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Technique to Make an Intel 80188 Base Machine Substantially Compatible With an IBM Personal Computer

IP.com Disclosure Number: IPCOM000040694D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Related People

Booth, JR: AUTHOR [+5]

Abstract

An Intel 80188 microprocessor, which includes Interrupt Controller, Timers, DMA (Direct Memory Access) Controller, Chip Select Generator, Clock Generator and Bus Controller on its chip, may utilize many IBM Personal Computer (PC) application programs through the use of Application Specific Integrated Circuits (ASICs), software emulating the hardware of the IBM PC, and carefully defining compatibility with the IBM PC. This is accomplished notwithstanding the complications of temperamental timers, interrupt incompatibilities, vector violations, and DMA differences. An Intel 80188 microprocessor may be utilized as a very inexpensive word processor/typewriter in addition to having the ability to load and execute a wide variety of IBM PC programs.

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Technique to Make an Intel 80188 Base Machine Substantially Compatible With an IBM Personal Computer

An Intel 80188 microprocessor, which includes Interrupt

Controller, Timers, DMA (Direct Memory Access) Controller, Chip Select Generator, Clock Generator and Bus Controller on its chip, may utilize many IBM Personal Computer (PC) application programs through the use of Application Specific Integrated Circuits (ASICs), software emulating the hardware of the IBM PC, and carefully defining compatibility with the IBM PC. This is accomplished notwithstanding the complications of temperamental timers, interrupt incompatibilities, vector violations, and DMA differences. An Intel 80188 microprocessor may be utilized as a very inexpensive word processor/typewriter in addition to having the ability to load and execute a wide variety of IBM PC programs. When used as a very inexpensive word processor/typewriter, it can use an integrated word processing package, such as DisplayWrite 1, an integrated DOS with user menus, an integrated typewriter mode, an integrated letter- quality printer having its mechanism controlled by the Intel 80188, a typewriter-quality keyboard, a single 3.5" diskette data storage, and a liquid crystal display screen. This relatively inexpensive word processor/typewriter is shown in the block diagram. This shows that software applications of the IBM PC may have to be supplied through DOS or BIOS (Basic Input Output Systems), or directly to a direct device/hardware control. However, the software applications which have to bypass DOS and/or BIOS and be sent directly to the direct device/hardware control are non-well-behaved applications. The Intel 80188 microprocessor has three 16-bit timer/counters, but these are not compatible with an Intel 8253 multi-mode timer, which is used in the IBM PC. Because of this lack of compatibility of the timers, which are used in the Sound Generation and Time-Of-Day portions of the block diagram, it is necessary to include an Intel 8253 timer. However, it is not necessary to use any other DMA Controller except that of the Intel 80188. The IBM PC uses an Intel 8257 Interrupt Controller. Because this is substantially different from the Interrupt Controller of the Intel 80188, software must be employed to emulate the Intel 8257 Interrupt Controller. Interrupt vector collisions caused by hard-coded mapping of the internal devices of the Intel 80188 microprocessor must be IBM PC- defined vectors. Many interrupt vector collisions can be overcome by software redirection. These various interrupt vector collisions and how they can be solved are as follows: IRQ 05 PC usage ----- Print Screen

80188 usage -- Array Bounds Exception

Solution -- Do not use BOUNDS instruction (80188 only). IRQ 06

PC usage ----- Reserved

80188 usage -- Unused Opcode Exception

Solut...