Sega's 1988 arcade version of Tetris uses the exact same RNG seed every time it boots up, resulting in the infamous 'power-on pattern'.And because the computer it was included with, System/360 mainframe, is widely regarded as their greatest work and was the computer of The '60s and The '70s, the generator became so widespread that the traces of it periodically surface even now, over 50 years past.How bad is it? Aside from the fact that every number is odd (which is bad on its own, yet easy to work around), any three adjacently generated numbers can be mathematically related into a plane ◊ (which looks like 15 planes when plotted due to modulo arithmetic).

RANDU, the infamous random number generator included on IBM computers in the 60s.

Slot and keno machines nowadays prevent this by constantly advancing the seed even while it's not being played, by either incrementing the seed number or just rolling and throwing away the outcomes note and even this must be done very carefully, as some of the more popular ways of implementing it can actually make the problem worse due to 'RNG jitter'. This allowed one clever guy to win big three games in a row.

Another example was found in a keno machine that would always roll the same sequence of numbers after each reboot since it used the same seed every time it booted up.

Someone wrote a program that, using the programmer's knowledge of the RNG and the player's own pocket cards, could tell the player everyone else's cards as well as the future cards that would come off the deck, completely breaking the game.

For a specific example, at least one poker site was cracked this way.While many video games rely on PRNG, there are some that use this really badly: This is not Idiot Programming because computers can't do real RNG without an outside source. What they do instead is that they take a preset string of numbers as a 'seed' and use that to generate a stream of random-looking numbers. As mentioned on the front page, computers do not have pure RNG, but instead they use something called PRNG (pseudo-random number generator).

Red border on mdickie games