CONFIG_TIMER_ACORN is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_TIMER_ACORN (not configurable)

modulename: time-acorn.ko

configname: CONFIG_TIMER_ACORN

Linux Kernel Configuration
└─>TIMER_ACORN
In linux kernel since version 2.6.12  
source code:
arch/arm/common/time-acorn.c