Subject: 15. Accessing 4 Gigs of Memory in Real Mode
Flat real mode is a popular name for a technique used to access up to 4 GB of memory, while remaining in real mode. This technique requires a 80386 or higher processor. The address space really is not flat, actually, this technique allows you treat one or more segments as large (32-bit) segments, thereby accessing memory above 1 MB. When the CPU accesses memory, the base address of the segment used is not described by the value currently in the appropriate register. The value is stored internally in a structure known as the descriptor cache. Changing the value of a segment register results in that segment's entry in the descriptor cache being recalculated according to the rules of the current mode. In real mode, the value of the segment register is shifted left four bits to find the base address of the segment, and the size of the segment is always 64k. In protected mode, the value in the segment register is used as an index into a descriptor table located in memory, and the base address and size (which may be as small as 4 KB, or as large as 4 GB) from the descriptor table are loaded into the descriptor cache. When the processor changes modes, the contents of the processor's internal descriptor cache are not changed. The reason is because changing them would result in (at the very least) the code segment being recalculated according to the new mode's rules, most likely causing your program to crash. Thus the program must load the segment registers with sensible values after the mode switch occurs. Consider an example where real mode code is located in segment 1000h. If switching modes caused an immediate recalculation of the descriptor cache, the processor would attempt to read entry 1000h of the descriptor table immediately upon switching to protected mode. Even if this were a valid descriptor (unlikely), it would have to have a base address identical to real mode segment 1000h (i.e., 10000h), and a size limit of 64 KB to prevent a probable crash. An invalid descriptor would cause an immediate processor exception. Normally, aside from preventing situations like that in the above example, there is little to be said about this feature. After all, as soon as you reload new values into the segment register, the descriptor cache entry for that segment will be reset according to the rules of the current mode. After switching from protected mode to real mode, however, when you load the segment registers with their new values, the segment's base address is recalculated according to real mode rules, but the size limit is not changed. After setting the 4 GB limit (which must be done in protected mode), it will stay in place until changed by another protected mode program, regardless of what values are loaded in the segment register in real mode. So, the steps to using this technique are as follows: 1. Set up a bare bones global descriptor table, with a null entry, and a single entry for a 4 GB segment. The base address of this segment is not important. 2. If you don't wish to define an interrupt descriptor table (IDT), you must disable interrupts before switching to protected mode. You do not need a full-fledged protected mode environment for this, so it is easiest just to disable interrupts and not worry about the IDT. 3. Switch to protected mode. 4. Load the segment registers you wish to change with the selector for the 4 GB segment. I recommend using FS and/or GS for this purpose, for reasons I'll describe below. 5. Return to real mode. 6. Re-enable interrupts. After these steps, you can then load your segment registers with any value you wish. Keep in mind that the base address will be calculated according to real mode rules. Loading a value of 0 into a segment register will result in a 4 GB segment beginning at physical address 0. You can use any of the usual 32-bit registers to generate offsets into this segment. Some points to keep in mind: 1. Some software depends on 64 KB segment wrap-around. While rare, it is possible that you will encounter software that crashes if the older segments (DS or ES) are 4 GB in size. For that reason, I recommend only using FS and/or GS for this purpose, as they are not used as widely as the others. 2. You should never change the limit of the code segment. The processor uses IP (not EIP) to generate offsets into the code segment in real mode; any code beyond the 64 KB mark would be inaccessible, regardless of the segment size. 3. You should never change the limit of the stack segment. This is similar to the above; the processor uses SP in real mode, rather than ESP. 4. Because of the necessity of switching to protected mode, this technique will not work in a virtual 8086 mode "DOS box" from Windows, OS/2, or any other protected mode environment. It only works when you start from plain, real mode DOS. Many memory managers also run DOS in V86 mode, and prevent the switch to protected mode. It is possible to use VCPI to work around this, but if you go to that length you will probably find that you have implemented a complete protected mode environment, and would not need to return to real mode anyway. 