Mark Franklin, S06 CS, CoE, EE 362 Digital Computers II: Architecture Prof. Mark Franklin: Course Assistants: –Drew Frank: Required Book: “Heuring & Jordan” 2 nd Edition Optional Book: “Intro. VHDL” Yalamanchili Read: Academic Integrity Statement. Course Web Site:

Mark Franklin, S06 Four Key Questions What components must every computer have ? How can computers be described, specified and evaluated ? What constitutes computer architecture (hardware, software, firmware, algorithms, etc.) ? How does technology effect computer architecture (chip size, feature size, power, pin density, etc) ?

Mark Franklin, S06 Essential Computer Components Processor: interpret/execute instructions. Memory: store instructions & data. Communication Device(s): communicate with outside world, I/O. Processor Control Unit ALU Memory Input/ Output Classic Computer Architecture (SISD: Single Instruction Stream-Single Data Stream)

Mark Franklin, S06 Architecture Components INSTRUCTION SET DESIGN: Programmer visible instruction set Algorithm, compiler, OS design, algorithmic complexity HIGH LEVEL COMPONENT ORGANIZATION: Memory system, bus structure, processor design, branch handling, pipelining, execution algorithms, instructions/second, clocks/instruction. HARDWARE: Detailed logic design, packaging VLSI & Logic design CAD algorithms speed, area, power, …

Mark Franklin, S06 ALU Interconnection Network Data Memory Unit Program Control Unit Program Memory Input / Output (SIMD) Single Instruction Stream – Multiple Data Stream Architecture

Mark Franklin, S06 Performance Expression: Amdahl’s Law

Mark Franklin, S06 Amdahl’s Law It does no good to have many processors if there is not enough parallelism. What portion of a computation can be sequential if we want the processors to be used at 50 percent efficiency ? ( S = p/2 )

Mark Franklin, S06 Generalize Amdahl’s Law Speedup overall = ExTime old ExTime new = 1 (1 - Fraction enhanced ) + Fraction enhanced Speedup enhanced Example: “Suppose a program runs in 100 seconds on a machine. Multiply operations are responsible for 80 seconds of this time. How much do we have to improve the speed of multiplication if we want the program to run 4 times faster?” What about 5 times faster? PRINCIPAL: Make the common case fast!

Mark Franklin, S06 Computer Market Partitioning (costs are for processor, not system) Desktop Computing ($100 - $1,000): –Price-performance Servers: ($200 - $2,000) –Availability (reliability + effectiveness) –Scalability –Throughput Embedded Computers: ($ $1,000) –Real-time performance –Power and memory minimization –Cost minimization –Interface with special purpose logic; use of processor cores

Mark Franklin, S06 HLL (e.g., C, C++, Perl) vs Machine/Assembly Language (AL) HLL Pros: –Easier to express algorithms due to higher level constructs (e.g., For, Case, Arithmetic expressions, objects, etc.) –Type checking (Hardware for type checking ?). –Some memory allocation checking. Assembly Language Pros: –More control over ISA  more speed, less memory –More control over I/O Combination is often best for embedded systems: HLL calling AL.

Mark Franklin, S06 Example: HLL  AL Mapping b = c + d*e LOAD R1, d LOAD R2, e LOAD R3, c MPY R4, R2, R1 ADD R5, R4, R3 STORE R5, b HLL AL

Mark Franklin, S06 Buses: I A set of path(s) (wires) connecting on-chip or off-chip modules. –Serial bus: transmit one bit at a time –Parallel bus: transmits many bits simultaneously Generally time-shared. Generally has separate data & control paths. Typically has a separate bus controller or arbiter that decides which modules can use the bus at any given time.

Mark Franklin, S06 Buses: II Some common buses: –On-chip: AMBA, Wishbone, (generally not standard) –Off-chip: PCI Bus Family), bit transfer64bit transfer 33-MHz PCI133 MB/sec 266 MB/sec 66-MHz PCI266 MB/sec 532 MB/sec 100-MHz PCI-X MB/sec 133-MHz PCI-X GB/sec PCI-e(xpress) serial, 1 lane 500 MB/sec PCI-e(xpress) serial, 4 lanes 2 GB/sec –Off-chip: Other buses - SCSI, IDE, Infiniband Common issues: Arbitration, congestion. Logical equivalence between buses, multiplexers and switches.

Mark Franklin, S06 Bandwidth Requirements

Mark Franklin, S06 Bandwidth Trend

Mark Franklin, S06 Simple Queuing Theory View of Buses Bus is a shared resource and can be viewed as a server in a queuing system. Modules attached to the bus present inputs (i.e., requests) to the server (or Bus) and are queued up if the server is busy. BUS CPU I/O MemoryServer Queue

Mark Franklin, S06 Basic Queueing Theory Utilization: % time a server is busy Average Queue Length: Avg # of jobs in queue. Average System Delay (latency): Avg time from job entry into, to job departure from system. Arrival Time Distribution: Poisson Distribution of arrival times (exponential interarrival times). Service Time Distribution: Exponentially distributed service times. Queue Charactericstics: Infinite length; FIFO service discipline.

Mark Franklin, S06 Basic Queueing Results

Mark Franklin, S06 Basic Queueing Results M/M/1 Queue Length Waiting Time

Mark Franklin, S06 Computer Generations 1: Vacuum Tubes 2: Transistors 3: Integrated Circuit 4: LSI-Large Scale Integration; VLSI-Very LSI 5: ?? ULSI-Ultra LSI; parallel processing

Mark Franklin, S06 Technology: How we make a chip (roughly)

Mark Franklin, S06 Integrated Circuit Cost Cost.per.wafer Cost.per.die = (Dies.per.wafer) x (Yield) Wafer.area Dies.per.wafer = (approximate) Die.area 1 Yield = (empirical observation) (1 + (Defects.per.area)x(die.area/2)) 2 Typical: Die area = 1.5 cm x 1.5 cm; Wafer Diameter = 10 inches; Defects.per.cm 2 = 1.7; Yield = 50 %

Mark Franklin, S06 TECHNOLOGY TRENDS Semiconductors: –Transistor Density: +50%/year, quadruple in 4 years. –Die Size: %/year IC Logic Technology: –Transistors per Chip: %/year –Device Speed: +30%/year –Wire/Communications Speed: ~constant (Cu vs Al) Magnetic Disk Technology: –Density: % / year –Access Time: +35% / 10 years (8 ms).

Feature and Die Size

Mark Franklin, S06 Wafer Size 12-inch wafer

Mark Franklin, S06 SILICON & MAGNETIC DENSITIES

Mark Franklin, S06 Processor Performance Gains Performance (x VAX-10/780)

Mark Franklin, S06 Processor Cost Trends with Time

Mark Franklin, S06 SILICON & MAGNETIC DENSITIES