IBM RT PC Options Installation page 57

Installing a Fixed-Disk Drive in Position D
Warning: Handle the fixed-disk drive carefully. Dropping, shaking,
or rough handling can damage both the drive and any stored data and
can cancel the warranty.
The fixed-disk drive types installed in drive positions C and D
MUST
be the same drive type. The drives will not operate correctly if drive
types are mixed.
Refer to the system unit diagram for a picture of drive position D.
Refer to "Handling Static-Sensitive Drives" on page 2-4 before beginning
this section.
Warning: Follow all instructions under "Removing the Covers From
the System Units" on page 1-4 before installing the second drive.
2-20 Options Installation