2.2.4 CPC drawer power 2.3 Single chip modules Each CPC drawer gets its power from two DCAs. The DCAs provide the required power for  the drawer in an  n +1 configuration. Loss of one DCA leaves enough power to meet power  requirements for the entire drawer. The DCAs can be concurrently serviced and are accessed  from the rear of the frame A. Figure 2-12 shows the location of DCAs on the backplane of the A frame. The single chip module (SCM) is a multi-layer metal substrate module that holds one PU chip  or an SC chip. Both CP and SC chip size is 696 mm$^{2}$ (25.3 mm x 27.5 mm). Each CPC  drawer has six (model M01-M04) or seven SCMs (model M05), five or six PU SCMs (6.1  billion transistors each), and one SC SCM (9.7 billion transistors).  Chapter 2. Central processor complex hardware components  47 2 DCA Fans N+1 Blowers 2 DCA Fans DCA Power Supplies behind the fans 2 DCA Fans 2 DCA Fans 2 DCA Fans 2 DCA Fans 2 DCA Fans 2 DCA Fans Figure 2-12 DCA power supplies