Input/Output Organization III: Commercial Bus Standards
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Transcript of Input/Output Organization III: Commercial Bus Standards
Input/Output Organization III: Commercial Bus Standards
CE 140 A1/A220 August 2003
Bus
Pathways of interconnections between different computer components
Three general types; data, address, control
Bus characteristics
Bus width – how many bits can be transmitted at a time
Bus speed – how many bits can be transmitted across each wire per second
Bus bandwidth – bus width x bus speed (same as maximum throughput)
IBM PC/XT Bus
Used on 8088-based systems 8-bit bus Copied by clone vendors for
compatibility with third-party I/O boards
IBM PC/XT Bus
Source: Phil Storrs PC Hardware book <http://members.iweb.net.au/~pstorr/pcbook/showtell/show2.htm>
IBM PC/AT Bus
Used on the 80286-based PC/AT Maintained compatibility with the XT
bus Added an edge connector to increase
bus width to 16-bits
ISA
Industry Standard Architecture Same as the PC/AT Bus 16-bit, 8.33 MHz Maximum
throughput 16.7 MB/s Limited bus master support
ISA
Source:<http://www.rackmountnet.com/ipc/isa_bk/isa_bk.htm>
Problems with ISA
Slow Limited number of interrupts Lack of bus master support Specific to Intel architecture cards
built using ISA will not work on non-Intel platforms
IBM-specific problem: no more monopoly on the hardware market
MCA (IBM’s response) MicroChannel Architecture Developed by IBM for the PS/2 line 16-bit/32-bit computer bus 10-16 MHz Intended to replace the ISA bus Allows bus mastering Limited plug and play Limited to IBM hardware Incompatible with XT, ISA boards
EISA (Industry’s response)
Extended Industry Standard Architecture
Extends ISA bus to 32 bits Maximum throughput: 33.3 MB/s Increased bus mastering support Maintains compatibility with old ISA
boards
EISA
Source:<http://www.atmarkit.co.jp/fpc/slotsocket/indexpage/>
Need for a faster bus
Original IBM PC: text-based applications
Advent of GUIs (Windows, et al) demand high performance
Need for a faster bus
Example 1024 x 768 display 24-bit color 30 frames per second 67.5 MiB/s ISA: 16.7 MB/s EISA: 33.3 MB/s
Local Bus Concept
Demand for higher bandwidth and increased throughput
Bus placed near (or on) the processor’s memory bus
“Local” to the processor Does not have to go through the
slower ISA bus
VESA Local Bus
Developed by Video Electronics Standards Association (VESA)
High-speed conduit for memory-mapped I/O and DMA
Intended for high-bandwidth peripherals (video, storage, etc.)
33 MHz, 32-bit Extension of the 486 memory bus
VESA Local Bus
Source:<http://www.lco-college.edu/classes/pc-ware/chap4b.html>
PCI
Peripheral Component Interconnect (PCI)
Developed by Intel (90’s) but standard was made public platform independent
33 Mhz, 32-bit Maximum throughput 132 MB/s
Plug-and-Play
PCI
Source:<http://www.ontrack.com/hardwareinfo/input-output.asp>
PCI Variants
PCI 2.2: 64-bit, 66 Mhz Maximum throughput: 533 MB/s
PCI-X: 64-bit, 133 Mhz 1066 MB/s PCI-X 266 (PCI-X DDR) 2133 MB/s PCI-X 533 4 GB/s Mini PCI – small form factor PCI cards
for use with embedded systems/portable systems
Problem with using PCI alone
Still not fast enough for memory Not compatible with ISA cards
Intel’s Solution: Northbridge/Southbridge Architecture
Uses bridge chips PCI Bridge (Northbridge)
Connects CPU, memory, and PCI bus ISA Bridge (Southbridge)
Connects PCI bus to the ISA BUS and also supports one or two ATA disks
Advantage: High-bandwidth memory bus (Front Side Bus) PCI bus available for high-bandwidth peripherals
Next generation: Intel Hub Architecture
Northbridge/Southbridge Architecture
Source: Structured Computer Organization by Tanenbaum
AGP
Accelerated Graphics Port High-speed computer bus designed
for 3D computer graphics acceleration
AGP 1X: 32-bit, 66 MHz Also available: 2X, 4X, 8X
AGP
Source: http://www.watch.impress.co.jp/pc/docs/article/991008/hotrev30.htm
PCI-Express
Next generation PCI implementation from Intel
Intended to replace AGP and PCI altogether
Not fast enough as a memory bus Alternatives: HyperTransport
SCSI Small Computer Systems Interface Pronounced “scuzzy” Higher transfer rate than ATA disks Used in workstations and servers More than just a hard disk interface, a full-
fledged bus Also supports CD-ROMs, CD-recorders,
scanners, tape units, etc. Devices are daisy-chained in a linear
manner Terminated at the end to prevent reflection
SCSI TypesName Data Bits Bus MHZ MB/sec
SCSI-1 8 5 5
Fast SCSI 8 10 10
Wide Fast SCSI
16 10 20
Ultra SCSI 8 20 20
Wide Ultra SCSI
16 20 0
Ultra2 SCSI 8 40 40
Wide Ultra2 SCSI
16 40 80
SCSI Typical 8-bit SCSI cable
50 wires, 25 ground, 8 for data, 1 for parity, 9 for control
IEEE 1394 Developed primarily by Apple Commonly referred to as Firewire (Apple),
i.Link (Sony) or digital video (DV) port Used for data storage devices and digital
video cameras Does not require a host IEEE 1394a: up to 400 Mbps IEEE 1394b: up to 800 Mbps Allows daisy-chaining, plug-and-play, and
hot-swapping
USB Universal Serial Bus Developed as a replacement to the serial
and parallel ports USB 1.1 – Up to 12 Mbps USB 2.0 – Up to 480 Mbps Up to 127 devices (THEORETICAL!) Daisy-chained in a tree structure Requires a host computer Upcoming: USB On the Go
Storage Interfaces
ATA Serial ATA SCSI IEEE 1394 USB
ATA
Advanced Technology Attachment Standard interface for connecting
storage devices Transitioned from PIO to DMA modes With the advent of Serial ATA, it has
been retroactively renamed Parallel ATA
ATA Types
Most new drives support Ultra DMA Modes (in contrast to Programmed I/O modes)
Ultra ATA/33 – 33 MBps Ultra ATA/66 – 66 MBps Ultra ATA/100 – 100 MBps Ultra ATA/133 – 133 MBps
ATA-VI
Supports 48-bit addressing that allows system to address 144 PB
Breaks the 137 GB size barrier imposed by older ATA standard
ATA Cables
Serial ATA
Higher speed than Parallel ATA Hot-swappable Cable: 7-wire cable versus 40/80-wire
cable Power cable: 15 pins Initial speed: 150 MBps Later implementations: 300 MBps,
600 MBps
Serial ATA Cables