5. This technique will not work in the presence of any protected mode software that changes segment size limits. When that software returns control to your real mode program, the limits will be the values to which the protected mode code set them. If these limits are different that what your program used, problems can result. At the very least, your program will return incorrect results when accessing data stored in extended memory. At worst, your program will crash and burn. The benefits of this technique are many. Most importantly, you can access extended memory without resorting to slow BIOS calls or having to implement a complete DOS extender. If your program uses interrupts extensively (timer interrupts for animation or sound, for example), real mode is a better choice because protected mode handles interrupts slower. DOS itself uses this technique in HIMEM.SYS as a fast, practical method of providing access to extended memory. Code demonstrating this technique is available: ftp://x2ftp.oulu.fi/pub/msdos/programming/memory/realmem.zip For further reading on this topic, I suggest "DOS Internals," by Geoff Chappell. It is published by Addison-Wesley as part of the Andrew Schulman Programming Series. The ISBN number is 0-201-60835-9. Contributor: Sherm Pendley, grinch@access.mountain.net Last changed: 15 Jan 95 Return to the Table Of Contents------------------------------
Subject: 16. What Is Available at developer.intel.com REVISED
16.1 PENTIUM & PENTIUM PRO INFORMATION The gateway for information on the Pentium and Pentium Pro at Intel are: http://developer.intel.com/design/pentium http://developer.intel.com/design/pro Information linked to this page are: Application Notes, Datasheets, Manuals, Specification Updates, and much more. 16.2 INTEL DEVELOPMENT TOOLS The below page has links to software, hardware, evaluation kits and documentation on Intel OEM products. Areas covered are Intel Software Performance Products, Internet Technologies, Multimedia and Intel Products. http://developer.intel.com/design/develop.htm 16.3 INTEL TECHNOLOGIES Intel has overviews, in-depth system architecture tutorials and specifications on a variety of PC platform and communications technologies. Areas covered are MMX Technology, Intelligent I/O, WinSock 2, and much more. http://developer.intel.com/design/tech.htm 16.4 GET INTEL'S WEB SITE ON CDROM REVISED Have you been spending a long time on line downloading one of the many manual available from Intel's Developer Web Site. Now you can get the entire Technology and Product portions of that web site available on CDROM. You access the CDROMs with your browser. It now takes longer to launch the Acrobat reader than to download a meg .pdf file. With the Aug 98 version, the package includes three CD-ROMs: Products and Product Selectors; Tools and Motherboards; and Technologies. Call Intel Sales: 1-800-628-8686 / press 0 (US & Canada) 1-916-356-7599 (Outside US) webcd@cs.intel.com (e-mail address) The Reference SKU# is 273000 Developers' Insight CD-ROM. The current version is Aug 98 but is quite up to date for manuals. You can sign up for updates. 16.5 Intel 80386 Programmer's Reference Manual This is a very popular Intel Manual that is no longer available for downloading from Intel. Luigi Sgro has translated it into HTML and is available: http://www.global.village.it/~gigio/it386idx.htm Contributor: Raymond Moon, raymoon@moonware.dgsys.com Last changed: 19 Sep 98 Return to the Table Of Contents------------------------------
Subject: 17. Interrupts and Exceptions
"(with interrupts) the processor doesn't waste its time looking for work - when there is something to be done, the work comes looking for the processor." - Peter Norton INTERRUPTS AND EXCEPTIONS Interrupts and exceptions both alter the program flow. The difference between the two is that interrupts are used to handle external events (serial ports, keyboard ) and exceptions are used to handle instruction faults, (division by zero, undefined opcode). Interrupts are handled by the processor after finishing the current instruction. If it finds a signal on its interrupt pin, it will look up the address of the interrupt handler in the interrupt table and pass that routine control. After returning from the interrupt handler routine it will resume program execution at the instruction after the interrupted instruction. Exceptions on the other hand are divided into three kinds. These are Faults, Traps and Aborts. Faults are detected and serviced by the processor before the faulting instructions. Traps are serviced after the instruction causing the trap. User defined interrupts go into this category and can be said to be traps, this includes the MS-DOS INT 21h software interrupt, for example. Aborts are used only to signal severe system problems, when operation is no longer possible. See the below table for information on interrupt assignments in the Intel 386, 486 SX/DX processors, and the Pentium processor. Type specifies the type of exception. _____________________________________________________________________ Vector number Description _____________________________________________________________________ 0 Divide Error (Division by zero) 1 Debug Interrupt (Single step) 2 NMI Interrupt 3 Breakpoint 4 Interrupt on overflow 5 BOUND range exceeded 6 Invalid Opcode 7 Device not available (1) 8 Double fault 9 Not used