Seagate ST136403LW/LC Data bus widths, Providing adequate cooling, SE and LVD bus configurations

12 Cheetah 36 Installation Guide, Rev. A

Data bus widths

These drives have a wide (16-bit) SCSI data bus. You can use these drives on a non-wide (8-bit) data bus if you provide proper termination to the upper eight data lines. This is often referred to as providing “high-9 termination” (the other bit is for parity).

The following table lists the maximum cable lengths and number of devices using single-ended and LVD I/O circuits.

Table 1.	SE and LVD bus configurations
SCSI		Maximum
		number of
driver	I/O transfer rate		Maximum cable
		devices on
type	(Mbytes/s)		length allowed
		bus
SE	20	16	6 meters (19.7 ft.)
SE	40	4	3 meters (9.8 ft.)
SE	40	8	1.5 meters (4.9 ft.)
LVD	80	16	12 meters (39.4 ft.)

Providing adequate cooling

The enclosure design must ensure adequate cooling for the drive. The maximum ambient temperature allowed is 50°C.

The drive’s product manual (83329440) describes how to evalu- ate the air-flow design. The evaluation consists of ensuring that the case temperature of certain critical components remains within acceptable limits during drive operation.

Figure 2 shows two design approaches with one or more fans used to generate air flow. The air-flow patterns can be created