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Visualizing ROMs 1: Diode Matrix ROM

To start with, ROMs come in a few different varieties. The most well known are EPROMs. These are ICs with a quartz window on the top, through which you can see the storage array on the silicon. This window is used to erase the ROM with ultraviolet(UV) light, then you can use a programmer to re-burn the ROM with other data. It remains mostly non-volatile, unless it’s erased with UV light again, via an eraser or by leaving it in the sun for a couple weeks. These kinds of ROMs are useful for when you need to reprogram the content, or if the production runs are relatively small. These are often used in video arcade machines, as the program or graphical data might need revisions, and production runs are not in the “millions”.”

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