em_ghetto_realtime.rb

require 'eventmachine'
require 'benchmark'

x = 0

t = Benchmark.realtime do
  EM.run do
    EM.add_timer(1.5) { raise "OMG" }

    time = EM.current_time + 0.002

    EM.add_periodic_timer(0) do
      if EM.current_time >= time
        x += 1
        time += 0.002
        EM.stop if x == 512
      end
    end
  end
end

puts t
puts x

# $ ruby em_ghetto_realtime.rb
# 1.0243961811065674
# 512