Configuration Note; Maximum Allowable Cable Distances - Compaq S5 User Manual

DWZZH 16–Bit UltraSCSI Hub (Rack-Mountable)
2.2

Configuration Note

According to the UltraSCSI Configuration Guidelines (included in your
purchase), the maximum allowable cable distance for an UltraSCSI Domain is 74
meters. Each element, including the DWZZH-09 has an associated relative cable
distance value associated. Cables count as their specified distance, (including the
0.5 meter jumper cable between the SBB Hubs); but each DWZZH SBB counts
as an 18.5 meter cable equivalent. This means that communications from a
server attached to the left-hand SBB to a server attached to the right-hand SBB,
already has a 37.5 meter cable equivalent distance cost to propagate the signal
through the DWZZH-09 Hub. Therefore, if the distance from server A to the Hub
is X, and the distance from server B to the Hub is Y, then the sum cable distance
of X and Y must be less than or equal to 36.5 meters (74 – 37.5). Please note that
any SCSI transaction from a host to the storage subsystem only propagates
through one of the SBBs. This means that you may still have a cable length of 25
meters between the storage subsystem and the DS-DWZZH-09. Refer to Figure
2–4.
Figure 2–4 Maximum Allowable Cable Distances
2–4 EK–SMDZS–UG. B01