Overload glitch (Halo 3)

For the Halo 2 Overload Glitches, see here.

The overload glitch is a bug present in Halo 3. When too many objects are present in a map, the map becomes "overloaded", resulting in the deletion of the "oldest" objects. The glitch can be set up in Forge, and can be performed in Custom Games or Forge. One Campaign level is also prone to the bug.

Overloading a map is usually done to disable certain map features that prevent players from leaving a level's boundaries. Such features include the Brute Landmines on Sandtrap and the watchtowers on Sandbox.

Walkthrough

Multiplayer

Start a Forge session.
Enter Edit Mode, and place a Trip Mine. Alternatively, you may find one that has already been placed.
Set Trip Mines to Instant Respawn.
Return to Player Mode, and stand on top of the Trip Mine's spawn point. You should pick it up.
Throw the Trip Mine. You should immediately pick up another.
Continue throwing Trip Mines as fast as you can.

Eventually, the Trip Mines will explode on their own; this is because a Trip Mine will automatically detonate after 90 seconds. After this explosion, the map should be overloaded. Sometimes, however, the trick must be repeated in order to have a noticeable or useful effect. (In such cases, the Trip Mines usually reappear after the first explosion.)

In some cases, the Trip Mines may start to disappear in a blue flash. If this occurs, then the map is overloaded.

Note that you can drop Trip Mines faster by obtaining a second weapon and repeatedly pressing X and Y -- two X presses for each Y. (X + X + Y + ...) Note also that this fast method can increase the game's RAM usage, possibly leading to a crash.

The trick can be performed with other equipment items, like the Deployable Cover; however, other items take longer to overload the map.

Campaign

Currently, only The Covenant can be overloaded, by using two exploits. The first causes a large amount of Marines to spawn; the second, which requires Co-op, allows players to accumulate Hornets in the level.

During the first Hornet battle, when the Master Chief flies to Tower 3, both players should fly to the island in front of Tower 2. They should dismount their Hornets, such that the vehicles fall into the sea, but the players land safely on the island. A Marine should quickly fly another Hornet to the island.

At this point, one player (Person A) should fly the Hornet away, while the other (Person B) remains on the island. Person A should land the Hornet at a location that Person B cannot reach. Person A should then die; they will respawn with Person B. A Marine will bring a new Hornet to the island; the two players should repeat the process.

Eventually, the accumulation of Marines and unreachable Hornets will overload the map. If a player uses a Hornet to proceed to the next loading point, the other player will be transported forward, and all the Marines and Hornets will be removed from memory, ending the overloading effect.

Saving an overloaded map

Start a Forge session. In an out-of-the-way area that players can't reach (preferably outside the map), make a big pile of weapons and equipment. Once a large amount of items has been placed, spawn a scenery item on top of the pile. If it disappears, then place a bunch of movable scenery on it. Otherwise, keep trying.

When enough scenery has vanished, start a new round. If enough items have been placed, the map will be overloaded, and will be overloaded the next time it is loaded.

Some more specific instructions:

Spawn a good 50 to 80 weapons in one place.
Place a movable scenery piece on top.
If the scenery disappears, proceed to spawn additional cheap movable scenery.
After a good 50 spawns, set the scenery to Instant Respawn.
The game should pause for a moment.
At the point of the glitch, often one will experience lag, as well as the symptoms that are characteristic of an overloaded map.
Proceed to delete the spawned weapon pile; it is no longer needed. Save and exit.
Start up your map again. The movable scenery will immediately spawn and disappear in one place, causing a brief moment of lag. The map should then be overloaded. If the lag continues, revisit forge and undo the Instant Respawn trick for some scenery items. If necessary, delete some items.

Effects

Overloading tends to disable the "built-in" special features present on several maps. Sandtrap's Elephants will vanish. Lifts, such as the air lift on Blackout, will stop functioning. Epitaph's floating platform will fall. Most notably, the The Guardians' scripted appearances (on Sandtrap, Sandbox, and Snowbound) will stop functioning.

However, overloading a map may cause the game to use a lot of memory due to the excessive objects that need to be kept track of. The game's stability can decrease; lag is a likely result due to the increased CPU and GPU power needed to process and render the environment. The game may also crash in the worst cases.

Specific Effects by Level

Assembly: The air lifts stop functioning. The rushing air is still visible on the blue lift, but not the yellow ones.
Avalanche: Overloading the map multiple times will disable the man cannons. Overloading the map once at the area under the Spartan Laser cave will also work.
Blackout: The air lift stops working, though the rushing air is still visible.
Citadel: The invisible walls in the room under Rocket Launcher spawn will disappear.
Construct: The lifts no longer work. All weapons will be temporarily de-spawned.
Epitaph: The floating platform will fall and become movable. The shield doors and lifts will vanish. Most holograms will vanish.
Guardian: The main lifts are disabled, and the hologram no longer works.
High Ground: The main gate disappears, as do the movable gates near the Surface-to-Air Missile Launcher. The hatch on the bunker disappears.
Isolation: The lifts are visible but don't function.
Last Resort: The breakable bridge (that can be used to enter the spinning wheel) disappears.
Narrows: The built-in Man Cannons are disabled. All objects disappear for a few moments, then respawn. The rocket launcher on the lower level energy bridge disappears.
Sandbox: The watchtowers are disabled. The grid and the sky bubble's "floor" disappear, causing any movable objects in the sky bubble to fall.
Sandtrap: The Brute Landmines become inactive for the rest of the round. The lifts no longer work, though the air can still be seen. The Elephants disappear.
Snowbound: The built-in shield doors are cut, and the automated turrets no longer shoot.
The Pit: All major weapons (such as the Energy Sword) will disappear temporarily. The fan lifts stop functioning, although the air is still visible.
Valhalla: The built-in Man Cannons are disabled. All weapons and vehicles disappear for a few moments, then respawn.

Trivia

Some players have reported seeing Ghosts of Halo on maps after overloading them.
It should be noted that overloading will not disable the Guardians. It will, however, disable the various level features whose kills are credited to the Guardians.
It is also possible that the Guardians have a built-in script letting them stabilize any overloading map, as such saving it from crashing.