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Decoding Reel Strips

14 August 2006

By John Robison


I came across this web site selling old slot strips. I was wondering if you can perform some "fortune" telling and explain to us the deference's in the two strips.

  1. One has straight across winnings, and the other has patterns of /\ and \/ and -- for the Double Diamond Deluxe. (Could it be for the "Deluxe" part of the game having the Diamonds "fall or raise" into winning combinations?)
  2. How come on the Double Diamond strips the only visible win is the double bars. Could the strips have been cut funny? And should it look like the 5X pay strips, with equal wins or is for the programing of the Deluxe part again?
  3. How come on the middle strip of Double Diamond there are two triple bars and the first and third strips have only one triple bar? But, there is also an equal single chance for cherries or Double D's. Yet, the cherries and the 7,7,7 are spaced on the middle strip by 5 and 6 spots not next to each other. Why so far apart on the strip?
  4. I notice 11 spaces on a single strip for a "possible win". By having most (or should I say all) machines going to either video or server-based games, how will the player be able to see if there are actually 11 spots to win from, or will it really matter? A win will still be a win. It just matters how many coins you win and showing it on the reals.
  5. I also saw EPROM chips for Double Diamond for sale. They weren't official IGT. They had hit frequencies ranging from 76% all the way up to 98%. Is there this big a variety in the casinos?

This correspondent attached two JPGs of reel strips from two machines. One was a set of reels strips from a 5 Times Pay machine and the other a set of strips from Double Diamond Deluxe Quatermania machine. The diamonds pointing up or down are for the symbols that nudge to the payline, not necessarily into a winning combination.

  1. The reason the set from 5 Times Pay has straight across winning combinations is because all reel strips are the same. On the Quartermania set, the first and third strips are the same and the second is different.
  2. The layout of the symbols on the reel strips is completely irrelevant. The only thing that matters is the number of times each symbol appears on the virtual reels.
  3. The middle strip has one more triple bars symbol than the first and third strips because that's the way the designers laid out the strips. There might be a psychological effect that makes players think the triple bars are more likely on the second strip because it appears twice. But there might not be any reason for it. Again, the only thing that matters is the number of times each symbol appears on the virtual reels. There is nothing to be learned from the number of times symbols appear on the reel strips and the layout of the symbols on the strips.
  4. It doesn't matter today. Most reel strips today are half symbols, half blanks. But the virtual reels may be more than half blank, particularly the third reel.
  5. The numbers you quoted are long-term paybacks, not hit frequencies. Many machines do have such a wide range in long-term paybacks available for them. You might find the 76% payback at the Las Vegas airport, but competition usually keeps the lowest paybacks in casinos closer to 88%. Competition and statutory minimums. Also, all of the machines of a particular denomination in most casinos will have about the same long-term paybacks.

Best of luck in and out of the casinos,


My question is this, if the slot machine play outcome is controlled by the RNG, why do you see a pattern of payline combinations that repeat very consistently? For example, if you get two blue sevens (Red/White/Blue Slot) on the payline and the third blue seven drops below the payline you could reasonably bet the next spin will have a payline blank on the first position. You would think with the RNG that would not be true.

What's your opinion on this?


Dear Jim,

Two opinions.

First, I think it probably happens much less frequently than you think it does. If you kept careful track of your results, you might find that it doesn't happen consistently.

Second, let's assume that it does happen, say, 65% of the time. If 65% of the virtual stops on the first reel are blanks, then this is exactly what we would expect to happen. This is a lot of blanks for a first reel, so I think the most likely scenario is my first thought.

Best of luck in and out of the casinos,

Send your slot and video poker questions to John Robison, Slot Expert, at 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