in DX models and Pentium (2) 10 Invalid TSS 11 Segment not present 12 Stack exception 13 General protection fault 14 Page fault 15 Reserved 16 Floating point exception (3) 17 Alignment check (4) 18 - 31 Reserved on 3/486, See (5) for Pentium 32 - 255 Maskable, user defined interrupts _____________________________________________________________________ (1) Exception 7 is used to signal that a floating point processor is not present in the SX model. Exception 7 is used for programs and OSs that have floating point emulation. Also the DX chips can be set to trap floating point instructions by setting bit 2 of CR0. (2) Exception 9 is Reserved in the DX models and the Pentium, and is only used in the 3/486 SX models to signal Coprocessor segment overrun. This will cause an Abort type exception on the SX. (3) In the SX models this exception is called 'Coprocessor error'. (4) Alignment check is only defined in 486 and Pentiums. Reserved on any other Intel processor. (5) For Pentiums Exception 18 is used to signal what is called an 'Machine check exception'. The other interrupts, (32-255) are user defined. They differ in use from one OS to another. For a list of MS-DOS interrupts, see 'Obtaining HELPPC' (Subject #6) or Ralf Browns Interrupt List (Subject #11) Contributor: Patrik Ohman, patrik@astrakan.hgs.se Last changed: 10 Jan 95 Return to the Table Of Contents------------------------------
Subject: 18. ASM Books Available
The format is Author, Title, Level, and short description Ray Duncan Advanced MSDOS Programming Advanced Both a tutorial and a reference for MS-DOS capabilities and services, including reference sections on DOS function calls, IBM ROM BIOS, mouse driver and LAM. expanded memory. Excellent quality example programs throughout. By Peter Norton and John Socha Peter Norton's Assembly Language Book For the IBM PC Novice Good for an introduction to Assembly Language. Plenty of programming examples. Older versions of this book used to have a sample disk. As you read the book, you slowly add on code to what eventually is Disk Patch - the book's version of Norton's commercially available Disk Edit program. Great for complete beginners seeking novice rank. Maljugin, Izrailevich, Sopin, and Lavin The Revolutionary Guide to Assembly Language Novice This is one of the best introductory texts I've ever seen There are so many authors that the topic is broken down into specific categories: video, BIOS, keyboard, etc.. Most intro texts force you to follow a set plan of learning assembly, but in this book you can turn to a specific topic almost immediately. It's so-so as a reference book, however - a few tables of interrupts in the back. Maljugin, Izrailevich, Sopin, and Lavin Master Class Assembly Language Advanced Review: This is the sequel to The Revolutionary Guide To Assembly Language. Equally thick and massive, it covers many of the topics we see today - hardware interfaces, sound cards, data compression, even protected mode programming. Brief review of assembly at the beginning, but moves very quickly. Read this if you're intermediate seeking expert status. Definitely not recommended for beginners. If you are a beginner and you think you like the topics covered in this book, buy the one before it too. Also comes with a disk of source code examples from the book (MASM highly recommended, not TASM). Alan Wyatt Advanced Assembly Language Advanced This book's best feature is its comprehensive guide on device drivers. There are good chapters on controlling the mouse, file access, using memory, etc. Ralf Brown and Jim Kyle PC Interrupts - 2nd Edition Intermediate/Advanced The definitive book on interrupt programming for PCS and compatibles. Based on the freeware Interrupt List by Ralf Brown For an extensive book list without descriptions, point your web browser to http://www.alaska.net/~rrose/assembly.htm Sites with more books but no reviews are: http://www.fys.ruu.nl/~faber/Amain.html http://www.cet.com/~jvahn/80xbook.html (short descriptions) Contributors: Antonio Alonso, Solomon Chang, Paul Gilbert, Dave Navarro, Mike Schmit and James Vahn. Last changed: 6 Jul 97 Return to the Table Of Contents------------------------------
Subject: 19. ASM Code Available On The Internet
19.1 SIMTEL SITES The SimTel has a directory devoted to assembly language. ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl or http://www.simtel.net/simtel.net/msdos/asmutl-pre.html 19.2 80xxx Snippets Fidonet's echo for 80xxx programming has a collection of code that is maintained by Jim Vahn, jvahn@short.circuit.com. The collection is on the web. In addition to downloading the snippets there is an assembly language related book list. The URL is: http://www.cet.com/~jvahn The ability to get these files via e-mail has been discontinued. 