LSI 21003 - Manual (Page 36)

2-20 Installing the LSI21003
2.2.4.4 Internal and External SCSI Connections
If internal and external SCSI devices are connected to the host adapter,
then terminate the last internal and external devices on the SCSI bus.
You must disable the termination on all other devices. Termination on
Channel A of the host adapter is automatically disabled in this case.
Figure 2.15 shows an example of how termination is determined for this
SCSI bus configuration on the host adapter internal Channel A and
external Channel A.