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Best of John Robison
More "truth" about slots21 July 2008
It is rare in life that two people can make opposing statements and both be right. In your last statement you mention machines in England.
In what country were the machines that you analyzed? I'm writing strictly about games in the United States and not about games in any other country. Other countries may have rules that differ from those here in the United States. For example, a former co-worker told me he had a friend who develops a particular piece of software for fruit machines in England. This particular piece of software was designed to keep a machine's actual payback within a specific range. If the firmware you analyzed and reports you monitored were for non-U.S. machines, we can both be right.
Let me further clarify my position by stating that most of my articles describe Class III slot machines. The piece of software I described in the preceding paragraph is illegal in a Class III slot machine in the United States.
I have not developed any slot firmware myself, but I have acted as an expert witness in patent disputes. As an expert witness, I've had access to source code, depositions and testimony.
How can you have a "true RNG" with 90% payback? RNGs do not have paybacks. They just generate a stream of numbers.
Here is how a Class III slot machine operates in the U.S.:
Let's assume we have a 3-reel machine with 32 virtual stops and 22 physical stops on each reel.
Hundreds, if not thousands, of times each second, the slot's operating system calls the RNG function to generate another number. This occurs all the time, even when the machine is not being played. Thus the vast majority of the numbers produced by the RNG are never used to determine the outcome of the spinning reels. The RNG stores the number it generates in a specific memory location.
When the player initiates a game by pressing the Spin button, the program "polls the RNG" to find out the most recently generated number. It reads the number stored in that specific memory location.
Most machines poll the RNG for each reel, so this number will be used to determine where only the first reel will stop. The range of the numbers produced by the RNG is probably larger than the number of virtual stops on the virtual reel, so we have to MOD the number down to the proper range. In this case we'll MOD 32 to get a number from 0 to 31. That's the virtual stop chosen on the first reel.
Now that we know the virtual stop, we have to look at the virtual reel layout to see which physical stop is mapped to this virtual stop. The program then stops the stepper motor on the first reel on that physical stop.
The RNG has continued to generate numbers while this was going on. Now it's time to poll the RNG to get a result for the second reel. The number we get from this poll is again MODded to the proper range. The program checks the virtual reel layout for the second reel to find out which physical stop should land on the payline. It then stops the stepper motor on the second reel on that physical stop.
The process is repeated for the third reel.
The RNG generated hundreds of numbers while this spin was playing out. Only three of them were used to determine the outcome of the spin.
We calculate a machine's hit frequency by looking at each winning combination and seeing how many ways we can make the combination based on the layout of the symbols on the virtual reels. For example, if there are three triple bars on the first and second reels, and only two on the third, there are 3 x 3 x 2 or 18 ways to hit triple bars. Add up all the ways to make all the winning combinations and divide by the total number of combinations on the virtual reels to get the hit frequency.
To find the one-coin long-term payback, we build on the work we did calculating the hit frequency. Take the number of ways to hit each winning combination and multiply it by the value of the combination when playing one coin. Add up all those products and divide by the total number of combinations to get the one-coin long term payback.
To find the payback when playing other than one coin, the value used in the multiplication is the value used when playing that number of coins. We also have to divide by the number of coins played too.
U.S. machines do not have two virtual reel layouts, a losing layout and a winning layout. The RNGs do not change their "bitedness" based on past spins.
U.S. machines rely on nothing but the principles of Random Sampling with Replacement to guarantee that in the long run a machine's actual payback will be very close to the payback calculated from the layout of the symbols on the virtual reels. Slot regulations in the U.S. require that the outcome determined by the RNG must be displayed.
It's possible that a machine can show a loss for a while after it is put on the casino floor. It's even possible for a machine to hit the jackpot on the very first pull after it's put on the slot floor. As the machine gets more play, its actual payback will tend to get closer and closer to its calculated payback.
Best of luck in and out of the casinos,
Send your slot and video poker questions to John Robison, Slot Expert, at firstname.lastname@example.org. Because of the volume of mail I receive, I regret that I can't reply to every question.
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