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Unformatted text preview: ls. An EPROM can be reprogrammed on the order of 1,000 times. An electrically-erasable PROM (EEPROM) is akin to an EPROM, but it has an internal structure that allows it to be reprogrammed electrically. Unlike EPROMs, EEPROMs do not require a physically separate programming device, and thus can be reprogrammed in-place on printed circuit cards. An EEPROM can be reprogrammed on the order of ½¼ times. Flash memory is a family of small nonvolatile memory cards, based on EEPROMs, that can be plugged in and out of a desktop machine, handheld device, or video game console. Programs stored in ROM devices are often referred to as ﬁrmware. When a computer system is powered up, it runs ﬁrmware stored in a ROM. Some systems provide a small set of primitive input and output functions in ﬁrmware, for example, a PC’s BIOS (basic input/output system) routines. Complicated devices such as graphics cards and disk drives also rely on ﬁrmware to translate I/O (input/output) requests from the CPU. Accessing Main Memory
Data ﬂows back and forth between the processor and the DRAM main memory over shared...
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