19.3 X2FTP.OULU.FI This ftp site, x2ftp.oulu.fi, has some asm source code not available at the SIMTEL sites. The following describes some directories and the type of information that is available in them. Protected mode utilities and some source code: ftp://x2ftp.oulu.fi/pub/msdos/programming/pmode Some asm code: ftp://x2ftp.oulu.fi/pub/msdos/programming/source ftp://x2ftp.oulu.fi/pub/msdos/programming/progsrc 19.4 FTP.X86.ORG This ftp site contains much of the code and information available from Robert Collins' web site. ftp://ftp.x86.org/source 19.5 OMEN.COM Omen has assembly language source available from its web site. The address is: http://www.omen.com.au/Files/hdisk/asm.html Much of the code is archived in the .arj format. You will need the appropriate expansion program. One is available: ftp://ftp.simtel.net/pub/simtelnet/msdos/arcers/arj250a.exe 19.6 JUMBO JUMBO is the Official Web Shareware Site. It has a directory devoted to assembly language source code, libraries and utilities: http://www.jumbo.com/pages/programming/dos/asmutl/ 19.7 THEREEF I just found another site that carries this asm source code. This site has source code and information that I have not found elsewhere. http://www.iag.net/~philb/thereef/ftp_asm.htm 19.8 PC GAMES PROGRAMMER ENCYCLOPEDIA This encyclopedia is a collection of files related to game programming. Many of these files contain programming examples. Topics included are ASM tutorial, VGA and SVGA programming information, graphic algorithms, graphic file formats, soundcard and other PC hardware programming information. This encyclopedia is available online at the PC-GPE web page: http://www.qzx.com/pc-gpe/ 19.9 PROGRAMMERS DISTRIBUTION NETWORK ASSEMBLY LANGUAGE FILES These files appear to be a mirror of the assembly-related files distributed on FidoNet by PDN. There is one there that is a must if you want to write asm winNT and win95 applications. It is walk32_1.zip. Walk32 is a complete app and dll development kit with linker and includes files, libraries, tools, and lots of samples. MASM 6.x required. http://www.programmersheaven.com/files/asm/WALK32_1.ZIP 19.10 TENIE REMMEL'S ASSEMBLY SNIPPETS CODE COLLECTION The Assembly Snippets is a large collection of assembly language code and other information. Many files from the original 80XXX snippets, the ASM0-Z collection, and the Aquila site are included. All code is 99% guaranteed to compile under TASM. This new release contains the following items, among others: An object file disassembler A 4971 byte Tetris game Several Conway LIFE programs Assembly & Disassembly tables A demonstration of FakeMode Several powerful editors A complete DOS extender A Pentium optimization list A ModeX graphics library Info for writing antivirus You can download these rather large files from SimTel: ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/asnip40a.zip 1.41 Megs ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/asnip40b.zip 1.35 Megs ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/asnip40c.zip 1.32 Megs 19.11 PROGRAMMING - ASSEMBLY/BASM/TASM This site consist of 59 pages of assembly language related files. Many files I have not seen any where else. The only problem is that there are only five to eight files described per page. The URL to the first page is: http://www.aquila.com/menu2/area02/dr1-1.htm (**Not Available**) 19.12 JAN ZUMWALT'S ASM HEAVEN Jan Zumwalt has set up a collection of ASM source code, ASM programs and other low level information of interest to the ASM programmer. Find it at: http://www.interactive.net/~viren/asm_heaven/ Contributor: Raymond Moon, raymoon@moonware.dgsys.com Last changed: 25 Jan 98 Return to the Table Of Contents------------------------------
Subject: 20. How To Commit A File
The easiest solution is to open or create the file to be committed using Int 21h function 6ch, extended open/create. The BX register contains the desired Open Mode. One option that can be or'ed into this register is what Microsoft calls, OPEN_FLAGS_COMMIT, that has the value of 4000h. Using this option caused DOS to commit the file after each write. This function has been available (documented) since DOS 4.0. If you do not want to commit the file at each write but only when certain conditions are met, use Int 21h function 68h, commit file. The functions has been available (documented) since DOS 3.3. If you need to support versions of DOS before 3.3, the following technique will flush the all stored data without closing and opening the file. It is the opening of the file that is time consuming. 1. Use 21h function 45h to create a duplicate file handle to the file to be flushed. 2. Close that duplicate file handle. This technique will work all the way back to DOS 2.0. Contributor: Raymond Moon, raymoon@moonware.dgsys.com Last changed: 30 Jan 95 Return to the Table Of Contents------------------------------
Subject: 21. Using Extended Memory Manager
21.1 HOW TO USE XMS
XMS usage - short recipe:
1. Verify have at least 286 (pushf; pop AX; test AX,AX; js error).
2. Verify vector 2Fh set (DOS 3+ sets it during boot).
3. AX=4300h, int 2Fh, verify AL=80h (means XMS installed).
4. AX=4310h, int 2Fh, save ES:BX as dword XmsDriverAddr.
5. AH=8, call [XmsDriverAddr] - returns ax=largest free XMS memory block
size in kB (0 if error).
6. AH=9, DX=required size in kB, call [XmsDriverAddr] - allocates memory
(returns handle in DX - save it).
7. AH=0Bh, DS:SI->structure {
dword size (in bytes and must be even),
word source_handle,
dword source_offset,
word destination_handle,
dword destination_offset }
(if any handle is 0, the "offset" is Real Mode segment:offset)
8. AH=0Fh, BX=new size in kB, DX=handle, call [XmsDriverAddr] - changes
memory block size (without losing previous data).
