EPROM
EPROM stands for Erasable Programmable Read Only Memory. It is a type of memory chip that retains its data, even when the power is switched off. It can be programmed through a special device, and some can be erased by exposure to strong ultraviolet light.
On the Z32
On the Z32's ECU, the EPROM contains information essential to the engine's operation. Fuel injector timing and pulse widths, ignition timing, speed limiter, rev limiter, and more information is all stored on the EPROM. Usually, when people talk about performance or upgraded "chips," what they're actually referring to is an ECU which has had the original EPROM desoldered (removed) and replaced with a socket, into which a new EPROM is installed. The new EPROM often contains a tune based on the factory EPROM, but modified slightly to improve throttle response, remove speed limiters, provide fuel maps for higher-flowing fuel injectors, etc.
Note: When installing a new EPROM, pay close attention to the orientation of the "notch" on one side of the EPROM. The socket itself should have a corresponding notch, and when inserted into the socket, the EPROM's notch should point towards the diagnostics selector. The ECU's motherboard also has a printed label under the EPROM or socket that shows the correct orientation of the notch.
