DayStar Digital confirmed that Apple Tape Backup does not run with cache turned
on. The only current workaround (June, 1990) is to turn the cache off when
running Tape Backup.
Please note that removing the DayStar FastCache Macintosh IIci CDEV will not
turn cache off, since it is controlled in ROM. The correct way is to leave the
DayStar CDEV in the System Folder, choose Control Panel from the Apple menu,
click the DayStar FastCache Macintosh IIci CDEV, and turn the cache off.