPTION OFFSET:SEGMENT ; Specifies that the OFFSET operator ; defaults to segment-relative rather ; than group-relative - If your code does not contain a .MODEL directive or if the .MODEL directive does not specify a language, add the following: OPTION NOSCOPED ; Makes code labels global rather than ; local to the procedure in which they ; appear OPTION PROC:PRIVATE ; Makes code labels defined with PROC ; local unless specified otherwise 2. Once your code assembles with the OPTION directives, remove each OPTION directive, one at a time, and reassemble the code after you remove each one. Usually, it is best to remove the OPTION directives in the opposite order in which you added them. In some cases, you may decide that you prefer the MASM 5.x compatibility behavior instead of the new MASM 6.x behavior. When this is true, do not remove the corresponding OPTION statement from your code. For more information on assembling MASM 5.1 code, see Appendix A of the MASM Programmer's Guide. Working With Microsoft BASIC Far Strings ---------------------------------------- The BASIC runtime function StringAssign does not correctly handle strings of zero length. Instead of calling StringAssign to convert a zero-length string, simply return a near pointer to a doubleword with the value 0. .FPO Directive -------------- FPO stands for Frame Pointer Omission. The .FPO directive is a feature added to MASM386 5.10.NT that controls the emission of debug records to the .debug$F segment or section of the object file. These records are the same records that the Microsoft Visual C++ 1.10 or Microsoft Fortran PowerStation compilers emit when they perform frame pointer elimination under /Oy and /Ox optimization control, respectively. Unlike the compiler, MASM never performs any such optimization. it simply passes on the information supplied by the programmer within this directive to the object file. The .FPO directive does not have to be used in order to debug assembly programs under the Microsoft Visual C++ 1.10 or Microsoft Fortran PowerStation debuggers whether they are stand alone Windows NT applications or mixed language C\Assembly or Fortran\Assembly Windows NT applications. This directive has been implemented to provide better backward compatibility with assembly code written for MASM386 5.10.NT, which is provided with the Windows NT DDK. The FPO directive should only be used on naked procedures or those procedures not declared with proto and called with invoke. Also you do not need to use the .FPO directive to debug naked procedures or on procedures that use proto and invoke. The following 6 parameters are used within the directive as follows. .FPO ( number of bytes in a procedures local variables divided by 4, number of bytes in a procedures parameters divided by 4, number of bytes in a procedure prologue, number of registers saved by a procedures prologue, If EBP is allocated, Frame Type ) Parameters Range ---------- ----- number of bytes in local variables / 4 >= 0 number of bytes in parameters / 4 0 - 65535 number of bytes in the procedure prologue 0 - 255 number of registers saved 0 - 7 If EBP is allocated 0 = false, 1 = true Frame Type 0 - 2 The valid values for the Frame Type parameter above are FRAME_FPO 0 FRAME_TRAP 1 FRAME_TSS 2 The C compiler only generates entries with FRAME_FPO. The other two types are used inside the Windows NT kernel to all stack traces across trap and tss frames that can appear in ring 0 code. Example Usages: 1) aproc proc .FPO ( 0, 0, 0, 0, 0, 0 ) ; all params are zero. ret aproc endp 2) .code push +000000001h call aproc add esp, 04h ret aproc proc push ebp mov ebp, esp .FPO ( 0, 1, 3, 1, 1, 0 ) ; 0 = no locals ; 1 = 4 byte param \ 4 ; 3 = bytes in procedure prologue ; 1 = one register saved in prologue ; 1 = if EBP was allocated ; 0 = frame type of FPO mov eax, dword ptr [ebp+8] ; move the passed param to EAX. leave ret 00h aproc endp See ERRMSG.TXT for a list of possible error messages that you may encounter when you use the .FPO directive. ======================< Part 5: Known Assembler Bugs >===================== Expression Order in High-Level Conditionals ------------------------------------------- Comparisons in high-level conditionals cannot begin with a literal. For instance, this comparison causes an error: .IF 1 == AX but this works properly: .IF AX == 1 Hexadecimal Constants --------------------- In some instances, ML might not generate the appropriate error message if it encounters a hexadecimal constant that does not have an appending "h". The following will help to ensure that hexadecimal constants are properly represented: - Make sure that all hexadecimal constants have an appending "h". - Begin all hexadecimal constants with the numeral 0. This ensures that the compiler will generate the appropriate error message if it encounters a hexadecimal constant that does not end in "h". Initializing Nested Structures ? ------------------------------ If one structure is nested within another, the inner structure's initializer list must either be empty or include a comma between every field. For example, the structure INFO declared on page 123 of the Programmer's Guide contains a structure of type DISKDRIVES, which in turn contains three BYTE fields. An object of type INFO could be initialized as: Info1 INFO { , , , , { }} ; Inner initializer list is blank or as: Info1 INFO { , , , , {1, 2, }} ; Commas for all three fields but not as: Info1 INFO { , , , , {1, 2 }} ; Error: missing last comma Span-Dependent Expressions used in