9. AH=0Ah, DX=handle, call [XmsDriverAddr] - free handle and memory.
Initially, should process #1-#6, then can use #7 to put data in/get data
from XMS memory, or #8 to change XMS memory block size. On exit use #9 to
free allocated memory and handle.
Hint: handle cannot be 0, since zero is used as "no handle allocated"
value.
Errors for XMS calls (except AH=7 - Query A20) are signaled by AX=0. Error
code returned in BL, few codes can check for are:
80h - not implemented,
81h - VDISK detected (and it leaves no memory for XMS),
82h - A20 error (e.g., fail to enable address line A20),
A0h - all allocated,
A1h - all handles used,
A2h - invalid handle,
A3h/A4h - bad source handle/offset,
A5h/A6h - bad destination handle/offset,
A7h - bad length,
A8h - overlap (of source and destination areas on copy),
A9h - parity error (hardware error in memory),
Abh - block is locked,
00h - OK
For more info read INT 2Fh, AH=43h in Ralf Brown interrupt list.
21.2 WHAT IS THE 'LINEAR BLOCK ADDRESS' RETURNED BY LOCK MEM BLOCK?
When you lock mem block, XMS driver arranges memory governed by it in a way
the locked block forms one contiguous area in linear address space and
returns you starting address of the memory. Linear address is base address
of segment + offset in segment, in Real Mode it is segment*16+offset, in
Protected Mode the base address is kept in LDT or GDT; note offset can be
32-bit on 386+. If paging isn't enabled, linear address = physical
address. You don't need the linear address unless you use 32-bit offsets
in Real Mode or you use Protected Mode (see previous answer for explanation
of how you can access XMS memory).
Contributor: Jerzy Tarasiuk, JT@zfja-gate.fuw.edu.pl
Last Changed: 30 Jan 95
Return to the Table Of Contents
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Subject: 22. EXE2BIN Replacement
A utility, EXE2BIN, used to be included in DOS. This utility was needed to convert the output of the linker from .EXE to .COM format because the linkers could not do this directly. As linkers became more capable, the need for this utility vanished, so EXE2BIN was dropped from DOS. If you still are using an older assembler and linker, you now have been left out in the cold. Well, not quite, as there are three shareware equivalent programs. 22.1 EXECOM14.ZIP EXECOM was written by Chris Dunford in C. The .zip file contains the executable, documentation and the .c source that Chris Dunford has released into the public domain. The current version is 1.04 with a 2 Mar 88 date. ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/execom14.zip 22.2 BIN.ZIP This replacement version was written by Bob Tevithick. It is based upon versions 1.00 of Chris Dunford's program. The .zip file contains only the executable and documentation. No source is included. ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/bin.zip 22.3 X2B11.ZIP X2B is written in 100% assembly language by Henry Nettles. Again it is based upon Chris Dunford's program. The zip file contains the executable and .asm source. The documentation is in the source code. ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/x2b11.zip 22.4 THE REAL THING, EXE2BIN.EXE If you need the real thing, EXE2BIN.EXE is available on the DOS Supplemental Diskettes. This disks can be downloaded from Microsoft. for MS DOS 6.0 ftp://ftp.microsoft.com/peropsys/msdos/public/supplmnt/DOS6SUPP.EXE for MS DOS 6.2 ftp://ftp.microsoft.com/peropsys/msdos/public/supplmnt/DOS62SP.EXE for MS DOS 6.21 ftp://ftp.microsoft.com/peropsys/msdos/public/supplmnt/SUP621.EXE for MS DOS 6.22 ftp://ftp.microsoft.com/peropsys/msdos/public/supplmnt/SUP622.EXE Contributor: Raymond Moon, raymoon@moonware.dgsys.com Last changed: 8 Jan 96 Return to the Table Of Contents------------------------------
Subject: 23. ASM Tutorials Available on the Internet
There are several assembly language tutorials available on the Internet. 23.1 FROM SIMTEL MIRRORS From the SimTel Mirrors, e.g., oak.oakland.edu, there are two tutorials available in the simtel/msdos/asmutil directory. ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/asmtutor.zip The tutorial is by Joshua Averbach. It is old, as it is dated Jun 1988. It is designed for the 8088 processor. ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/primer2.zip This tutorial is designed specifically for the cheap assembler (CHASM) also available in this directory. 