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SCSI

SCSI. SCSI Hard Drives. SCSI Hard Drives. SCSI drives are faster. More expensive. Require a separate host adapter. Connect in a daisy-chain. Allows multiple drives from a single host adapter using a single PCI bus slot and a single IRQ. Allows multiple commands. Motherboard. ATA Drives.

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SCSI

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  1. SCSI

  2. SCSI Hard Drives

  3. SCSI Hard Drives • SCSI drives are faster. • More expensive. • Require a separate host adapter. • Connect in a daisy-chain. • Allows multiple drives from a single host adapter using a single PCI bus slot and a single IRQ. • Allows multiple commands.

  4. Motherboard ATA Drives Slave Master

  5. Motherboard ATA Drives Secondary Slave Primary Slave Secondary Master Primary Master

  6. Motherboard SCSI Drives SCSI Host Adapter

  7. Internal SCSI Interface Cable To Host Adapter To SCSI Drives

  8. Internal SCSI Interface Cable

  9. Motherboard SCSI Drives SCSI Host Adapter Terminators

  10. Motherboard SCSI Drives SCSI Host Adapter SCSI Controller

  11. Connecting External SCSI Devices SCSI Connectors Terminator IN IN IN OUT OUT OUT From SCSI Host Adapter SCSI Device SCSI Device SCSI Device

  12. Adding a SCSI Device Terminator IN IN IN IN OUT OUT OUT OUT From SCSI Host Adapter SCSI Device SCSI Device SCSI Device SCSI Device New Device

  13. SCSI Host Adapter Internal External

  14. Internal SCSI Peripheral #1 External SCSI Peripheral #1 Host Adapter Two Internal and Two External SCSI Peripherals Internal SCSI Peripheral #2 External SCSI Peripheral # 2 Terminator Terminator

  15. Bus Width 8-bits (1 byte) Data Transfer Rate 5 MB/s Devices supported 8 SCSI-1

  16. SCSI-1 Terminator SCSI Cables Terminator 4 7 6 5 1 2 0 3 Host Adapter SCSI Peripheral Devices

  17. SCSI-2 • Fast SCSI • Fast Wide SCSI

  18. Bus Width 8-bits (1 byte) Data Transfer Rate 10 MB/s Devices supported 8 Fast SCSI

  19. Bus Width 16-bit (2 bytes) Data Transfer Rate 20 MB/s Devices supported 16 Fast Wide SCSI

  20. SCSI-3 • SPI-1 Ultra and Wide Ultra • SPI-2 Ultra2 and Wide Ultra2 • SPI-3 Ultra3 or Ultra 160 • SPI-4 Ultra 320 • SPI-5 Ultra 640

  21. SPI-1 • Ultra SCSI (Sometimes called Narrow Ultra SCSI or Fast-20 SCSI) • Wide Ultra SCSI

  22. Bus Width 8-bit Data Transfer Rate 20 MB/s Devices supported 8 Ultra SCSI

  23. Bus Width 16-bit Data Transfer Rate 40 MB/s Devices supported 16 Wide Ultra SCSI

  24. SPI-2 • Ultra2 SCSI (Sometimes called Fast-40 SCSI or Ultra-40 SCSI) • Wide Ultra2 SCSI (Sometimes called Ultra-80

  25. Bus Width 8-bit Data Transfer Rate 40 MB/s Devices supported 8 Ultra2 SCSI

  26. Bus Width 16-bit Data Transfer Rate 80 MB/s Devices supported 16 Wide Ultra2 SCSI

  27. Bus Width 16-bit Data Transfer Rate 160 MB/s Devices supported 16 SPI-3Ultra3 SCSI or Ultra-160 SCSI

  28. Bus Width 16-bit Data Transfer Rate 320 MB/s Devices supported 16 SPI-4Ultra-320 SCSI

  29. Bus Width 16-bit Data Transfer Rate 640 MB/s Devices supported 16 SPI-5Ultra-640 SCSI

  30. Ultra640 SCSI Ultra320 SCSI Ultra160 SCSI Wide Ultra2 SCSI Ultra2 SCSI Ultra SCSI Wide Ultra SCSI Fast SCSI Fast Wide SCSI SCSI 10 20 40 80 160 320 640 5 Time Data Transfer Rates (Megabytes per second)

  31. Ultra640 SCSI SPI-5 Ultra320 SCSI SPI-4 Ultra160 SCSI SPI-3 Time Wide Ultra2 SCSI Ultra2 SCSI SPI-2 Ultra SCSI Wide Ultra SCSI SCSI-3 SPI-1 Fast SCSI Fast Wide SCSI SCSI-2 SCSI-1 10MB 20MB 40MB 80MB 160MB 320MB 640MB 5MB Data Transfer Rates

  32. Narrow SCSI is 8-bits wide and accommodates 8 devices. • Wide SCSI is 16-bits wide and accommodates 16 devices.

  33. One of the devices is always the SCSI host adaptor. Terminator Terminator SCSI Host Adapter 3 0 1 2 6 5 7 4

  34. Terminator Terminator SCSI Host Adapter 2 1 3 0 6 5 7 4 Disabled Terminator

  35. Passive SCSI Terminators TERMPWR 220-Ohm Resistor SCSI Bus Line 330-Ohm Resistor

  36. Active SCSI Terminator Voltage Regulator TERMPWR 2.8V SCSI Bus Line 110-Ohm Resistor

  37. Forced Perfect Termination (FPT) • A variation of active termination. • Includes clamping diodes. • Eliminates signal undershoot and overshoot. • Contributes to longer cable lengths.

  38. SCSI Addressing Scheme or SCSI IDs • 8 devices numbered 0 through 7 • 16 devices numbered 0 through 15

  39. SCSI Priority • A kind of “pecking order” to determine which device gets first shot at using the SCSI bus. • Determined by the SCSI ID.

  40. The SCSI ID determines the priority of the SCSI device. 7 6 5 4 3 2 1 0 Highest Priority Lowest Priority

  41. SCSI ID determines priority Terminator Terminator 4 7 6 5 1 2 0 3 Host Adapter SCSI Devices

  42. Customary SCSI IDs • SCSI Host Adapter ID 7 • Primary Hard Drive ID 0

  43. SCSI Priority Narrow SCSI 7 6 5 4 3 2 1 0 Lowest Highest Wide SCSI 7 6 5 4 3 2 1 0 15 14 13 12 11 10 9 8 Highest Lowest

  44. SCSI Bus Arbitration • Device waits for bus to become free. • Device signals its intention to use the bus, indicating its address. • If a second device attempts to use the bus at the same time, the device with the higher priority wins.

  45. Setting the SCSI ID • Each SCSI device must have a unique ID. • The SCSI ID is set when a new SCSI device is installed. • The SCSI Host Adapter should be given SCSI ID 7. • May be set by hardware or in software.

  46. Setting the SCSI ID 0 1 7 6 2 5 3 4 Slide Switches Rotary Switch Jumpers

  47. Setting the SCSI ID with Jumpers 1 2 3 0 4 5 6 7

  48. IDE SCSI Wide SCSI

  49. Logical Unit Number (LUN) • A sub-level addressing scheme. • Each SCSI ID can have up to 8 LUN addresses. • Narrow SCSI allows 7 SCSI IDs times 8 LUN addresses for 56 attached devices. • Wide SCSI allows 15 SCSI IDs times 8 LUN addresses for 120 attached devices.

  50. SCSI ID 0 SCSI ID 1 SCSI ID 2 LUN0 LUN0 LUN1 LUN1 LUN2 LUN2 LUN3 LUN3 SCSI IDs and LUNs

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