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SCSI Technology

SCSI Technology. Black Box Corp. Dave Mueller International Tech Support December 2000. History of SCSI. IBM-360 Selector Channel SASI 1979 Shugart Assoc. Systems Interface Scaled down version of the IBM Interface 1981Submitted to ANSI X3T9.2 committee SCSI X3.131-1986

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SCSI Technology

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  1. SCSI Technology Black Box Corp. Dave Mueller International Tech Support December 2000

  2. History of SCSI • IBM-360 Selector Channel • SASI • 1979 Shugart Assoc. Systems Interface • Scaled down version of the IBM Interface • 1981Submitted to ANSI X3T9.2 committee • SCSI • X3.131-1986 • Approved in 1986 BB Brasil Training December 2000

  3. SCSI Generations • SCSI 1 and SCSI 2 • Each version was a complete specification • Narrow bus, slow speeds • SCSI (formerly SCSI 3) • SPI SCSI Parallel Interface • A collection of standards • Wide bus on single connector, higher speeds • Makes older standards (SCSI 1, 2) and features (HVD) obsolete • SBP Serial Bus Protocol (IEEE1394) • FCP Fibre Channel Protocol (Fibre Channel) • SSA Serial Storage Architecture (IBM) BB Brasil Training December 2000

  4. SPI • SPI (SCSI-3) • 10MBps (narrow) or 20MBps (wide) • Ultra (Fast-20) is a half standard • Includes SPI but up to 20/40MBps (narrow/wide) • SPI-2 (Ultra2) • LVD, SCA-80, VHDCI • 20/40MBps • SPI-3 (Ultra3) • Makes HVD and dual-cable wide bus (SCSI2) obsolete • WIDE only • 160MBytes/sec • Many technical refinements (timing, command structure) BB Brasil Training December 2000

  5. Single Ended vs. Differential • Single Ended • Low cost • Short cable length • 1.5m @ 20 MBps, 3m @ 10 MBps, 6m @ 5 MBps • Most Common • Internal cables are flat ribbon • Differential • Expensive • Long cable lengths • HVD 25m at all speeds, LVD 12m at all speeds • Usually only on high end products (RAID array) • Internal cables must be flat twisted pair ribbon BB Brasil Training December 2000

  6. LVD vs. HVD • HVD • Originally in SCSI 1 (“differential”) • Defined in SCSI 2 as HVD • Made obsolete in SPI-3 • 25 Meters • LVD • Defined in SPI-2 • 12 meters • Backwards compatible with old SINGLE ENDED devices • Bus can only function in one mode, LVD (12m) or Single Ended (1.5/3/6m) • LVD Host adapter to legacy SCSI devices • If any device is legacy SCSI SE, then all LVD devices function as SE only BB Brasil Training December 2000

  7. STA Terms N O T E Bus Speed Mbytes/Sec Bus Width Bits Max Bus Length Meters (1) Maximum Devices Single Ended LVD HVD SCSI-1 2 5 8 6 (3) 25 8 Fast SCSI 2 10 8 3 (3) 25 8 Fast Wide SCSI 20 16 3 (3) 25 16 Ultra SCSI 2 20 8 1.5 (3) 25 8 Ultra SCSI 2 20 8 3 - - 8 Wide Ultra SCSI 40 16 - (3) 25 16 Wide Ultra SCSI 40 16 1.5 - - 8 Wide Ultra SCSI 40 16 3 - - 4 Ultra2 SCSI 2 40 8 (4) 12 25 8 Wide Ultra2 SCSI 80 16 (4) 12 25 16 Ultra3 SCSI 6 160 16 (4) 12 (5) 16 STA Terms BB Brasil Training December 2000

  8. Notes (1) The listed maximum bus lengths may be exceeded in Point-to-Point and engineered applications. (2) Use of the word "Narrow", preceding SCSI, Ultra SCSI, or Ultra2 SCSI is optional. (3) LVD was not defined in the original SCSI standards for this speed. If all devices on the bus support LVD, then 12-meters operation is possible at this speed. However, if any device on the bus is singled-ended only, then the entire bus switches to single-ended mode and the distances in the single-ended column apply. (4) Single-ended is not defined for speeds beyond Ultra. (5) HVD (Differential) is not defined for speeds beyond Ultra2. (6) After Ultra2 all new speeds are wide only. Chart and notes copied from SCSI Trade Association BB Brasil Training December 2000

