Based upon these latest comments, I decided to re-install a clean copy of Yosemite GM (previous version was an upgrade.)
My new clean install is still getting over 200k interrupts on ASPIPlatform.
	Code:
	    VECTOR  CPU#0   CPU#1   CPU#2   CPU#3   CPU#4   CPU#5   CPU#6   CPU#7   TOTAL   DEVNAME                 DRVNAME
    42      0       0       0       0       0       0       0       0       0       IPIC                           
    46      0       0       0       0       0       0       0       0       0       SMC                     com.apple.driver.AppleSMC
    48      0       0       0       0       0       0       0       0       0       RTC                     com.apple.driver.AppleRTC
    49      245413  0       0       0       0       0       0       0       245413  iMac12,2                com.apple.driver.AppleACPIPlatform
    4b      0       0       0       0       0       0       0       0       0       HPET                    com.apple.driver.AppleHPET
    4c      0       0       0       0       0       0       0       0       0       HPET                    com.apple.driver.AppleHPET