University of Pune S.E. I.T. Subject code: 214442

Computer Organization

Part 34 : PCI and SCSI Buses

UNIT V Tushar B. Kute, Department of Information Technology, Sandip Institute of Technology & Research Centre, Nashik. http://tusharkute.com

Standard I/O Interfaces Traditional (ISA) (with cache)

High Performance PCI Bus

Peripheral Component Interconnect In early 1992, the Intel formed an another industrial group in relation to the PC bus. The main objective behind the formation of the group was to overcome the weakness in ISA and EISA buses. They designed the PCI specifications in June 1992 and updated in April 1993.

Features Requires very few chips to implement. Uses the to increase the bus clock speed. Ability to function with 64-bit data bus. High bandwidth, 33 MHz. Support of single and multiprocessor systems. Operate concurrently with the processor bus. Function as mezzanine or peripheral bus. Synchronous timings. Better system performance for high speed I/O subsystems such as AGP, NIC, disk controllers. Plug and Play. PCI in single processor system

PCI in multi processor system PCI Connector

PCI Bus Lines (required)

Systems lines Including clock and reset Address & Data 32 time mux lines for address/data Interrupt & validate lines Interface Control Arbitration Not shared Direct connection to PCI bus arbiter Error lines PCI Bus Lines (Optional)

Interrupt lines Not shared Cache support 64-bit Bus Extension Additional 32 lines Time multiplexed 2 lines to enable devices to agree to use 64-bit transfer JTAG/Boundary Scan For testing procedures

PCI Commands

Transaction between initiator (master) and target Master claims bus Determine type of transaction e.g. I/O read/write Address phase One or more data phases PCI Read Timing Diagram

PCI Bus Arbiter PCI Bus Arbitration

SCSI

Small Computer System Interface, or SCSI (pronounced scuzzy), is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners and CD drives.

Background SCSI was derived from "SASI", the "Shugart Associates System Interface", developed c. 1978 and publicly disclosed in 1981.[2] A SASI controller provided a bridge between a 's low- level interface and a host computer, which needed to read blocks of data. Larry Boucher is considered to be the "father" of SASI and SCSI due to his pioneering work first at Shugart Associates and then at Adaptec. Dal Allan pronounced the new acronym as "scuzzy" and that stuck.

SCSI Interface SCSI Interface

SCSI Controller SCSI-1

This was evolved from SASI in 1979. it was approved by ANSI in 1986 as X3.131-1986. SCSI defines the basis for first SCSI buses including cable length, signaling features, command and transfer modes. It uses only a 8-bit bus, with 5 MB/s data transfer rate.

SCSI-2

The extension of original SCSI approved by ANSI in 1994 and released as X3.131-1994. Fast SCSI, 10 MHz, 10 MB/s, 8bit regular SCSI. Wide SCSI, 16/32 bits. More devices per bus: 16 Improved cable and connectors (50 in SCSI-1) Active termination. Differential Signaling, to allow long cable lengths. Command Queuing: allow multiple requests on the bus Additional Command Set: for CDROMs, Scanner

SCSI-3

Devised in 1993. Known as SCSI-3 parallel interface SPI. It defines mechanical, electrical protocol layers of the interface. Data transfer rate: 8-bits at 20 MB/s over 50 pin connector. 16-bits at 40 MB/s over 68 pin connector. The capabilities of IEEE-1394 and Fiber Channel were included.

SCSI Speeds SCSI Bus termination

Passive Termination Active Termination Forced Perfect Termination High Voltage Differential Low Voltage Differential

Data transfer on SCSI bus

Initiator Target SCSI Bus Signals

References

Websites: http://en.wikipedia.org Computer Architecture and Organization By A. P. Godse (from books.google.com ) Computer Organization By Hamacher and Zaky