Macros ----------------------------------------- MASM 6.1x evaluates macro expressions only on the first pass of assembly, but code and data are reevaluated on subsequent passes. Because of this, macro expressions which depend on the span between two addresses may not evaluate correctly. For instance, the following code will not evaluate correctly: Label1: JMP Label2 Label2: REPEAT Label2 - Label1 ; Evaluates incorrectly INC AX END View the listing file to determine if a questionable macro expression was evaluated as desired. Span-Dependent Equates in Macros and EXTERNDEF ABS -------------------------------------------------- The ABS operator causes an identifier to be exported as a relocatable unsized constant (see Programmer's Guide page 220). If ABS is used with EXTERNDEF within a macro, and the constant being exported depends on the difference between two addresses, the constant may not be exported correctly. In some cases, the listing file will show the correct value, but the value in the resulting .obj will be incorrect. For instance, the following code will not evaluate correctly: EXTERNDEF TableSize:ABS ; Will not be exported correctly MAKETABLE MACRO Table1 LABEL BYTE DB 0, 1, 2 TableSize EQU $-Table1 ENDM SEG1 SEGMENT MAKETABLE SEG1 ENDS To avoid this problem, either use the 'PUBLIC' directive in place of 'EXTERNDEF', or put a label before the equate, within the macro. Span-Dependent Text Equates --------------------------- The TEXTEQU operator is evaluated on the first assembly pass. If TEXTEQU is used with an expression that depends on the difference between two addresses, the resulting constant may be incorrect. For instance, the following code will not evaluate correctly: Label1: JMP Label2 Label2: WrongNum TEXTEQU %Label2-Label1 ; WrongNum will be incorrect STRUCT and RECORD Initialization -------------------------------- If a STRUCT containing a UNION is initialized incorrectly, it is possible that the compiler might not generate an appropriate error. If the UNION contains a RECORD, the STRUCT is initialized to the default value for the original UNION. EQU Redefinition ---------------- EQU can be redefined when a text macro is used, the following example illustrates this known bug. a EQU <T> a EQU <U> ; This second occurrence should generate an error "A2005: ; symbol redefinition" because once "a" is defined as a ; text macro it cannot be redefined to be a different kind ; of symbol. y EQU y ; This statement is syntactically correct, but any attempt ; to use "y" and you'll receive "error A2123: text macro ; nesting level too deep". =================< Part 6: What Has Been Fixed in 6.11d? >================= - The opcode generated for the FSETPM instruction has been corrected. - Errors when using the ALIAS directive and creating COFF object files have been fixed. - Errors when using the ORG directive to back patch the code being generated in a COFF object file have been fixed. - The extra byte in the listing file for instructions using 32-bit addressing modes has been removed. - Unresolved externals that could occur when a symbol appeared more than once in EXTERNDEF directives have been fixed. - You can now step through code in include files when building COFF object files. - Various Access Violations when generating COFF object files (/coff) have been fixed. ================< Part 7: What Has Been Fixed in 6.12? >=================== - Various Access Violations when generating CodeView debug information (/Zi) have been fixed. - Errors when specifying an entry point with the END directive and creating COFF object files have been fixed. - Various structure packing inconsistencies when compared to the Microsoft C/C++ compilers have been corrected. MASM 6.12 should now pack structures the same as the Microsoft C/C++ compiler when using the same packing options. ================< Part 8: What Has Been Added in 6.12? >=================== .586 and .586P Directives in MASM 6.11 -------------------------------------- The .586 directive enables assembly of non-privileged instructions available for the Pentium processor. The .586P directive enables privileged instructions in addition to the non-privileged instructions for the Pentium. The following example demonstrates implementation of the .586 directive. .586 .model flat, C .data ; .586 gives 110100111111y = 0D3Fh ; .586p gives 110110111111y = 0DBFh var1 dw @cpu IF @Cpu AND 0100000y %echo Pentium instructions enabled. ELSE %echo Pentium instructions Not enabled. ENDIF end .686 and .686P Directives in MASM 6.12 -------------------------------------- The .686 directive enables assembly of non-privileged instructions available for the Pentium Pro processor. The .686P directive enables privileged instructions in addition to the non-privileged instructions for the Pentium Pro. The following example demonstrates implementation of the .686 directive. .686 .model flat, C .data ; .686 gives 110101111111y = 0D7Fh ; .686p gives 110111111111y = 0DFFh var1 dw @cpu IF @Cpu AND 1000000y %echo Pentium Pro instructions enabled. ELSE %echo Pentium Pro instructions Not enabled. ENDIF end .MMX Directive in MASM 6.12 --------------------------------------------------------------------- The .MMX directive enables assembly of MMX instructions. Users can check to see that @Version is 612 or higher to tell if the version of MASM being used supports the .MMX directive and MMX instructions. The following example demonstrates the use of the .MMX directive. .586 .MMX .model flat, C .code ;; MMX opcodes can be assembled end