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The ﬂoating-point unit (FPU) performs high-speed ﬂoating-point arithmetic. At one time a
separate coprocessor chip was required for this. From the Intel486 onward, the FPU has been
integrated into the main processor chip. There are eight ﬂoating-point data registers in the FPU,
named ST(0), ST(1), ST(2), ST(3), ST(4), ST(5), ST(6), and ST(7). The remaining control and
pointer registers are shown in Figure 2–7.
2.2.4 Overview of Intel Microprocessors
Let’s take a short trip down memory lane, starting when the IBM-PC was ﬁrst released, when
PC’s had 64 KByte of RAM and no hard drives. For More BS-IT Books, Notes & Assignments visit: www.bsit.zxq.net 40 Chapter 2 • x86
Downloaded From: www.bsit.zxq.net Processor Architecture Figure 2–7 Floating-Point Unit Registers.
80-bit Data Registers
48-bit Pointer Registers
ST(0) FPU Instruction Pointer ST(1)
ST(2) FPU Data Pointer ST(3)
ST(4) 16-bit Control Registers ST(5) Tag Register ST(6) Control Register ST(7) Status Register Opcode Register When discussing processor evolution, references to the data bus size are signiﬁcant because
they affect system performance. When a processor uses an 8-bit data bus to transfer a 32-bit integer to memory, for example, the integer must be broken into four parts, and four separate data
transfer operations are required to complete the operation. Given that there is a signiﬁcant delay
(called latency) involved in each data transfer operation, an 8-bit data bus transfers data at onefourth the speed of a 32-bit data bus.
Intel 8086 The Intel 8086 processor (1978) marked the beginning of the modern Intel architecture family. The primary innovations of the 8086 over earlier processors were that it had 16bit registers and a 16-bit data bus and used a segmented memory model permitting programs to
address up to 1 MByte of RAM. Greater access to memory made it possible to write complex
business applications. The IBM-PC (1980) contained an Intel 8088 processor, which was identical to the 8086, except it had an 8-bit data bus that mad...
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This note was uploaded on 11/29/2013 for the course CSE 451 taught by Professor Hussein during the Winter '13 term at Fatih Üniversitesi.
- Winter '13