Transcript of the system!

Computer Organization and Design
Lecture 13 – Synchronous Digital Systems
Blu-ray vs HD-DVD war over? 
As you know, there are two different,
competing formats for the next generation DVD.
NEC just announced they will ship a dual-format
chip capable of playing discs in either format! I’ve
been saying for years: Can’t we all just get along?
www.cio.com/blog_view.html?CID=25615
Quic
TIFF (Uncompre
are needed t
QuickTi me™ and a
TIFF ( Uncompressed) decompressor
are needed to see thi s pi ctur e.
Qui ckTime™ and a
TIFF (U ncompr essed) decompressor
are needed to see thi s pi cture.
Review
C program: foo.c
Compiler
Assembly program: foo.s
Assembler
Object(mach lang module): foo.o
Linker
lib.o
Executable(mach lang pgm): a.out
Loader
Memory
What are “Comp. Organ. and Design”?
Application (Netscape)
Compiler
Software
Hardware
Assembler
Operating
System
(MacOS X)
Processor Memory I/O system
COD
Instruction Set
Architecture
Datapath & Control
Digital Design
Circuit Design
transistors
Coordination of many levels of abstraction
ISA is an important abstraction level:
contract between HW & SW
Below the Program
• High-level language program (in C)
swap
int v[], int k){
int temp;
temp = v[k];
v[k] = v[k+1];
v[k+1] = temp;
C compiler
}
• Assembly language program (for MIPS)
swap: sll
add
lw
lw
sw
sw
jr
$2, $5, 2
$2, $4,$2
$15, 0($2)
$16, 4($2)
$16, 0($2)
$15, 4($2)
$31
assembler
• Machine (object) code (for MIPS)
000000 00000 00101 0001000010000000
000000 00100 00010 0001000000100000 . . .
?
Synchronous Digital Systems
The hardware of a processor, such as the MIPS, is an
example of a Synchronous Digital System
Synchronous:
• Means all operations are coordinated by
a central clock.
 It keeps the “heartbeat” of the system!
Digital:
• Mean all values are represented by
discrete values
• Electrical signals are treated as 1’s and
0’s and grouped together to form words.
Logic Design
• Next 6 weeks: we’ll study how a modern
processor is built; starting with basic
elements as building blocks.
• Why study hardware design?
• Understand capabilities and limitations of
hardware in general and processors in
particular.
• What processors can do fast and what they
can’t do fast (avoid slow things if you want your
code to run fast!)
• Background for more detailed self-learning
• There is just so much you can do with
processors. At some point you may need to
design your own custom hardware.
PowerPC Die Photograph
Let’s look
closer…
Pentium Die Photograph
Processor Chip Connections
Transistors 101
• MOSFET（金属氧化物场效应管）
• Metal-Oxide-Semiconductor
G
Field-Effect Transistor
• Come in two types:
 n-type NMOSFET
 p-type PMOSFET
• For n-type (p-type opposite)
D
D
G
S
n-type
• If current is NOT flowing in Gate,
transistor turns “off” (cut-off)
and Drain-Source NOT connected
• If current IS flowing in Gate,
transistor turns “on” (triode)
and Drain-Source ARE connected
www.wikipedia.org/wiki/Mosfet
S
p-type
Side view
Transistor Circuit Rep. vs. Block diagram
• Chips is composed of nothing but
transistors and wires.
• Small groups of transistors form useful
building blocks.
a
0
0
1
1
b
0
1
0
1
c
1
1
1
0
• Block are organized in a hierarchy to build
higher-level blocks: ex: adders.
The Clock Signal
• In graphical form, for a brief instant.
• Distributed throughout the processor chip.
• Synchronizes all activities.
• Typical rate is 1GHz ⇒ 1ns (1 x 10-9 sec)
信号和波形
观察:
• 信号绝大多数时间
在高或低电平
• 信号值并不正好在
最值处
• 变化由时钟信号同
步
• 低电压 / 高电压 ⇒ 0 / 1
• Circuits have “restoration（恢复）” property
• 时钟控制何时信号获得新值（ Clock controls when signals
take on new values ）
Signals and Waveforms: Grouping
Signals and Waveforms: Circuit Delay
电路类型
• 同步数字系统(Synchronous Digital Systems)
由两种基本电路组成:
• Combinational Logic (CL) circuits组合逻辑电路
• 例：前面的加法电路.
• 输出仅为输入的函数.
• 与数学上的函数相似, y = f(x). (无法在两次调用之间存
储信息. 没有副作用)
• x改变, y会立即改变 (在短暂的延时之后)
• 特别注意 : 这不象函数调用! F是连续作用的. 不是被调
用的
• 状态单元(State Elements): 存储信息的电路.
Circuits with STATE (e.g., register)
• 例：寄存器、内存
• 在“LOAD”信号的控制下，寄存
器捕捉输入值，并立即存储
• 寄存器中存储的值出现在输出端（
延时一会儿后）
• 在下次”load”信号前，Input线上
的变化将无效（和组合逻辑不同，
在组合逻辑中输入的变化将立即反
映到输出）
• 这些用于短时存储（如寄存器文件
），实现数据在处理器之间的转移
Truth Tables for Representing CL Blocks
• 真值表给出了组合逻辑块
函数的精确定义
• 每行对应于每一种可能的
输入组合
• 对所有组合逻辑电路都是
可行的，但实践中，仅对
有限个输入有用
真值表（Truth Table）例子: 2-位加法器
Peer Instruction
A.
B.
C.
SW can peek at HW (past ISA abstraction
boundary) for optimizations
1:
2:
SW can depend on particular HW
3:
implementation of ISA
4:
Timing diagrams serve as a critical debugging 5:
6:
tool in the EE toolkit
7:
8:
ABC
FFF
FFT
FTF
FTT
TFF
TFT
TTF
TTT
And in conclusion…
• ISA is very important abstraction layer
• Contract between HW and SW
• Clocks control pulse of our circuits
• Voltages are analog, quantized to 0/1
• Circuit delays are fact of life
• Two types of circuits:
• Stateless Combinational Logic (&,|,~)
• State circuits (e.g., registers)