IBM RT PC Options Installation page 228

3. Install the rear cover.
• On the IBM 6150 system unit, arrange the cables so that you
can fit the rear cover in place.
Warning: Do not operate the IBM 6150 system unit
for an extended period of time without the rear cover in
place. It is recommended that 75 mm (3 inches) minimum
clearance be provided between the IBM 6150 system unit
cover louvers and adjacent walls or furniture to ensure
adequate cooling.
9-4 Options Installation