The fashion for versions of slots with different RTPs must have come to online gambling from land-based casinos. Gambling specialist and founder of one of the most reputable gambling sites Wizard of Odds, Mike Shackleford, spoke about how casino managers change the RTP of land-based slots.
The interview dates back to 2012, so the information might be a little out of date, but he also talked about a new, remote way that is probably being practiced today. One of the questions was whether casinos can change settings remotely, and if they can do it while someone is playing for them. Here is what he replied:
Good question. What you are talking about is a technology known as Server Side Gaming. It worked and still works 99% of the time in Vegas, in such a way that when a casino manager wants to increase or decrease the return of a game, he must open the machine with a key and change the card, known as an EPROM. This means Erasable Programmable Read Only Memory.
He pulls out a more generous card and puts in a greedier one. He needs to literally open the machine and make changes. The manager is also required to fax the form to the Game Control Board, because the gaming police here in Nevada have a right to know what return every slot machine in the city is set to. And they actually do random inspections to make sure the casinos are giving them the correct information.
Now there is a new technology that saves casinos time. They no longer have to literally look for a key, open the device and change the recoil manually, now this can be done remotely, say, on a computer at the director's slot at the table. You might think that maybe he doesn't like me because of my polka-dotted hat, which he hates, so he will reduce the chances right when I play. Is he allowed to do this? No.
I don't know the exact specifics, but I think that the machine must be idle for a period of time without playing before the casino can change its return, for example, 15 minutes.