23.2 GAVIN ESTEY'S TUTORIAL A new tutorial has been written by Gavin Estey. He has provided his tutorial in ascii text and in htm format. They are available: htm: http://www.strangecreations.com/strange/library/assembly/tutor/asm1.htm Text: http://www.strangecreations.com/strange/library/assembly/asmtut.txt 23.3 VLA's ASSEMBLY LANGUAGE TUTORIAL This tutorial is available directly or as part of the PC Games Encyclopedia: ftp://teeri.oulu.fi/pub/msdos/programming/gpe/pcgpe10.zip or on-line at: http://www.qzx.com/pc-gpe/asm.tutorials.htm 23.4 ASM Tutorial on University of Guadalajara Web Site The on-line tutorial is available: http://udgftp.cencar.udg.mx/ingles/tutor/Assembler.htm ASCII version: http://udgftp.cencar.udg.mx/ingles/tutor/edition97/edit96.zip MS Word Version: http://udgftp.cencar.udg.mx/ingles/tutor/edition97/ENSAMDOC.ZIP 23.5 RANDALL HYDE'S ART OF ASSEMBLY LANGUAGE Randy Hyde's Assembly Language Course Material. This in my opinion is the best assembly language tutorial available on the Internet. http://cuda.ucr.edu/Page_asm/ArtOfAsm.htm Do not miss his Assembly Language Style Guide. http://cuda.ucr.edu/Page_asm/moreasm/asmstyle.pdf .pdf version http://cuda.ucr.edu/Page_asm/moreasm/asmstyle.htm htm version 23.6 PATRICK STUDDARD'S ASSEMBLY CLASS NOTES Patrick Studdard has a very extensive library of supplementary class notes for assembly language. These are available for all and not just those who are taking the class. They are available: http://www.csis.american.edu/~studdard/classes/fall1995/4028201/notes/index.htm 23.7 TORE NILSSON'S ASSEMBLY TUTORIAL PAGE VLA's Assembly and DMA programming tutorials, Asphyxia's VGA tutorials, and some graphics and sound programming information. http://www.ice-digga.com/programming/ 23.8 HOMER TILTON'S ASSEMBLY LANGUAGE TUTORIAL ZDNet offers an Assembly Language tutorial by Homer Tilton. To find it, use the following URL: http://www6.zdnet.com/cgi-bin/texis/swlib/hotfiles/info.htm?fcode=000804 23.9 Mike Babcock's ASM Tutorial Mike Babcock has a small tutorial. Unfortunately, all the links on the page currently are broken. The basic URL is: http://w3.tyenet.com/mbabcock/prg.asmtut1.htm (Note that the internal links currently are broken. I have contacted the author, and he has replied that he will be correcting this shortly.) 23.10 ASM TUTORIAL ON UNIVERSITY OF GUADALAJARA WEB SITE This tutorial is growing and is very good. Take a look. http://udgftp.cencar.udg.mx/ingles/tutor/Assembler.htm 23.11 BRIAN BROWN'S CENTRAL INSTITUTE OF TECHNOLOGY COURSE WARE Brian Brown as a very good tutorial along with others. The assembly language tutorial, version 3.0, starts: http://www.cit.ac.nz/smac/asm/astart.htm 23.12 FERDI SMIT ASSEMBLY LANGUAGE TUTORIAL Ferdi Smit has a nice tutorial in text and htm. It is available: http://www.xs4all.nl/~smit/docs.htm#asm 23.13 PROF. LOCKWOOD'S EE291 CLASS LECTURE NOTES Prof. Lockwood's class lecture notes, resources, etc. are a very good source of information on assembly language programming. His URL is: http://www.ece.uiuc.edu/~ece291/ Contributor: Raymond Moon, raymoon@moonware.dgsys.com Last changed: 9 Dec 97 Return to the Table Of Contents------------------------------
Subject: 24. Shareware Assemblers REVISED
24.1 AVAILABILITY All assemblers, unless otherwise noted, listed here are available from SimTel in the SimTel/msdos/asmutil directory. Specifically: ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl 24.2 A86 This assembler is a very capable assembler for 80286 and earlier processors. Registration will get you a version capable of handling 80386 processor. For more details, see the A86 section of this FAQ. 24.3 CHASM, CHASM4.ZIP This assembler was the first shareware assembler available. CHASM was written Mr. David Whitman. The current version available is version 4 and dated in 1983. This version supports only 8088 processor, and the output only is: .COM file (.EXE is not supported) BLOADable - format for interpreted BASIC to load and execute External procedure for TurboPascal - TurboPascal version not given The version available on the internet is annoyware and crippleware. For $40 registration fee, you will get the complete version without the annoying banner page. This version supports macros, conditional assembly, include files, operand expressions and structures. I do not recommend this assembler because of it limited capability and it is very out of date. Its URL is: ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/chasm4.zip 24.4 THE ARROWSOFT ASSEMBLER, VALARROW.ZIP This assembler is the public domain version of the Professional Arrowsoft Assembler by Arrowsoft Systems, Inc. The version is 1.00d and is dated in 1986. This assembler is a MASM 3.0 compatible assembler and supports up to 80286 processor. Compared to the Professional version, the public domain version has one major limitation. The file input size is limited to 64K bytes. The file also includes a public domain linker, full screen editor and an EXE2BIN clone program. The above version 1.00d is available