The following MCR instructions are supported to provide clock switching and MCR wait for interrupt compatibility with SA110 and SA1100 (StrongARM).

MCR     p15,0,Rd,c15,c1,2        ; Enable clock switching

This is equivalent to Asynchronous clocking mode.

MCR     p15,0,Rd,c15,c2,2        ; Disable clock switching 

This is equivalent to FastBus clocking mode.

MCR     p15,0,Rd,c15,c8,2        ; Wait for interrupt

This is equivalent to MCR p15,0,Rd,c7,c0,4.

These three MCR instructions must not be used and are deprecated in ARM architectures after v4T.