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Best of John Robison

Gaming Guru

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More on Slot Cycles

28 February 2005

John,

My wife and I like to play reel slots with a bonus round such as Elvis, Wheel of Fortune and most of all IGT's Pinball.

Two questions:

1. Are bonus round games programmed to hit the bonus symbol at some independent frequency, or is hitting the bonus symbol controlled by the RNG, just like any other possible symbol on the pay line?

2. Is a separate RNG used during the bonus round to control the possible payouts (since there are typically a smaller number of potential bonus round payouts than there are reel symbol combinations)?

Thanks,
Mike & Chris

Dear Mike & Chris,

The bonus symbol is just another symbol on the reels, as far as determining which symbols land on the payline is concerned. The program running the slot uses the output from the RNG to choose the stops on the reels that will land on the payline -- and if some of those symbols happen to be symbols that launch a bonus round, all the better for the player.

The frequency with which the bonus round occurs is determined solely by the number of times the bonus round symbols appear on the reels.

The same RNG is used to determine the results of bonus rounds. It's a piece of cake to convert random numbers from 1 to 1,000,000,000 to random numbers from 1 to 10.

Best of luck in and out of the casinos,
John


John,

I was told that the machine plays games when idle, and when a coin is inserted, it decided the outcome of the game before the second coin is inserted. I was also told that the manufacturers overlap the cycles thus preventing counting the number of games that are in a cycle. I also read that the RNG was like a string a lights, when you pushed the button and that combination is what you received. I was wondering if you could put to rest the theory of operation.

Thanks,
Kevin

Dear Kevin,

In the past, machines locked in the result of a spin when a coin was inserted. But anytime a machine is sitting with a result locked in, it is vulnerable to being cheated, so today's machines wait until the last possible moment to poll the RNG and lock in the result. It happens sometime after the player pulls the handle or hits the Spin button.

Machines do "play games" while idle. A more technical (and better) way to say that is to say that the RNG is constantly generating numbers, even while the machine is not being played.

Now, this business about cycles has to be one of the most misunderstood areas of slot operations. There are actually two cycles in the slot and many people just do not understand what the cycles are and why they're irrelevant.

One think sometimes referred to as a cycle is the total number of outcomes possible on the machine. This is found by multiplying together the number of stops on each reel. I read somewhere that some slot directors like machines with smaller cycles because they make the jackpots more likely to hit. Nonsense. The jackpot can hit with the same frequency on a machine with 2,000 stops and on a machine with 200,000 stops. It all depends on the number of times the jackpot symbol appears on the virtual reels.

The other cycle is the RNG's cycle or period. It tells how many numbers the RNG can generate before it starts repeating. This cycle, like the one before, is also mostly irrelevant.

Now, it is true the the RNG is really a psuedo-RNG. The numbers aren't truly generated at random. A deterministic function, which takes one or more prior results as parameters, is used to determine the next number. The numbers will come out in a definite pattern, and if you knew the pattern you could cheat the machine -- as cheats have done in the past.

Manufacturers have taken a number of steps to make RNG cheating very difficult. One we already mentioned, having the RNG run constantly. Another is a consequence of using more powerful processors in machines. RNGs can generate tens, hundreds, maybe even thousands of numbers per second. Even if you knew the jackpot was going to be the result in 2.53 seconds, it would be very difficult for you to start the spin while that is the result when results are only current for a fraction of a second.

Another anti-cheating step is to alter the speed at which the RNG runs. It may run in turbo mode for a few seconds and then fall back to turtle mode for a length of time. The last anti-cheating step I want to mention is periodically reseeding the RNG, that is, changing the parameters that are used as input to it. This has the effect of sending the RNG to a different point in its cycle.

And that brings us to an aspect of a cycle that we haven't discussed yet--moving predictably from one step to another, just as the minutes on a digital clock will predictably go from 00 to 59 and then repeat. I think that's what someone was referring to when he spoke of "overlapping cycles", but I really don't know what he meant. I don't know which cycles are supposed to be overlapped.

John


Send your slot and video poker questions to John Robison, Slot Expert, at slotexpert@comcast.net. Because of the volume of mail I receive, I regret that I can't send a reply to every question. Also be advised that it may take several months for your question to appear in my column.

John Robison

John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

Books by John Robison:

The Slot Expert's Guide to Playing Slots
John Robison
John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

Books by John Robison:

The Slot Expert's Guide to Playing Slots