= AST RESEARCH, INC. TECHNICAL BULLETIN # 1142 4-14-95 = ENSURING PROPER SCSI TERMINATION This is an informational bulletin. Manhattan servers use a SCSI disk sub-system, which must be correctly terminated at each of its ends. Termination must only be installed at each end of the SCSI bus. All devices in the middle of the SCSI bus must have their termination disabled/removed . The following provides an overview of the termination required for various AST Manhattan Servers. The configurations are assumed to be using internal SCSI subsystems only. NOTE: For all configurations, any device attached in the middle of the SCSI bus (between the terminator on the SCSI backplane and the terminator on the system board) must have its termination removed/disabled. 1) In an AST Manhattan P system, the termination is built into both the system board and the SCSI backplane. 2) In an AST Manhattan V system, the termination is built into the system board. The termination on the last device on the SCSI bus must be enabled. 3) In an AST Manhattan SMP system, the termination is built into the Empire-5 DAC and a terminator (167300-003) must be installed on the SCSI backplane. 4) In an AST Manhattan G system, the termination is built into the NCR PCI SCSI II controller. The termination on the last device must be enabled. For other configurations please refer to the system documentation. When a SCSI disk sub-system is incorrectly terminated, the sub-system may fail. Failures can include: drives intermittently dropping off-line; data-corruption on the hard drives; and duplicated or shadowed drives. These problems can be caused by either a lack of termination, incorrectly placed termination, or over termination of the sub-system. An example of an incorrectly terminated SCSI sub-system would be one in which all hard drives have termination enabled. In this case, the drives may been seen by the controller, and be configurable, but they may drop off-line intermittently. Due to the complexity of SCSI disk sub-systems, a termination tester is available from the vendor listed below. The tester is plugged into an external SCSI port (or cable attached to the system board or SCSI backplane), and will indicate whether the SCSI bus is properly terminated, unterminated, or over-terminated. This testing should be performed on any system that exhibits problems, such as those described in this bulletin. WARNING: Before performing any tests to the system, ensure that all data has been backed up and all configuration settings have been recorded. Changes made to the SCSI bus or termination could result in the loss of data, configuration information, or RAID settings on the hard drives. The tester does not operate as a terminator and does not determine the location of the terminators found. The system should not be operated while the tester is installed. In addition to the Termination Tester, a cable is required on some systems to attach the tester to the system. To use the tester with a Manhattan Server, you should follow these guidelines: A) For Manhattan P/V using embedded NCR controller: Use cable Part Number 501623-001 - External cable connection kit. This kit contains a cable (AST P/N 221344-001), which attaches to the external SCSI controller connector on the system board (location J56B or J57B). The Tester is then attached to the external cable connection (at the end of the newly added cable). To test the system, termination must be disabled in System Setup before testing, and if required re-enabled after testing. B) For Manhattan P/V using DPT PCI Disk Array Controller: No cable is necessary to use the tester. The tester is attached to the external SCSI II port on the DPT PCI controller. To test the system, termination must be disabled in the DAC configuration utility (accessed using during a boot) before testing, and if required re-enabled after testing. NOTE: This method will only test the first SCSI Channel. To test the second channel, follow warnings above, and move drives from the second to the first channel, and then perform the termination testing. C) For Manhattan SMP using Mylex DAC 960 Controller: Use cable kit Part Number 501622-001 - External cable connection kit. The kit contains a 50 pin SCSI cable (AST P/N 221383-001) which can be attached to the SCSI backplane. Follow warnings above before testing. The backplane terminator (167300-003) should be removed, and the external cable attached to the backplane in its place. The Termination Tester can then be attached to the end of the cable for testing. D) For Manhattan G using the NCR PCI SCSI II controller: No cable is necessary to use the tester. T he tester is attached to the external SCSI II port on the NCR PCI SCSI II controller. To test the system, termination must be disabled on the NCR PCI SCSI II controller before testing, and if required re-enabled after testing. E) For Manhattan XP No cable is necessary to use the tester. Remove the external SCSI cable attached to the SCSI II port on the back of the Manhattan XP and attach the Tester to the Manhattan XP external SCSI II port. SCSI TERMINATION TESTER VENDOR: METHODE ELECTRONICS - DATAMATE VENDOR PART NUMBER: DMTT - 50HD VENDOR DESCRIPTION: SCSI SINGLE-ENDED 50 POSITION TERMINATION TESTER CONTACT INFORMATION: Call 1-800-323-6858 or 708-867-9600 Corporate Headquarters: 7444 West Wilson Avenue Chicago, IL 60656 Methode-Electronics - Datamate has international subsidiaries in many countries. Refer to your local directory assistance, or call the number above for a referral to your nearest international distributor.