Bus structures : Bus structures Unit objectives
Describe the primary types of buses, and define interrupt, IRQ, I/O address, DMA, and base memory address
Describe the features and functions of the PCI bus
Describe the features and functions of the various video buses
Topic A : Topic A Topic A: Buses
Topic B: The PCI bus
Topic C: Video buses
Buses : Buses Communication pathway
Defined by
How many bits it transmits at one time
Signaling technique
Data transfer speed
Four types
Address
Data
Expansion
Video continued
Buses, continued : Buses, continued Address and data buses enable:
Basic CPU operation
Interactions with memory
Expansion bus
Communication pathway for non-core components to interact with core components
Adapter cards add functionality
PCI bus predominant
Older buses: ISA, EISA, Micro Channel, and PC bus
PCI bus slots : PCI bus slots
Video bus : Video bus Generates signals sent to monitor
Can be built into motherboard or adapter card
Communicates over expansion or video bus
Enormous amount of data strains expansion bus
Graphic buses
VESA or AGP
Transmit video data at high speeds
An AGP video bus slot : An AGP video bus slot AGP slot
The riser bus : The riser bus Brings the basic wiring and control of a function to a motherboard
Decreases cost
Three riser standards:
Advanced Communication Riser (ACR)
Audio/Modem Riser (AMR)
Communication and Networking Riser (CNR)
Activity A-1 : Activity A-1 Examining buses
System interaction : System interaction Gain the attention of the CPU
Access shared memory locations
Extend the system BIOS
Transfer data across the bus
Interrupts : Interrupts Signal CPU that attention is needed
CPU stops what it was doing
Services the device request
Returns to its previous task
Polling
Inefficient alternative to interrupts
IRQs : IRQs Numerical addresses
Help CPU identify interrupt source
Enforce priority of interrupts
Common IRQs
IRQ 1: Keyboard
IRQ2: Cascade IRQs 9-15
IRQ4: COM1
IRQ6: Floppy
IRQ12: PS/2 mouse
IRQ14: Primary IDE hard drive
Device Manager: IRQs : Device Manager: IRQs
Activity A-2 : Activity A-2 Examining IRQ assignments
I/O addresses : I/O addresses Identify section of shared memory
Range of memory addresses
Hexadecimal
Device Manager: I/O addresses : Device Manager: I/O addresses
Activity A-3 : Activity A-3 Viewing your computer’s I/O address assignments
DMA channels : DMA channels DMA controller relieves CPU
Dedicated channels
Largely replaced by other techniques, such as bus mastering
Device Manager: DMA channels : Device Manager: DMA channels
Activity A-4 : Activity A-4 Viewing your computer’sDMA channel assignments
Base memory addresses : Base memory addresses Devices extend system BIOS with new routines
Display adapters
SCSI controllers
IDE controllers
System BIOS locates and loads BIOS extensions using mapped memory location
Device Manager: Base memory : Device Manager: Base memory
Activity A-5 : Activity A-5 Viewing your computer’s base memory address assignments
Topic B : Topic B Topic A: Buses
Topic B: The PCI bus
Topic C: Video buses
Bus types : Bus types PCI currently most popular
Historical bus types
PC/XT
PC/AT
ISA
EISA
MCA
PC/XT bus : PC/XT bus 8-bit bus
IBM PC and IBM XT
4.77 MHz clock speed
1.6 Mbps maximum data transfer rate (0.4 MBps)
Supported IRQs 0-8
Configured with DIP switches or jumpers
PC/XT card : PC/XT card
PC/AT and ISA bus : PC/AT and ISA bus 16-bit bus
IBM AT, clones, 80386/486, current PCs
8 MHz clock speed
8 MBps maximum data transfer rate
ISA adapter : ISA adapter
ISA expansion bus slot : ISA expansion bus slot
PCI bus : PCI bus 32- or 64-bit bus
Pentium PCs
33 or 66 MHz clock speed
133-533 MBps maximum data transfer rate
Up to 8 functions on a single card
Up to 5 cards/slots per system
Requires PnP
PCI adapter : PCI adapter
PCI slots : PCI slots
PCIe : PCIe Newer standard
Uses serial communication
Link
Lanes
x1 (by one)
x1, x2, x4, x8, x12, x16, and x32 bus widths
Can up-plug
Can’t down-plug
Multifunction cards : Multifunction cards PCI spec supports multifunction cards
Up to 8 functions per card
Five slots/cards per system
Total of 40 expansion devices
Activity B-1 : Activity B-1 Identifying a PCI bus
Topic C : Topic C Topic A: Buses
Topic B: The PCI bus
Topic C: Video buses
Need for video buses : Need for video buses Older PC designs just used expansion bus
Graphical interfaces involve massive amounts of graphics data
Specialized buses were developed to be fast enough
VESA local bus : VESA local bus 32- or 64-bit bus
Pentium PCs
33 or 66 MHz clock speed
Popular on 80486-based PCs
Generally software configurable
No longer used
VLB adapter : VLB adapter
PCI-based video : PCI-based video Low-end systems: video adapter built into motherboard
Three type of video slots
PCI
PCIe
AGP
PCI is slowest of three types
Share bus with all other PCI-based devices
Work well for two-monitor system
AGP standards : AGP standards AGP 1.0
AGP 2.0
AGP 3.0
64-bit AGP
Ultra-AGP
AGP Pro
Ultra-AGPII
AGP : AGP Technically a port, not a bus
Provides direct connection between video adapter and CPU
Referred to as #X
Original performance benefit was accessing and using main system memory
Direct Memory Execute (DIME)
Modern AGP cards use onboard memory, except in laptops
Multiple-monitor support
Being phased out for PCIe
AGP adapter : AGP adapter Note the hook
AGP characteristics : AGP characteristics 32-bit bus
Multiple of 33 MHz clock speed
Speed “pumped” to as much as 533 MHz
266-2133 MBps maximum data transfer rate
PnP configurable
AGP slots : AGP slots Typically brown; sometimes maroon or other dark color
Separated from other bus slots
High-end systems include multiple, independent AGP slots
An AGP slot : An AGP slot
PCIe : PCIe 16x PCIe card has 4 Gbps bandwidth
Dual line technology allows up to 8 GBps
Simultaneous data movement upstream and downstream
Ideal for gaming and photography, videography
A PCIe video card : A PCIe video card
Activity C-1 : Activity C-1 Identifying graphics connections
Unit summary : Unit summary Described the primary types of buses, and defined interrupt, IRQ, I/O address, DMA, and base memory address
Described the features and functions of the PCI bus
Described the features and functions of the various video buses, and installed and configured an AGP adapter card