Specifications

Pro Tools|HD Getting Started Guide66
SCSI Cables
Use shorter SCSI cables to improve reliability.
Table 1 provides guidelines for maximum cable
lengths according to SCSI type.
In the following table, the maximum cable
length includes all cables used in the chain, not
just point-to-point connections.
Distribute Audio Across Multiple Drives
For best recording and playback performance,
don’t record and play back all audio files in a ses-
sion from the same drive. Instead, use Pro Tools
Disk Allocation features to distribute audio files
between multiple drives. See the Pro Tools Refer-
ence Guide for details.
Separate Video and Audio Files
If you are working with QuickTime, movie files
must reside on a different SCSI bus than audio
files. If audio files reside on disks connected to a
SCSI HBA card, video data should reside on
drives connected to a different SCSI bus.
Dual-Channel SCSI HBA Cards
If you use a dual-channel SCSI HBA card, allo-
cate audio files equally to drives connected to
each of the two busses on the card for optimal
performance.
If using video files, make sure to put your video
files on one bus and audio files on the other bus.
Connecting SCSI Drives
To connect an external SCSI drive:
1 Turn off power to both the computer and the
hard drive.
2 Attach a SCSI cable from the SCSI port of the
hard drive to the SCSI port of the SCSI HBA card
or computer.
3 Secure the cable’s connectors to the hard drive
and computer.
4 Connect additional drives by daisy-chaining
from one drive to another. Keep cable lengths to
a minimum (see Table 1).
Table 1: Maximum cable length and number of drives
supported according to SCSI type
SCSI Type and
Transfer Rate
Maximum
Cable Length
Maximum
Number of
Drives
Fast SCSI
10 MB/sec
3 meters 8
Wide SCSI
20 MB/sec
3 meters 16
Ultra SCSI
20 MB/sec
(8-bit narrow)
3 meters 5
Ultra SCSI
40 MB/sec
(16-bit wide)
3 meters 5
Ultra SCSI
20 MB/sec
(8-bit narrow)
1.5 meters 6–8
Ultra SCSI
40 MB/sec
(16-bit wide)
1.5 meters 6–8
Ultra1 SCSI
Low Voltage
Differential (LVD)
160 MB/sec
12 meters 16
Ultra2 SCSI
Low Voltage
Differential (LVD)
80 MB/sec
12 meters 16
Ultra3 SCSI
Low Voltage
Differential (LVD)
320 MB/sec
12 meters 16