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Ask the Slot Expert: How do video poker machines deal cards?3 April 2013
Thanks for the kind words about my columns.
As you said, the chances of being dealt a royal flush are 4 out of 2,598,960 or 1 out of 649,740. That's easy.
It's harder to figure out the chances of drawing to a royal flush. It's relatively easy to figure out the chances when you hold 1 card to the royal, 2 cards, 3 cards, 4 cards and 0 cards. But that's only half the problem. We also have to figure out the chances of holding a 1-card royal, a 2-card royal, etc. Those calculations depend on your strategy, which depends on which paytable you're playing. I don't know those things, so we're stuck.
Fortunately, there is an estimate I can give you. As a general rule, you hit royal flushes about once every 40,000 hands. Some strategies may hit royal flushes a little more frequently, others a little less. But 1 in 40,000 is a good, general estimate.
Moving on to your second question, video poker machines used to select all ten cards that could be required to play out a hand at once when you pressed the Deal button. Five cards were revealed, and then something had to be done with the five remaining cards.
One choice is to keep the cards in a stack, like you would at your kitchen table. When the program needed to replace a discard, it would take the top card off the stack. This is known as a "serial" deal.
The other choice is to assign each card to a particular location, so card 6 is conceptually hiding behind card 1, to be revealed only if card 1 is discarded. This is known as a "parallel" deal.
Which method do today's machines use? Neither. Today's machines choose the five cards to be dealt, and then continue electronically shuffling the deck and choose the cards to replace the discarded cards only after the Draw button has been pressed. Today's machines do not sit with cards already selected because that makes the machines vulnerable to being cheated.
A group in the Midwest was able to figure out the RNG function in a video poker machine and, with that information, they were able to figure out the five cards that would be used to replace discards. Obviously, they were caught.
Usually, whether an older machine used a parallel or serial deal was irrelevant. The player odds are the same. But there was one incident in which the type of deal did make a difference.
The hold buttons on a machine malfunctioned and a card that a player wanted to hold wasn't held. I don't remember the exact details and I couldn't find a report of the incident online, so let's say the player had a 4-card royal in the first four cards dealt and held only three of the cards due to the malfunction. Then the card needed to complete the royal appeared in the spot for the card that should have been held.
If the machine used a parallel deal, then the player would not have completed the royal flush. The card needed would not have been revealed because the player did not discard the card above it. If the machine used a serial deal, however, the player would have completed the royal. The card needed would have been sitting on top of the draw pile and would have replaced the card in position 5, thus completing the royal.
Moving on to your last question, when you play a multi-hand machine, the cards you hold and discard are removed from all of the decks and then cards to replace your discards are drawn at random from each deck.
Royal flushes for all,
Send your slot and video poker questions to John Robison, Slot Expert™, at email@example.com. Because of the volume of mail I receive, I regret that I can't reply to every question.
Best of John Robison