The Overclocker Upgrade is used to speed up IndustrialCraft Machines at the cost of higher energy consumption. In order to use it, place it in one of the four slots on the top-right of any machine which is able to be upgraded.
Each upgrade reduces the operating time to 70% of the previous value and increases energy consumption by 60%. The overclocker upgrade's effects stack exponentially. For example, two upgrades makes the machine operate at (0.7)^2 = 0.49 times normal time (100% faster) and use 1.6^2 = 2.56 times the energy (139% more). 8 of them will run the machine at over 8 times normal speed, and use over 43 times as much EU.
An overclocked machine's speed cannot exceed 1 operation per tick, so adding additional overclocker upgrades beyond that is pointless.
Maximum speed benefits can be achieved with 16 overclocker upgrades in Macerators, Compressors, and Extractors, 13 in Electric Furnaces, and 10 in Recyclers. In each case you're going to need to put in Transformer Upgrades, Energy Storage Upgrades, and use Glass Fibre Cables to keep up with the machine's power demand.
There is a glitch where if you have a stack of 16 overclocker upgrades and you repeatedly click it in the top left box, it will macerate/smelt with a very small use of power and complete the action almost instantly!
8 cables (6 copper + 12 rubber making 4 extra cables) or (3 copper + 6 rubber + 2 more cables you might have), along with an Extractor to produce the Coolant Cells.
The EMC cost is (4*256) + (6*85) + (12*24) = 1822, which is a little more than 28 Obsidian.