How are video poker hands dealt? - Mitchell Tsai from Bookmarklet

In Video Poker Mania, Dwight Crevelt says that all 10 cards that might be used for a video poker hand are selected when you press the Deal button. Five cards are displayed. The remaining five cards are used in one of two ways. One way is to keep them in a stack and cards are dealt from the stack to replace discards. This is called "serial draw." "Parallel draw" is the other method, the one you described. The extra five cards are assigned positions, essentially being placed underneath the cards displayed, and used only if you discard the card dealt in that position. - Mitchell Tsai

Video Poker Mania was published in 1991 and things have changed since then. - Mitchell Tsai

Fast forward to the late 1990s. In a presentation at a day-long seminar for slot operators at the World Gaming Congress, James Maida of Gaming Labs International (GLI) described a group of RNG cheats in the midwest. One of the people in the group was the son of a slot distributor, so he had access to the game EPROM and disassembled the code to figure out the RNG algorithm. With the algorithm, he was able to write an RNG simulator program. - Mitchell Tsai

When a video poker machine selects all 10 cards at once, a cheat has all the time in the world until he presses the Draw button to figure out what the five replacement cards are. The cheats played a few hands and entered them into the RNG simulator program, which had the RNG algorithm and was able to determine where the RNG was in its cycle. Once the program knew that, they were able to enter the five cards they were dealt and have the program tell them the five cards that would be used to replace discards. - Mitchell Tsai

Because of this incident, Nevada changed its video poker regulations to require that machines select five cards on the draw, continue cycling the RNG, and then select replacement cards only after the Draw button is pressed. - Mitchell Tsai

The Standards for Gaming Devices document on GLI's site implies that they prefer that video poker machines select replacement cards only after the Draw button is pressed, but that it is not required. The method used depends on the regulations in your jurisdiction. - Mitchell Tsai