from SimTel. Version 2.00c which has only the assembler and documentation is available: http://sunsite.unc.edu/pub/micro/pc-stuff/freedos/files/arrowasm.zip and the linker separately: http://sunsite.unc.edu/pub/micro/pc-stuff/freedos/files/vallink.zip These are used in the freeDOS project. Rick Elbers maintains several web pages dedicated to this assembler. If you use this assembler, visit this site. http://www.geocities.com/SiliconValley/Heights/7052/valarr.htm 24.5 WOLFWARE ASSEMBLER, WASM223.ZIP This assembler was written by Mr. Eric Tauck. The latest version is 2.23 and dates from 1991. This assembler supports up to the 80286 processor. It will assemble directly into a .COM file or .obj file. It supports a simplified syntax and program structure so programs written for this assembler may not be compatible with other assemblers. Several source files for programs are included with the .zip file. It is available from the author at: ftp://ftp.mc.net/pub/users/warp/wasm223.zip 24.6 MAGIC ASSEMBLER, ASM110.ZIP The version is 1.10 and dates from March 1995. This assembler was written by Mr. Bert Greevenbosch. The output is either a .COM file or a boot sector program. The assembly commands are standard except for the jump and call commands. Again, the source code will not be compatible with other assemblers. Beware of version 1.04. That version had a bug that when executed without the print command, the assembler terminated with a runtime error. This is corrected in subsequent versions. Changes made in version 1.10 are: CALLF [] added, CALL [] corrected Boot Indicator (55aa) added [BX][SI] now recognized as [BX+SI] Calculations (*, /, -, +) added XCHG added Assembling Report added EQU bug corrected IN/OUT command improved ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/asm110.zip 24.7 GEMA, GEMA.ZIP This assembler revision is 2.6a with a date, 7 Jan 96. It is different from all other x86 assemblers I have seen. This assembler is based upon Motorola's 68k mnemonics and logical structure. All instructions, Pentium Pro and known undocumented are supported. GEMA was designed especially for 32-bit processing. The assembler will take only one source code file and will output an .COM or .EXE file. No linker is required. DESA.EXE, a beta GEMA disassembler is available in the GEMA package. ASM2GEMA.EXE, a TASM to GEMA translator is no longer available as part of the GEMA package. An interactive real and protected-mode debugger is in progress. This assembler is available from: ftp://ftp.nether.net/pub/gema/gema.zip (ftp connections refused) http://prinz.hannover.sgh-net.de/~londberg/Gema.zip 24.8 NASM The birth of this assembler started out of a thread that started on comp.lang.asm.x86. When you download this assembler, you get the source code in ANSI C. The web page devoted to this assembler is: http://www.cryogen.com/Nasm/ http://www.web-sites.co.uk/nasm/ NASM is an 80x86 assembler designed for portability and modularity. It supports a range of object file formats including Linux a.out and ELF, COFF, Microsoft 16-bit OBJ and Win32. It will also output plain binary files. Its syntax is designed to be simple and easy to understand, similar to Intel's but less complex. It supports Pentium, P6 and MMX opcodes, and has macro capability. It includes a disassembler as well. Major new features present in this release include: 1. The long-awaited listing file support! 2. Support for a search path for include files. 3. OS/2 object file support, although it's experimental as yet (could anyone with OS/2 _please_ give it a testing for me?). 4. This release, and all NASM releases from now on, include pre-built Win32 versions of NASM and NDISASM, as well as the 16-bit DOS versions. 5. Numerous bug fixes, including the repeatedly-reported bug about blank lines in macro definitions, and the one that prevented 32-bit OBJ files working with some linkers. The assembler also is available from: ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/nasm097.zip assembler ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/nasm097d.zip docs ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/nasm097s.zip source 24.9 GAS, GNU Assembler This assembler with many object-file utilities will run on 386 systems running the following operating systems: AIX 386BSD, NetBSD, BSDI/386, Linux, SCO, Unixware, DOS/DJGPP. The below file is a gzipped tar file. You will need gzip and tar programs to uncompress and extract the files. The assembler and utilities are part of the GNU binutils file. ftp://prep.ai.mit.edu/pub/gnu/binutils-2.8.tar.gz 5018 Kb ftp://prep.ai.mit.edu/pub/gnu/binutils-2.8-2.8.1-patch.gz 36 Kb 24.10 REAL TOOLS 1.0 (BETA), RTOOLS.ZIP This assembler is dated in Dec 93 and is a beta test. The nice thing about this assembler is that it comes with its own DOS-windowing IDE. This assembler was written by International Systems development. The instruction set supported is 486 including protected mode instructions, but some holes do exist. This assembler has a unique way of supporting macros. 