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The Expansion Bus. Three Tasks A card needs to be built specifically for the expansion slot – the right signals at the right place. Connectivity Card.

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Presentation on theme: "The Expansion Bus. Three Tasks A card needs to be built specifically for the expansion slot – the right signals at the right place. Connectivity Card."— Presentation transcript:

1 The Expansion Bus

2 Three Tasks A card needs to be built specifically for the expansion slot – the right signals at the right place. Connectivity Card needs some way to communicate with the CPU – in and out. Communication Operating System needs some way to allow user to control the device/card. Drivers

3 Structure Expansion bus(es) connect to the chipset And PCIe



6 Speed CPU (and Northbridge) tied to System Crystal Almost all chips/devices have clock wire for timing This could lead to lots of devices at each specific speed (66, 100, 133, etc.) Solution is to add an Expansion Crystal for consistent timing on the bus

7 Expansion Crystal

8 Errata to Book Figure 8-5 shows Expansion Crystal connected to CPU. That is not correct. Expansion Crystal should connect to Sound Card and Modem Card (which figure does not show)

9 PC Bus Was an 8-bit bus (match to EDB) Ran at about 7 MHz Had patents, but no licensing fees Did not, of itself, create clone market as Michael suggests. Also did not mess with Apple as he suggests

10 PC Bus

11 286 at 16 bits Need to improve on 8-bit expansion bus Just extend the bus to add more bits Still running at 7 MHz

12 System Resources I/O Resources IRQs DMA channels Memory Addresses Our life today, with Plug and Play (PnP), takes care of most of this for us

13 I/O Addresses Input/Output Port Addresses Use the IO/MEM wire with addresses CPU Device We use hex notation, using four hex digits. Range is 0000 to FFFF Not every device has four I/O addresses; some have more, some less

14 I/O Addresses for Devices Digging into Device Manager:

15 Rules of I/O Addressing All devices have at least one I/O address Most devices use more than one address (system speaker only uses one) No two devices can share the same I/O address The first address in the range is often called the Base Address, 01F0h for hard disk drive

16 I/O Addresses to Know 03F8COM1 O2F8COM2 03E8COM3 O2E8COM4 0378LPT1

17 Interrupt Requests (IRQs) We need a way to start communication with the CPU from the device We use Interruption, much like a ringing telephone Interrupts are CPUDevice I/O Advanced Programmable Interrupt Controller (IOAPIC)


19 IRQ Rules Almost every device needs an IRQ (joystick does not use one) Mostly, cant share an IRQ (modem/fax can) Many IRQs are allocated to devices through a table of standard values

20 Unused IRQs are not listed here

21 Preset Assignments PortBase Address IRQ COM13F84 COM22F83 COM33E84 COM42E83 LPT13787

22 Direct Memory Access (DMA) Most of the time, the CPU is busy and much of the system is idle CPU uses EDB about 5 percent of the time Some devices can access memory directly without the CPUs help Sound cards, floppy drives and hard disk drives use DMA Used a very simple, extra CPU with DMA Request, or Channel wires

23 Limits to DMA Designed for PC bus, limited to 7 MHz Can only handle 8-bit data streams per chip Cascading chips allow for 16-bit transfers Now used for low-speed data transfers: floppy drive (DRQ2), sound and tape backup Today we have Bus Mastering; the device takes (intelligent) control and skips the DMA chip giving us Ultra DMA

24 Memory Addresses Option ROM (from previous week) on the card needs memory address space Usually allocated from near the top of first meg of RAM (Upper Memory) Devices can not share memory Ranges can not overlap Fully automatic today

25 New Expansion Bus 16-bit bus only ran at 7 MHz and was limited to 16 bits at a time We had to manually assign System Resources to each card We needed improved technology and a way to go faster

26 False starts – Part 1 IBM and Microchannel Architecture (MCA) – first 32-bit bus Smarter bus – could allocate System Resources Required personality disk to install or remove – giant hassle over floppies Heavily patented and expensive licenses Used on PS/2 line (87-88) from IBM



29 Spin Doctors Industry (and consumers) resisted MCA Manufactures argued for Return to Industry Standard Architecture or ISA Bus (ii-sa) 1987-1988 time frame 1/2

30 False starts – Part 2 EISA bus (ee-sa) Used a double-deep slot; top part for ISA cards and lower, 32-bit slot for EISA cards Lasted almost a year ISA contacts here EISA contacts here



