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Percom AT88-S1PD - 3.5"drive install? SD-X read FAT12?

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Why are "written" cells zero instead of one?

I believe it saved an extra transistor per bit cell. With EPROMs, you're basically charging a small floating capacitor acting as the gate of a FET. With no charge present (erased cell), the FET conducts and this is represented by a 1. Once the gate is charged, the FET no longer conducts. UV light can excite the electrons enough that they tunnel through the barrier and discharge the gate (and, they'll discharge themselves naturally over the next 20-50 years).

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