I have a 4000T and the user guide so I'll post the function of the dip switches.
Switch 1 - Set the SCSI address for the host adapter. The default is 7 with switches 1,2,3 set to "OFF".
Switch 4 - "OFF" indicates that the SCSI Fast Bus feature is enabled. Set this switch to ON if none of your SCSI devices supports SCSI Fast Bus.
Switch 5 - "OFF" indicates that your system uses the standard spinup (booting) time. Set this switch to "ON" to request a longer booting period.
Switch 6 - "OFF" indicates that the Synchronous Mode feature is enabled. Set this switch to "ON" to disable the synchronous mode.
Synchronous mode does not require acknowledgement for every byte transmitted, which can mean improved response time with most SCSI devices.
Switch 7 - "OFF" indicates that you do not have any external devices. This activates the terminator on the motherboard since this in one end of the SCSI bus.
Set this switch to "ON" when you install an external device, then set the external termination on the last device. This disables the terminator on the motherboard since it is now in the middle of the SCSI bus and not at the end.
Switch 8 - "OFF" indicates that only LUN 0 is recognized. Set this switch to "ON" to enable the system to recognize all LUNs.
Essentially you are okay with all switches OFF unless you have an external device connected when you should turn switch 7 to ON and terminate the last external device.
Hope this helps.
