The main differences between the ARM7 processor and the 8086processor were that the ARM7 was RISC based architecture and the 8086 was CISCbased architecture. To start offthe x86 family of processors Intel came out with the 8086 in 1978. Later onIntel upgraded the 8086 by making an 8088 with an 8 bit bus. In 1981 IBM startsusing the 8088 in their PC, which was a big step for Intel in making a reputablename for themselves. In 1982 Intel produced an 80286 processor that contained134,000 transistors (Anthes, Gary).
We will see this number go up continuously throughoutthe years. In 1989 the 80486 is introduced with a little over a milliontransistors. Later on the Pentium processor is produced by Intel and becomes ahit, and AMD comes out with some of their own processors.
Finally in 2006 theCore processor is introduced by Intel. Todaywe have many core i7 processors running most of the computers if not the i5which is slightly older. These are highly sought after when building a PC. Earlier itwas mentioned that a key difference between the ARM7 processor and the Intel8086 was their architecture. These two different designs go by RISC and CISC.
RISCand CISC are two different architectures with CISC being known as thepredecessor of RISC architecture. RISC stands for reduced instruction setcomputing while CISC stands for complex instruction set computing. The goal of CISCarchitecture is to reduce the amount of instructions for a program. Theseinstructions for CISC architecture tend to be quite complex. RISC is mostlyused in portable electronic devices because of its power efficiency. This typeof processor is different from a CISC processor because it uses an optimizedset of simple instructions (“RISC Vs. CISC”).
The number ofinstructions for a RISC processor tends to be high. This reduces the cycles perinstruction compared to a CISC processor and because of this RISC processorsalso tend to have a performance advantage over CISC processors. Another fewdifferences are that CISC has high cycles per second, while RISC has low. CISCalso converts instructions into microcode and then executes themicroinstruction (Agarwal, Tarun).
As one can see, the CISC and RISC processorsare different in their design. The ARM7 wasthe first RISC microprocessor available for commercial use. The ARM architecture was originally developedby Acorn computers in the 1980’s.
This processoris known for its widespread use in portable electronics that do not use a lotof power consumption. The architecture is based on Von Neumann architecture oralso known as Princeton architecture. This means it has a single memory forboth data and instructions. The ARM7 is a 32 bit architecture with 37 registersall 32 bits long.
Of the 37 registers,32 are for general purpose and the other six are status registers. Theprocessor is able to produce a speed up to 130 instructions per second. The ARM architecture has five majorcomponents being the arithmetic logic unit, booth multiplier, barrel shifter,control unit, and register file (Agarwal, Tarun). The ALU has two 32 bit inputs,as well as a 4 bit bus that allows up to 16 opcodes to be executed. The boothmultiplier has 3 32 bit inputs. The barrel shifter has a 32 bit input that canbe shifted and the instruction tells the shifter where the input will beshifted. The control unit connects all the components and brings the wholeprocessor together. The Intel8086 was another microprocessor developed by Intel between 1976 and 1978.
Thismicroprocessor however was a 16 bit chip that had CISC architecture. Thisprocessor was the start of the x86 architecture, a family of backwardscompatible processors made by Intel from the 8086 all the way up to i7 modernday processors which are very successful in the market. The 8086 processor is divided into two parts,the BIU and the EU (“Microprocessor 8086 Functional Units”). The BIU,known as the bus interface unit, handles the data on the buses for the EU orthe execution unit. The BIU has an instruction queue, instruction pointer, andsegment registers. The instruction queue is responsible for pre fetchinginstruction bytes from memory, which increases the speed of the processor. Thereare 16 segment registers in the BIU which hold addresses of instructions anddata in memory. The instruction pointer is another 16 bit register that holdsthe address of the next instruction.
The EU is responsible for decoding andexecuting these instructions. The EU has a flag register, general purposeregisters, and an arithmetic logic unit. The flag register changes its standingdepending on the flag stored in the accumulator. The general purpose registerscan store 8 bit data by dividing 16 bit data into two parts.
The arithmeticlogic unit is straightforward and handles all of the arithmetic and logicoperations. Below is a diagram of the internal architecture of an 8086processor.