33 False starts – Part 3 Video Electronics Standards Association created the VESA local bus (VL-bus) 32-bits total (16+16); connected at Front Side Bus; ran at 33 MHz Glue on to ISA bus


35 Enter PCI Intel gets credit for this one (1993) Peripheral Component Interconnect 32-bit, 33 MHz; mezzanine bus as it sits between FSB and rest of expansion bus (ISA) Self-configuring (PnP), allows Ultra-DMA (bus mastering) Uses sharable Interrupt Channels (INTA, INTB, C and D) Supports I/O addresses above 3F8 to FFFF

36 Honorable Mention to AGP Video demands keep pushing bus improvements Accelerated Graphics Port PCI slot with its own connection to Northbridge This, and more, when we do Video chapter 20



39 PCI - X PCI Extended 64-bit slot for servers, Mac G5 Four speeds: 66, 133, 266 and 533. 266 is double-pumped 133; 533 is quad-pumped. Not going to see this on the desktop.

40 PCI Express PCIe –xN. PCI express by N (some number of lanes wide). About 2004-5 Serial connection (differential signals) Not a shared bus like all before it; each connection direct to Northbridge chip

41 Installing Expansion Cards Need to know that the card works with OS and motherboard Insert card properly – dont break things and beware of ESD Provide drivers – specific to card and OS Verify proper operation

42 Installation Order Most video cards today require that you –uninstall current video drivers (revert back to generic Microsoft driver) – install new driver software –Remove old card and install new card –Finish (driver) installation Always read installation instructions first

43 Will it work? Will it work with your motherboard? –Cant install PCIe-x16 video card in AGP slot –Cant install ISA sound card in PCI-only m/b Will it work with your OS? -This will be an issue for Windows 7 (?) -Always an issue with new OS Is device on the Hardware Compatibility List (HCL) or Windows Marketplace?

44 Physical Installation Do you have an available slot? Beware ESD Beware the 5v on the motherboard – pull the plug during installation Handle the card carefully – dont get wet fingerprints on connector. Insert, and remove, card at a slight angle Install the attachment screw before you power up the system

45 Handle card

46 Preventative Maintenance Dont use pencil eraser to clean contacts, rather, use canned contact cleaner – but only if card has had a long shelf life. Sometimes removing and reseating a card a time or two will bring the card back to life. The attachment screw WILL line up with hole if you have installed card correctly 10

47 Drivers Expansion cards WILL have a floppy/CD with driver(s) in the box. Read the directions to determine whats first: device install or driver install Video cards usually need old (card) drivers removed first; usually in Add/Remove Programs Remove All-In-One printer controls from Add or Remove Programs too.

48 More Drivers A lot of drivers are unsigned – usually means they did not pay Microsoft to test the driver. Its not as scary as it looks. If you have to force the Add Hardware Wizard you probably did something wrong 64-bit Vista and 7 require driver signing

49 Verify Operation Dont leave until you have verified operation of the expansion card. Device Manager is a good place to check after install and driver install Have the device do its something just to make sure all is well (and client is happy) 7

50 Plug and Play (Pray) Need a PnP BIOS – standard issue since about 1997 Need a PnP OS – Windows 9x and up, not DOS or Windows 3.x Need a PnP device/card – all new (PCI and up) cards are PnP. Some ISA cards were also. Not marked on box anymore. 6

51 How PnP works PnP devices told to be quiet BIOS searches for legacy devices and assigns resources PnP devices announce usable resources BIOS allocates resources to PnP card(s) This happens each time you boot system and occurs prior to beep. 5

52 ESCD BIOS keeps list of devices in Extended System Configuration Data list Usually, at boot, this list is checked against installed hardware and if they match, the allocation process is skipped 4

53 IRQ Steering PCI devices use dynamically assigned interrupt channels rather than IRQs. Sometimes we have to make it appear that device is using IRQ; often we stack devices on single IRQ. The BIOS sorts all this out and will switch resources for a legacy program. 3

54 Trouble - Visable Device Manager error indicators: –Yellow circle with black exclamation point usually means driver is damaged –Red X symbol means device is disabled and not working –Yellow question mark is found device but lacking correct driver(s). 2

55 1

56 Trouble – Not Visible Windows should recognize new card on bootup and ask for driver(s). If it does not ask, you (or card) failed some step. USB devices should be recognized on connection. Drivers, drivers, drivers Get an account at 0


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