There are LVD/SE and HVD cards and drives (HVD are also called just differential since it was the first standard). Connecting HVD to a mac will cause a drive shutdown or magic smoke.
Anyway a 7100 is a Nubus machine with built in 50 pin SCSI. Unless you have a Nubus SCSI card I will assume you are just using the built in 50 pin connector.
The problem with SCA drives is they have no built in termination so you must terminate them on the cable or on the drive at the end of the cable. On the 7100 the SCSI CDROM should have a termination jumper so you are in luck. Now you need a SCA to 50 pin adapter or a SCA to 68 pin adapter and a 50 to 68 pin converter. The hard drive has to be able to go into SE mode otherwise it will not work.
Anyway a 7100 is a Nubus machine with built in 50 pin SCSI. Unless you have a Nubus SCSI card I will assume you are just using the built in 50 pin connector.
The problem with SCA drives is they have no built in termination so you must terminate them on the cable or on the drive at the end of the cable. On the 7100 the SCSI CDROM should have a termination jumper so you are in luck. Now you need a SCA to 50 pin adapter or a SCA to 68 pin adapter and a 50 to 68 pin converter. The hard drive has to be able to go into SE mode otherwise it will not work.