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Introducing the 16-Bit UltraSCSI Hub (Rack-Mountable)
This chapter gives a brief physical description and describes the functions and functional specifications of the DWZZH-S5 and DWZZH-09 UltraSCSI Hubs.
The series of DWZZH Hubs are SCSI–2 and draft SCSI–3 (ANSI X379.2/91– 10R3) compliant capable with data transfer rates of up to 40 Mbytes per second. The two versions of these Hubs are:
∙DWZZH-S5: A shelf-contained, rack-mountable, 5.25" SBB (large) Hub with four host ports and one storage port, all differential. See Figure 1–1.
∙DWZZH-09:A shelf-contained, rack-mountable Hub consisting of two 5.25" SBBs (large) with eight host ports and one storage port, all differential. See Figure 1–2.
1.1 UltraSCSI Hub Features
Most device SCSI buses are either 8-bit or 16-bit single-ended, physical buses. Some controllers and hosts use differential buses and others use a single-ended bus. Single-ended and differential physical buses are not compatible. The UltraSCSI protocol disables both buses when they are connected together. By using an UltraSCSI Hub you can accomplish the following:
∙Provide radial disconnect where remaining connections can continue to operate.
∙Provide fair SCSI arbitration for host nodes (DWZZH-05, -S5 and the -09 UltraSCSI Hubs only).