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Ask the Slot Expert: Do machines that share progressives also share RNGs?

10 April 2019

Question: I regularly play at MGM National Harbor and noticed that there is often a "bank" of three to five similar machines which "share" progressive amounts. Recently while at the Borgata in Atlantic City I noticed that similar "banks" of machines are independent as to both progressives and red envelope values. This leads me to believe that the "connected" machines also share some RNG value. Can you clarify?

Also, I have noticed that some players remove their player's card during a bonus round. Does that mean that their "winnings" are not recorded on their card?

Answer: You really can't tell anything about how a machine determines its results based on whether it is a standalone progressive or whether it is linked with other machines to compete for the same progressives. Here in Nevada we have about 750 Megabucks machines that compete for the same Megabucks progressive around the state, we have banks of around four to eight machines that vie for one progressive, and we have machines that have their own private progressive — and these machines all have their own internal RNGs and determine their results completely independently of any other machine or system.

There's an interesting conversation that happens when a machine in a linked progressive hits the progressive. But first, a little background.

There's a computer called a progressive controller in a linked progressive system. The controller's job is to maintain the current value of the progressive and to communicate that value with all of the devices in the link. I say "devices" and not "slot machines" because there might also be one or more displays that show the value of the progressive(s).

When players play machines in the link, the machines send a message to the controller with the amount bet. The controller increases the progressive by the appropriate amount. The controller then sends a message with the new progressive amount to each device in the link.

The controller does not tell a machine to hit the progressive; the controller has nothing to do with determining outcomes. Each machine in the link determines its outcomes using its own RNG. When a machine hits the progressive, it sends a message to that effect to the controller. The controller then resets the progressive and sends a message with the new progressive value down the link.

There is a small delay between one machine's hitting the progressive and the other devices reverting to the reset amount. Nevada's regulations state that a player must be paid the progressive value displayed on the meter. Operators are not allowed to say that a player in another part of the casino, or another part of the state, hit the progressive first and the second player's display just hadn't been updated to show the reset amount yet.

For machines that are close to each other, the delay is a fraction of a second. For statewide links, it's long enough that an IGT speaker at a seminar I attended said that it's possible — really, really, REALLY unlikely, but possible — that a second player could hit the Megabucks before the reset message triggered by the first player to hit the Megabucks had propagated through the system. (Still, the delay is seconds. This seminar was many years ago, so the propagation delay could be much smaller today.)

So multiple machines competing for the same progressives doesn't tell us anything about how the machines determine their results.

To answer your second question, let's step into the Wayback Machine and go back about 20 years.

A video poker columnist in one of the gaming magazines teased his next column by saying that he would tell us when we should pull our players cards. The subject was not addressed in his next column. I saw him at an event a few months later and asked him about the missing information. He said that the column had been pulled.

Around the same time I attended a technical presentation about one of the popular slot club systems at the time.

At one time, players were able to pull their cards to prevent large wins from being reported to their accounts. Video poker players would sometimes pull their cards when dealt a royal or even a four-card royal just in case they completed the royal on the draw. The goal was to look like they had won less money than they actually had won.

This ploy worked many years ago. When you pull your slot club card, the slot club subsystem sends the current values of various meters to the slot club server so the database can record your play. In the early days of slot clubs, there was limited communication between the slot machine and the slot club subsystem. The subsystem did not know a play was in progress.

Today is a completely different story. The slot machine and slot club subsystem are integrated and there is a standard protocol for how the slot machine and slot club server communicate.

Have you ever tried to insert your slot club card in the middle of a video poker hand or bonus round? On a couple of occasions I have forgotten to put in my players card and tried to insert it in the middle of a play. The card reader displayed a cryptic message like "Session in progress," indicating that the slot club subsystem know that I was in the middle of a play and it was not going to accept the card now. I've never pulled my card in the middle of a play. But even if the display doesn't say, "You might think you're tricking the system by pulling your card now, but you're not", the machine can wait until the current play is over to send the card out message and meter values.


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