Ultraboost

"Ultra-Overclocked Monkeys gain a small but permanent boost every time they are overclocked."

- In-game description

 is the 5th upgrade on Path 2 for the Engineer Monkey in Bloons TD 6. It replaces the Overclock ability with the Ultraboost ability. This ability now adds a 6.67% permanent "Ultra Charge" attack speed boost to the ultraboosted tower after the ability is applied to the tower (reduces attack cooldown by 4%). This special attack speed bonus can stack additively up to 10 times, and grant ~66.6% attack speed to the target monkey when maximized (40% attack cooldown reduction). The permanent boost and the overclock boosting are different bonuses, meaning that they are not calculated together. Cooldown for the ability is 35 seconds, 10 seconds less compared to its predecessor, and initial cooldown is reduced to just 5 seconds instead of 15.

When an Ultraboost is applied to the Monkey Village, the Monkey Village instead gains a 2.5% range buff per Ultra Charge, up to 25% permanent range increase. For Banana Farms, they will produce +66% more bananas per round, with +6.67% more bananas per Ultra Charge (up to +66% increased production).

Alongside the new ability, the Engineer's nailgun now has 30 pierce instead of 15 from Overclock.

It costs $102,000 on Easy and $120,000 on Medium, $129,600 on Hard, $144,000 on Impoppable.

Description
Ultraboost equips the Engineer Monkey with a high-tech visor and an electricity-powered resource generator on his back. Similar to Overclock, the nailgun is actually a technologically advanced gun connected to his carryable generator. The Engineer no longer wears a pencil on his ear, but instead wears ear protection that comes from his high-tech visor. The monkey also wears shoes.

Ultraboost ability
The Ultraboost's Overclock ability and a normal Overclock ability cannot stack despite being depicted in the tower buffs when selecting the tower. The visual effect is the ability applied later.

Besides an additional Ultra Charge provided from the Ultraboost (plus additional extra range for Monkey Villages), similar rules regarding the Ultraboost's Overclock ability are shared with Overclock:
 * Overclocked monkeys gain ~66.6% attack speed (40% attack cooldown reduction).
 * Overclocked Monkey Villages gain 25% range during the Overclock boost.
 * Overclocked monkeys last depending on tier of the tower:
 * Tier 0 towers or Level 1-3 Heroes will be Overclocked for 105 seconds. (300% uptime)
 * Tier 1 towers or Level 4-7 Heroes will be Overclocked for 90 seconds. (257% uptime)
 * Tier 2 towers or Level 8-11 Heroes will be Overclocked for 75 seconds. (214% uptime)
 * Tier 3 towers or Level 12-15 Heroes will be Overclocked for 60 seconds. (171% uptime)
 * Tier 4 towers or Level 16-19 Heroes will be Overclocked for 45 seconds. (129% uptime)
 * Tier 5 towers or Level 20 Heroes will be Overclocked for 30 seconds. (86% uptime)
 * Banana Farms increase income production by 66% during the round if Overclocked, regardless of cost of the Banana Farm being Overclocked, as their attack speeds are essentially the rate at which they produce bananas.
 * Cooldown of 35 seconds upon usage, rather than 45 seconds.

Summary
Ultraboost is the most expensive buffing tower in the entire game, excluding Support Sacrifice Temples. It is a greatly improved version of Overclock that adds small permanent attack speed boosts to the selected tower every time the ability is activated onto said tower. In itself, it is pretty weak, but its greatest value comes from maximum stacking for the long-term, most benefiting in the epic late-game (Rounds 101+) when applied to the strongest DPS towers, with particular benefit for Sun Temples and True Sun Gods.

Tips

 * As its cost is extremely high for just one support upgrade, it is better to use Ultraboost for late-game. Particularly, it is very useful on Sun Temples and True Sun Gods.
 * Other useful Ultraboost candidates include: M.A.D, Ray of Doom, Flying Fortress, Super Mines, Banana Central, and in very specific situations, Perma-Spike (for ranked bosses).
 * One Ultra Charge on a Monkey Village or a Banana Farm grants the effect of a tenth of an Overclock. The maximum 10x Ultra Charges is roughly the same as a normal Overclock on those towers. These effects are then also stackable with an Overclock effect; e.g. a farm with maximized Ultra Charge and an active Overclock will generate 4x more income per round than usual.
 * However, it seems that 10x Ultra Charge will actually grant 1 extra banana/crate drop on a farm from its already-boosted income.
 * As with Overclock, Ultraboosting a Monkeyopolis will not increase income production, but will increase its range.
 * The best crosspath for Ultraboost is not to crosspath it, unless it's for excelling mid-game. In that case, 0-5-2 is superior. Sentries from this tower deal greater damage thanks to Deconstruction, but this wastes potential for optimizing the nailgun's generous 30 pierce. Otherwise it's simply a waste of money to crosspath this tower.
 * The Ultra Charge will be applied when the tower is temporarily boosted and will persist when the temporary boost has expired.
 * Adding Energizer will decrease Ultraboost's cooldown to 28 seconds, allowing it to keep one Tier 5 tower overclocked indefinitely with full uptime.

Sounds
When deploying Cleansing Foam:
 * [foam bubbling]
 * [foam bubbling]
 * [foam bubbling]
 * [foam bubbling]

When activating Ultraboost Ability:
 * [Engine starting]

Trivia

 * Ultraboost is the fourth most expensive (non-Paragon) upgrade in the game, behind Super Mines, Legend of the Night, and True Sun God.
 * Since the addition of Paragons in 27.0, all Paragons so far outprice Ultraboost.
 * Flying Fortress used to be tied with Ultraboost as the fourth most expensive upgrade in the game, but this is no longer the case as of Version 22.0's price buff to the former.
 * Ultraboost is the most expensive upgrade to be purchasable on CHIMPS Mode before Round 100. This feat was first achieved by a user who was attempting this on Logs CHIMPS. The same challenge was attempted by Flying Fortress by other players, but failed due to extra costs.
 * The first recorded instance of Ultraboost purchased in CHIMPS was done on September 23rd 2019.
 * In 18.0, the addition of Admiral Brickell allowed Flying Fortress to be barely afforded in CHIMPS. The 18.1 nerf made it much harder to afford a Flying Fortress, but it remains still possible.
 * Until Version 16.0, Ultraboost could be linked to a Tech Bot but not for Overclock. For both Ultraboost and the later Overclock, applying Tech Bot onto either will automatically reuse its ability on the previously targeted tower.
 * Similar to Overclock, Version 14.0's official patch notes has an error regarding the Ultraboost attack speed boost nerf. The nerfed attack speed boost was actually from +100% to +66% instead of to +80%, and the Ultra Charges are decreased from +10% to +6.66%; this mistake is likely due to a confusion between the concepts of attack cooldown (i.e. for the multiplicative increase/decrease for an attack per unit time) and attack speed (i.e. for the percentage increase/decrease for the numbers of attacks per second).