Why do cpuinfo_cur_freq and /proc/cpuinfo report different numbers?

When I do

sudo watch -n1 cat /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_cur_freq

I get 1.8 - 2.7 GHz. It never goes above 2.7. And when I do

watch -n1 "cat /proc/cpuinfo | grep MHz"

I get 768 MHz - 1.8 GHz. It never goes above 1.8. Anyone know what is going on?