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Unformatted text preview: mit compiled programs to contain a relatively small number of instructions. A major disadvantage to CISC design is that complex instructions require a relatively long time to decode
and execute. An interpreter inside the CPU written in a language called microcode decodes and
executes each machine instruction. Once Intel released the 8086, it became necessary for all subsequent Intel processors to be backward-compatible with the ﬁrst one.
A completely different approach to microprocessor design is called Reduced Instruction
Set (RISC). A RISC consists of a relatively small number of short, simple instructions that execute
relatively quickly. Rather than using a microcode interpreter to decode and execute machine instructions, a RISC processor directly decodes and executes instructions using hardware. High-speed
engineering and graphics workstations have been built using RISC processors for many years.
Because of the huge popularity of IBM-PC–compatible computers, Intel was able to lower the
price of its processors and dominate the microprocessor market. At the same time, Intel recognized
many advantages to the RISC approach and found a way to use RISC-like features, such as overlapping execution in the Pentium series. The x86 instruction set continues to expand and improve.
2.2.5 Section Review
1. What are the x86 processor’s three basic modes of operation?
2. Name all eight 32-bit general-purpose registers.
3. Name all six segment registers.
4. What special purpose does the ECX register serve? For More BS-IT Books, Notes & Assignments visit: www.bsit.zxq.net 2.3 x86 Memory Management
Downloaded From: www.bsit.zxq.net 43 5. Besides the stack pointer (ESP), what other register points to variables on the stack?
6. Name at least four CPU status ﬂags.
7. Which ﬂag is set when the result of an unsigned arithmetic operation is too large to ﬁt into the
8. Which ﬂag is set when the result of a signed arithmetic operation is either too large or too
small to ﬁt into the destinati...
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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