Slide 1OutlineBuses in a PC: connect a few devices (2002)Main components of Intel Chipset: Pentium II/IIIA Three-Bus System (+ backside cache)What is DMA (Direct Memory Access)?Slide 7Why Networks?How Big is the Network (1999)?Growth RatesWhat makes networks work?Typical Types of NetworksABCs of Networks: 2 ComputersA Simple Example: 2 ComputersQuestions About Simple ExampleABCs: many computersSlide 17Slide 18Observations About Simple ExampleSoftware Protocol to Send and ReceiveProtocol for Networks of Networks?Protocol Family ConceptSlide 23Protocol for Network of NetworksTCP/IP packet, Ethernet packet, protocolsOverhead vs. BandwidthShared vs. Switched Based NetworksNetwork SummarySlide 29Magnetic DisksPhoto of Disk Head, Arm, ActuatorDisk Device TerminologyDisk Device PerformanceData Rate: Inner vs. Outer TracksDisk Performance Model /TrendsDisk History (IBM)Disk HistoryModern Disks: Barracuda 7200.7 (2004)Modern Disks: Mini DisksModern Disks: 1 inch disk drive!Modern Disks: << 1 inch disk drive!Magnetic Disk SummaryCS 61C L26 Disks & Networks (1)A Carle, Summer 2005 © UCB inst.eecs.berkeley.edu/~cs61c/su05 CS61C : Machine StructuresLecture #26: Disks & Networks 2005-08-04Andy CarleCS 61C L26 Disks & Networks (2)A Carle, Summer 2005 © UCBOutline•Buses•Networks•DisksCS 61C L26 Disks & Networks (3)A Carle, Summer 2005 © UCBBuses in a PC: connect a few devices (2002)CPUMemory bus (FSB)MemorySCSI:External I/O bus(1 to 15 disks)SCSI InterfaceEthernet InterfaceEthernet Local Area Network•Data rates (P4)•Memory: 400 MHz, 8 bytes 3.2 GB/s (peak)•PCI: 100 MHz, 8 bytes wide 0.8 GB/s (peak)•SCSI: “Ultra4” (160 MHz), “Wide” (2 bytes) 0.3 GB/s (peak)GigabitEthernet: 0.125 GB/s (peak)PCI InterfacePCI: Internal(Backplane) I/O busBus - shared medium of communication that can connect to many devices. Hierarchy!!CS 61C L26 Disks & Networks (4)A Carle, Summer 2005 © UCBMain components of Intel Chipset: Pentium II/III•Northbridge:•Handles memory•Graphics•Southbridge: I/O•PCI bus•Disk controllers•USB controlers•Audio•Serial I/O•Interrupt controller•TimersCS 61C L26 Disks & Networks (5)A Carle, Summer 2005 © UCBA Three-Bus System (+ backside cache)•A small number of backplane buses tap into the processor-memory bus•FSB bus is only used for processor-memory traffic•I/O buses are connected to the backplane bus (PCI)•Advantage: load on the FSB is greatly reducedProcessor MemoryProcessor Memory Bus (FSB)BusAdaptorBusAdaptorBusAdaptorI/O BusBacksideCache busI/O BusL2 CacheBackplaneCS 61C L26 Disks & Networks (6)A Carle, Summer 2005 © UCBWhat is DMA (Direct Memory Access)?•Typical I/O devices must transfer large amounts of data to memory of processor:•Disk must transfer complete block •Large packets from network•Regions of frame buffer•DMA gives external device ability to access memory directly: •much lower overhead than having processor request one word at a time.•Issue: Cache coherence:•What if I/O devices write data that is currently in processor Cache? -The processor may never see new data!•Solutions: -Flush cache on every I/O operation (expensive)-Have hardware invalidate cache lines (“Coherence” cache misses?)?CS 61C L26 Disks & Networks (7)A Carle, Summer 2005 © UCBOutline•Buses•Networks•DisksCS 61C L26 Disks & Networks (8)A Carle, Summer 2005 © UCBWhy Networks?•Originally sharing I/O devices between computers (e.g., printers)•Then Communicating between computers (e.g, file transfer protocol)•Then Communicating between people (e.g., email)•Then Communicating between networks of computers p2p File sharing, WWW, …CS 61C L26 Disks & Networks (9)A Carle, Summer 2005 © UCBHow Big is the Network (1999)?Computers in 271 Sodain inst.cs.berkeley.eduin eecs&cs .berkeley.eduin berkeley.eduin .edu in US(.com .net .edu .mil .us .org)in the worldSource: Internet Software Consortium~30~400~4,000~50,000~5,000,000~46,000,000~56,000,000CS 61C L26 Disks & Networks (10)A Carle, Summer 2005 © UCBGrowth RatesEthernet Bandwidth1983 3 mb/s1990 10 mb/s1997 100 mb/s1999 1000 mb/s2004 10 Gig E010,000,00020,000,00030,000,00040,000,00050,000,00060,000,00070,000,00080,000,00090,000,000100,000,000Jan-93 Apr-95 Jun-97 Aug-99 Internet Hosts "Source: Internet Software Consortium (http://www.isc.org/)".CS 61C L26 Disks & Networks (11)A Carle, Summer 2005 © UCBWhat makes networks work?•links connecting switches to each other and to computers or devicesComputernetworkinterfaceswitchswitchswitch•ability to name the components and to route packets of information - messages - from a source to a destination•Layering, protocols, and encapsulation as means of abstraction (61C big idea)CS 61C L26 Disks & Networks (12)A Carle, Summer 2005 © UCBTypical Types of Networks•Local Area Network (Ethernet)•Inside a building: Up to 1 km•(peak) Data Rate: 10 Mbits/sec, 100 Mbits /sec,10Gbits/sec (1.25, 12.5, 1250 MBytes/s)•Run, installed by network administrators•Wide Area Network•Across a continent (10km to 10000 km)•(peak) Data Rate: 1.5 Mb/s to >10000 Mb/s•Run, installed by telecommunications companies (Sprint, UUNet[MCI], AT&T)• Wireless NetworksCS 61C L26 Disks & Networks (13)A Carle, Summer 2005 © UCBABCs of Networks: 2 Computers•Starting Point: Send bits between 2 computers•Queue (First In First Out) on each end•Can send both ways (“Full Duplex”)•Information sent called a “message”•Note: Messages also called packetsnetworkinterfacedeviceOSapplnOSapplnCS 61C L26 Disks & Networks (14)A Carle, Summer 2005 © UCBA Simple Example: 2 Computers•What is Message Format?•Similar idea to Instruction Format•Fixed size? Number bits?•Header(Trailer): information to deliver message•Payload: data in message•What can be in the data?•anything that you can represent as bits•values, chars, commands, addresses...8 bit32 x Length bitsDataLengthCS 61C L26 Disks & Networks (15)A Carle, Summer 2005 © UCBQuestions About Simple Example•What if more than 2 computers want to communicate?•Need computer “address field” in packet to know which computer should receive it (destination), and to which computer it came from for reply (source) [just like envelopes!]8 bits32xn bits8 bits 8 bitsHeader PayloadCMD/ Address /DataNet ID Net IDDest. SourceLenCS 61C L26 Disks & Networks (16)A Carle, Summer 2005 © UCBABCs: many computers•switches and routers interpret the header in
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