Tascam MMR-8 User Manual
SCSI Tips for MMR/MMP Users
rev 1.0 1/26/99
3
SCSI Tips for MMR/MMP Users
We have found that the quality of materials and attention to detail in setting up external SCSI
devices for use with the MMR/MMP system can have a profound effect on the reliability and
performance of the system. This document provides details on some of the issues that have been
found to impact a successful and trouble-free installation.
devices for use with the MMR/MMP system can have a profound effect on the reliability and
performance of the system. This document provides details on some of the issues that have been
found to impact a successful and trouble-free installation.
SCSI Cables
There is a considerable difference in quality and performance of cables used to connect SCSI
devices. It is imperative that users pay close attention to this issue.
devices. It is imperative that users pay close attention to this issue.
Cable Quality
High quality SCSI cables are essential for proper MMR/MMP system performance. Low quality
cables, which are often thin, may cause data transmission errors, file corruption, and system
malfunctions. This is often due to improper and insufficient grounding, incorrect pin wiring, and
unwired pins. The following SCSI cable manufacturers are highly recommended as a source for
MMR/MMP SCSI cables:
cables, which are often thin, may cause data transmission errors, file corruption, and system
malfunctions. This is often due to improper and insufficient grounding, incorrect pin wiring, and
unwired pins. The following SCSI cable manufacturers are highly recommended as a source for
MMR/MMP SCSI cables:
Cable Length and Device Support
The MMR/MMP SCSI host card supports from one to eight SCSI devices. However when one to
four SCSI devices are connected, total cable length should not exceed three meters. When five to
eight SCSI devices are connected, total cable length should not exceed 1.5 meters. Note that total
cable length includes the internal cabling in carriers or drive bays. Thus if a 4-bay drive enclosure
contains ribbon cable internally that measures one meter in length, the external cable must not
exceed 2 meters. Improper cable length often causes an MMR system to freeze while mounting
volumes. (Note: Paralan can provide custom-length SCSI cables).
four SCSI devices are connected, total cable length should not exceed three meters. When five to
eight SCSI devices are connected, total cable length should not exceed 1.5 meters. Note that total
cable length includes the internal cabling in carriers or drive bays. Thus if a 4-bay drive enclosure
contains ribbon cable internally that measures one meter in length, the external cable must not
exceed 2 meters. Improper cable length often causes an MMR system to freeze while mounting
volumes. (Note: Paralan can provide custom-length SCSI cables).
Cabling Wide and Narrow Devices in a System
NARROW SCSI uses 8-bit data transfers. It generally uses a 50-pin connector.
WIDE SCSI uses 16-bit data transfers. It generally uses a 68-pin connector. Wide SCSI may also
refer to 32-bit SCSI data transfers but 32-bit wide SCSI is not as common.
Narrow drives should always be placed at the end of a SCSI chain. This is due to the fact that
when a Wide to Narrow connection is made, 8 bits are not passed through, so the Wide drive (and
all subsequent SCSI devices in the chain) receives only 8 bits of data instead of 16. If a Narrow
drive is connected after a Wide drive, the Wide drive still receives all 16 bits of data.
WIDE SCSI uses 16-bit data transfers. It generally uses a 68-pin connector. Wide SCSI may also
refer to 32-bit SCSI data transfers but 32-bit wide SCSI is not as common.
Narrow drives should always be placed at the end of a SCSI chain. This is due to the fact that
when a Wide to Narrow connection is made, 8 bits are not passed through, so the Wide drive (and
all subsequent SCSI devices in the chain) receives only 8 bits of data instead of 16. If a Narrow
drive is connected after a Wide drive, the Wide drive still receives all 16 bits of data.
Black Box Corporation -
www.blackbox.com
1000 Park Drive Lawrence, PA 15055-1018
Tel: 724-746-5500 || Fax: 724-746-0746
email
www.blackbox.com
1000 Park Drive Lawrence, PA 15055-1018
Tel: 724-746-5500 || Fax: 724-746-0746
info@blackbox.com
Paralan Corporation -
www.paralan.com
4655 Ruffner St., San Diego, CA 92111
Tel. (619) 560-7266 || Fax 619-560-8929
email: scsi@paralan.com
www.paralan.com
4655 Ruffner St., San Diego, CA 92111
Tel. (619) 560-7266 || Fax 619-560-8929
email: scsi@paralan.com