  9. SCSI 1 • 5 MBytes/Second, 8 Bits wide • Electrical • Single Ended • Logic 1 = 0.0 to 0.5 VDC • Logic 0 = 2.5 to 5.25 VDC • Differential (HVD - High Voltage Differential) • Logic 1 = +Signal > -Signal • Logic 0 = -Signal < +Signal BB Brasil Training December 2000

  10. SCSI 1 Connectors • ‘A’ Cable • Alternative 1 • Unshielded 50 Pin, latches optional • Internal Ribbon, AMP-LATCH • Shielded 50 Pin (AMPMODU) • Alternative 2 • Shielded 50 Pin (External Telco, 50 pin Centronics, CHAMP) BB Brasil Training December 2000

  11. SCSI 2 • X3.131-1994 • Defines 8, 16 and 32 bit bus • Defines “Fast” SCSI for 10, 20 and 40 Mbytes/second • Adds the high density (.050 inch) 50 and 68 pin connectors BB Brasil Training December 2000

  12. SCSI 2 Connectors • ‘A’ Cable • Alternate 1 • Unshielded HD 50 pin, no hardware • Shielded HD 50 pin with latches • Alternate 2 • Unshielded LD, no hardware (50 pin ribbon) • Shielded LD with latches (50 Pin Centronics) BB Brasil Training December 2000

  13. SCSI 2 Connectors • ‘B’ Cable • Carries only high bytes • ‘A’ cable required for low bytes & termpwr • Unshielded HD 68 pin, no hardware • Shielded HD 68 pin, latches BB Brasil Training December 2000

  14. SCSI 3 • X3T10 Committee • A collection of substandards • SCSI Parallel Interface (SPI) • Extension of SCSI 2 • Serial • Fibre Channel • Serial Bus Protocol 2 (IEEE1394-1995) • IBM SSA (Serial Storage Architecture) BB Brasil Training December 2000

  15. SCSI 3 • Ultra2 and Wide Ultra2 • 40M and 80MByte/sec • Ultra3 • 160MByte/sec BB Brasil Training December 2000

  16. SCSI 3 Connectors • ‘P’ Cable • Unshielded HD 68 pin, no hardware • Shielded HD 68 pin, 2-56 screws • Carries control and 16 bits of data • ‘Q’ Cable • Same connectors as the ‘P’ Cable • Used for high bytes in 32 bit systems • ‘P’ cable required for low bytes & termpwr BB Brasil Training December 2000

  17. Interconnections • Narrow to Wide • Terminate high bytes • Do NOT mix single ended and differential • Do NOT mix HVD and LVD • Customer must know their application • See warning in AMP SCSI Guide BB Brasil Training December 2000

  18. SCSI Connectors • SCSI 1 • Internal: 50 Pin IDC Ribbon • External: Centronics • SCSI 2 • Includes SCSI 1 • Adds MD50 for external (MD for Micro D) • SCSI 3 • Includes SCSI 1 and 2 • Adds MD68 for external (screw locks) and internal (no locks) • SPI-2 • Adds VHDCI (Very High Density 68 pin) for external BB Brasil Training December 2000

  19. Black Box Products • Cables and Terminators • Dead-end and pass through • High Line • Active, passive, forced perfect • Differential ALWAYS passive, LVD is intelligent terminator • Adapters • Does customer need adapter or High Line Terminator? • Converters • SE to HVD, SE or HVD to Fiber Optic • Repeaters • Switches • Host Adapters • IC510C is ISA, all others are PCI BB Brasil Training December 2000

  20. Max Speed Mbytes/S SCSI SE/Diff Bus Width Ext Conn Int Conn IC510C 10 Fast SE 8 DB25 (Mac) IDC50 IC511C 10 Fast SE 8 MD50 IDC50 IC512C 20 Ultra SE 8 MD50 IDC50 IC513C 40 Wide Ultra SE 16 1xMD68 2xIDC50 2xMD68 IC514C 40 Wide Ultra SE 16 MD68 IDC50 MD68 IC515C 80 Ultra2 LVD 16 MD68 MD68 Host Adapters BB Brasil Training December 2000

  21. Web Sites • T10 Committee Website www.t10.org • SCSI Trade Association www.scsita.org • www.adaptec.com • www.amp.com • www.ancot.com • www.apcon.com • www.fibrechannel.com • www.paralan.com • www.timberconn.com • www.scsimasters.com BB Brasil Training December 2000

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