32-bit supported. On line help and debugger are available with registered product. ftp://ftp.simtel.net/pub/simtelnet/msdos/asmutl/rtools.zip 24.11 GENERAL ASSEMBLER, GASM01G.ZIP This is a new assembler written by Jim Gage. This version outputs .COM files and can be used to write device drivers. Another version supporting up to the 486 instruction set and .obj output is in the works. This assembler is available: http://www.engr.uark.edu/~jrg/gasm/gasm01f.zip 24.12 CROSS FIRE ASSEMBLER This assembler is an 80x86 assembler that uses 680x0 syntax. If you are coming from the 680x0 environment, you may want to try this as your first assembler. This assembler supports up to the pentium instruction set, 16 and 32 bit segments, supports direct generation of .com, .exe, .sys, and more file formats, and supports pmode programming. This package comes with its own pmode DOS extender by TRAN. Currently, the math coprocessor, MMX instructions and .obj output is not supported. You can get this assembler: ftp://www.simtel.net/pub/simtelnet/msdos/asmutl/xfire510.zip 24.13 JAS Assembler (DJGPP ASM) Nicola Gaggi has written an assembler for DJGPP that is based upon NASM. Jas has a syntax much like TASM and is faster because it is a one pass assembler. Download it from: ftp://teeri.oulu.fi/pub/msdos/programming/djgpp2/jas12.zip Version 1.3 should be available soon. 24.14 Rodrigo Augusto's IASM V1.0 NEW The Intel Architecture Assembler v1.0 is a plataform independent assembler developed for the Intel 80x86 family of microprocessors. It has a simple syntax. The assembler was developed to get an easy to use flat memory assembler. A linker is not necessary as the assembler outputs a .COM file, but this can be changed. IASM supports instructions from all the Intel family, from the 8086/8088 ntil the Pentium II, MMX and floating point also is supported. IASM can generate both 16 and 32 bits code. The assembler is available from Rodrigo Augusto's home page: http://www.dcc.ufmg.br/~augusto/project/ 24.15 The Visual Assembler NEW This assembler currently is under development, but it should be worth watching. It is an attempt to apply Rapid Applicatin Development techniques to assembly language programming. The Visual Assembler is being developed based that assembly language can be used quickly and easily to program Win32 applications throgh the careful impementation and use of reuseable class modules rather than classes. The Visual Assembler is being build around an IDE that will make extensive use wizard modules that will guide the user through creating Win32 applications, libraries, drivers and VxDs. The IDE will have integrated tools including a debugger, calculator, binary editor, and disassembler. The IDE will support assembling through linking to the final program. The home page of this effort is: http://www.fortunecity.com/skyscraper/lycos/403/ Contributor: Raymond Moon, raymoon@moonware.dgsys.com Last changed: 19 Sep 98 Return to the Table Of Contents------------------------------
Subject: 25. Undocumented OpCodes
25.1 WHAT AND WHERE Robert Collins has make available an excellent article on Intel Undocumented OpCodes. Just set your web browser to: http://www.x86.org/secrets/OpCodes.htm 25.2 EXTENDED FORMS OF AAM AND AAD INSTRUCTIONS Mr. Collins describes extended forms these two instructions. AAM is ASCII Adjust after Multiplication, and ADD is ASCII Adjust before Division. These instructions are known as quick ways to divide and multiply by ten, as these instructions normally assemble with 10 as the default operand. Using macros provided, any value from 0h to 0ffh can be substituted. These instructions are available on all x86 Intel processors. 25.3 SALC - SET AL ON CARRY Mr. Collins describes this instruction a C programmers dream instruction for interfacing to assembly language procedures. This instruction will set the AL register to 00h or 0ffh depending on whether the carry flag is clear or set, respectively. This instruction is available on all x86 Intel processors. 25.4 ICE RELATED OPCODES Mr. Collins describes several instructions that appear whose existence makes debugging run-time code easier on the ICE debugger. There are: ICEBP - ICE Break Point UMOV - User Move Data LOADALL - Loads the Entire CPU State Contributor: Raymond Moon, raymoon@moonware.dgsys.com Last changed: 4 Nov 95 Return to the Table Of Contents