EPROM
From Sega Retro
EPROM stands for Eraseable Programmable Read Only Memory. These chips are usually in a ceramic package with a small glass window that allows you to see the chip die. The purpose of this window is to allow erasure of the ROM by ultraviolet light so it may be reburned with other data such as a later build of a game to allow it to run on a normal host console rather than a development system.
--Payphone Ed 11:14, 9 Jan 2005 (MST)