According to David J. Bradley, an original member of the IBM development team, the company eliminated the Motorola chip from consideration because IBM was more familiar and comfortable with Intel processors. Tipping the scales was the fact that Microsoft had a ready and working BASIC interpreter available for the 8086 and, since it shared the same base code, the 8088.
The 8088 and 8086 microprocessors programming inte
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IBM then had to choose between the 8086 and the 8088. Ultimately, the decision came down to the simple economics of reducing chip count. IBM selected the 8088, a decision that allowed the company to build cheaper machines because it could use fewer ROM modules and less RAM, Bradley says.
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A microprocessor can be defined as an electronic component of a computer system that executes the instructions to perform tasks involved in computer processing. It is the most fundamental unit of computer that executes all the functions of a CPU. Till date, several types of microprocessors have been developed. But in this article, we will learn about the two earliest microprocessors, namely, 8086 and 8088 microprocessors. Both 8086 and 8088 microprocessors are widely used in embedded systems due to their various important and unique features.
This articles is primarily meant for explaining the major differences between 8086 and 8088 microprocessors. But before comparing 8086 and 8088 microprocessors, it is important to learn their basics so it becomes easier to understand the differences between them.
8086 microprocessors support two modes of operation, i.e. maximum mode and minimum mode. The maximum mode is suitable for system having multiple processors, whereas the minimum mode is suitable for system having a single processor.
8086 microprocessors have an instruction queue, which can store six instruction bytes from the memory resulting in faster processing. Historically, 8086 microprocessors were the first 16bit processor having 16-bit ALU, 16-bit registers, internal data bus, and 16-bit external data bus resulting in faster processing.
The most significant difference between the 8086 and 8088 microprocessors is that 8086 is a 16-bit microprocessor, while 8088 is an 8bit microprocessor. Both 8086 and 8088 are the earliest microprocessors developed by Intel, however they are still widely used in embedded systems due to their various important and unique features.
Intel introduced a revolutionary new processor called the 8086 back in Juneof 1978. The 8086 was one of the first 16-bit processor chips on the market; atthe time virtually all other processors were 8-bit designs. The 8086 had 16-bitinternal registers and could run a new class of software using 16-bitinstructions. It also had a 16-bit external data path, which meant it couldtransfer data to memory 16 bits at a time.
The address bus was 20 bits wide, meaning that the 8086 could address a full1MB (220) of memory. This was in stark contrast to most other chips of that timethat had 8-bit internal registers, an 8-bit external data bus, and a 16-bitaddress bus allowing a maximum of only 64KB of RAM (216).
The cost was high because the 8086 needed a 16-bit data bus rather than aless expensive 8-bit bus. Systems available at that time were 8-bit, and slowsales of the 8086 indicated to Intel that people weren't willing to pay forthe extra performance of the full 16-bit design. In response, Intel introduced akind of crippled version of the 8086, called the 8088. The 8088 essentiallydeleted 8 of the 16 bits on the data bus, making the 8088 an 8-bit chip as faras data input and output were concerned. However, because it retained the full16-bit internal registers and the 20-bit address bus, the 8088 ran 16-bitsoftware and was capable of addressing a full 1MB of RAM.
For these reasons, IBM selected the 8-bit 8088 chip for the original IBM PC.Years later, IBM was criticized for using the 8-bit 8088 instead of the 16-bit8086. In retrospect, it was a very wise decision. IBM even covered up thephysical design in its ads, which at the time indicated its new PC had a"high-speed 16-bit microprocessor." IBM could say that because the8088 still ran the same powerful 16-bit software the 8086 ran, just a littlemore slowly. In fact, programmers universally thought of the 8088 as a 16-bitchip because there was virtually no way a program could distinguish an 8088 froman 8086. This allowed IBM to deliver a PC capable of running a new generation of16-bit software, while retaining a much less expensive 8-bit design for thehardware. Because of this, the IBM PC was actually priced less at itsintroduction than the most popular PC of the time, the Apple II. For the triviabuffs out there, the IBM PC listed for $1,265 and included only 16KB of RAM,while a similarly configured Apple II cost $1,355.
After Intel produced the 8086 and 8088 chips, it turned its sights towardproducing a more powerful chip with an increased instruction set. Thecompany's first efforts along this line—the 80186 and 80188—wereunsuccessful. But incorporating system components into the CPU chip was animportant idea for Intel because it led to faster, better chips, such as the286.
The relationship between the 80186 and 80188 is the same as that of the 8086and 8088; one is a slightly more advanced version of the other. Compared CPU toCPU, the 80186 is almost the same as the 8088 and has a full 16-bit design. The80188 (like the 8088) is a hybrid chip that compromises the 16-bit design withan 8-bit external communications interface. The advantage of the 80186 and 80188is that they combine on a single chip 15 to 20 of the 8086–8088 seriessystem components—a fact that can greatly reduce the number of componentsin a computer design. The 80186 and 80188 chips were used for highly intelligentperipheral adapter cards of that age, such as network adapters.
The IBM 5150, the first PC, came with the 8088 (5-8MHz), which was identical to the 8086 except for its 8-bit internal bus. In 1982, Intel launched the 80186 CPU, which was also based on the 8086 but was built in 2,000 nm and hit more than 1 MIPS at a 6 MHz clock speed. The Tandy 2000 was among the first PCs that used the 80186.
The x86 is developed based on the Intel 8086 microprocessor and its 8088 variant where it started out as a 16-bit instruction set for 16-bit processors where many additions and extensions have been added to the x86 where it grew to 32-bit instruction sets over the years with almost entirely full backward compatibility. 2ff7e9595c
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