PDP-8 on FPGA project & where is Hans Pufal?

My solution in the emulator is to compute the ratio of on/off over that 1/60th of a second and then use that to display an image of a lamp. Actually, I go one better than that. I have a simple first order time constant model of the lamp so that it doesn't go from 0->100% in 1/60th of a second. new_intensity = K*old_intensity + (1-K)*new_duty_cycle. Pick K to approximate the thermal inertia of the lamp. Oh, to keep from having to compute a tally of all the lamps after each instruction simulation cycle, I have an array of 256 counters for each byte of address or data bus. So for a given byte, after each instruction I just do: histo[byte_value]++. At the time it comes to display each lamp, I look at all the buckets and figure out the average duty cycle for each of the 8 lamps in the group.