LSI SYM22801 - Manual (Page 38)

2-24 Installing the SYM22801 Host Adapter
Four switches for each channel provide cable detection simulation and
forced upper line termination. Switch one simulates a device on the
internal 50-pin connector, switch two simulates a device on the internal
68-pin connector, switch three forces the upper SCSI line terminator to
stay on, and switch four simulates a device on the external 68-pin
connector.
When SYM22801 is in the middle of a bus using only one connector,
then switch Int68 and Ext68 (switches 2 and 4) for that bus are on. This
forces the terminators for that bus to be disabled.