微机原理总结——IA-32结构微处理器发展的特点

IA-32结构微处理器发展的特点

处理器特点8086处理器16位处理器,16位寄存器和外部数据总线,20位地址总线, 1MB的地址空间386处理器32位处理器,32位寄存器，向后兼容,32位地址总线4GB的虚拟地址4KB固定尺寸页提供一种虚拟储存管理方法(分页)486处理器在386基础上引入8KB的一级缓存(Cache)首次把x86FPU集成到处理器上奔腾(Pentium)处理器增加第二执行流水线以达到超标量性能Cache加倍,8KB代码,8KB内存增加可编程控制器(APIC)支持多个奔腾处理系统P6处理器基于新的超标量微结构PentiumⅡ处理器MMX技术应用到P6PentiumⅢ处理器引进SIMD至IA-32Pentium4处理器基于Intel NetBurst微结构处理器Intel超线程处理器引入超线程(HT)技术Intel双核技术引入双核技术Intel64位处理器数据宽度64位

回顾冯诺依曼计算机体系结构的特点

1.使用单一的处理部件来完成计算、存储以及通信的工作。 2.存储单元是定长的线性组织。 3.存储空间的单元是直接寻址的。 4.使用低级机器语言，指令通过操作码来完成简单的操作。 5.对计算进行集中的顺序控制。 6.计算机硬件系统由运算器、存储器、控制器、输入设备、输出设备五大部件组成并规定了它们的基本功能

FLAGS

状态标志位 CF 0 进位AF 4 辅助进位(用的少)OF 11 溢出SF 7 符号PF 2 奇偶 ParityZF 6 零 2.控制标志位DF 方向 DF=1 自动减 即从右到左IF 中断允许TF 追踪

The types of flags within the simple 8086 CPU are as follows, with their abbreviation(缩写) in parentheses(括号):

Overflow (OF) Direction (DF) Interrupt Enable (IF) Sign (SF) Zero (ZF) Auxillary Carry (AF) Parity (PF) Carry (CF) （没有TF） The functions of the flags are as follows (“cleared” means a value of 0 while “set” means a value of 1):

OF - set if the result of a signed arithmetic or logic operation is too large of a positive number or too small of a negative number to fit into the CPU’s registers…

DF - set if the programmer wants to decrement the index registers (SI and DI) during string manipulation instructions. Cleared to 0 to increment.

IF - set to allow external devices to interrupt the CPU for service requests

SF - set if the most significant bit of an arithmetic/logic operation is set. Usually interpreted as a negative number when set.

ZF - set if the result of an arithmetic/logic operation is equal to 0.

AF - set if there was a carry from or borrow to bits 0-3 in the AL register.

PF - set if the number of 1s (or parity) in the low-order byte is even.

CF - set if there was a carry from or borrow to the most significant bit during last result calculation.

Now we know what the flags do, but why do their abbreviations(缩写) not match the ones in your question? Because the ones in your question refer to STATES(状态) of these flags, not the flags themselves per se.

NV - means “no overflow”, or the OF = 0

UP - means that string manipulation instructions will cause the index registers to increment, or DF = 0

EI - means interrupts are enabled, or IF = 1

PL - means a number is positive, or the SF = 0

NZ - means a number is not equal to 0, or the ZF = 0

NA - means no bits were carried or borrowed from bits 0-3 of the AL regiater, or the AF = 0

PO - means the number of ones is odd, or PF = 0

NC - means no bits were carried or borrowed from the most significant bit, or CF = 0

In conclusion, the 80x86 family has many more flags that do things such as processor control, program access control, power management, etc. Without these simple flags, computers would be utterly useless, not knowing how to compare and test binary data.

参考： http://answers.yahoo.com/question/index?qid=20061110202234AATMzc7