Editing Flash memory (section)

====Firmware storage====
With the increasing speed of modern CPUs, parallel flash devices are often much slower than the memory bus of the computer they are connected to. Conversely, modern [[Static RAM|SRAM]] offers access times below 10&nbsp;[[nanosecond|ns]], while [[DDR2 SDRAM]] offers access times below 20&nbsp;ns. Because of this, it is often desirable to [[shadow RAM|shadow]] code stored in flash into RAM; that is, the code is copied from flash into RAM before execution, so that the CPU may access it at full speed. Device [[firmware]] may be stored in a serial flash chip, and then copied into SDRAM or SRAM when the device is powered-up.<ref>Many serial flash devices implement a ''bulk read'' mode and incorporate an internal address counter, so that it is trivial to configure them to transfer their entire contents to RAM on power-up. When clocked at 50&nbsp;MHz, for example, a serial flash could transfer a 64 [[Mbit]] firmware image in less than two seconds.</ref> Using an external serial flash device rather than on-chip flash removes the need for significant process compromise (a manufacturing process that is good for high-speed logic is generally not good for flash and vice versa). Once it is decided to read the firmware in as one big block it is common to add compression to allow a smaller flash chip to be used. Since 2005, many devices use serial NOR flash to deprecate parallel NOR flash for firmware storage. Typical applications for serial NOR flash include storing firmware for [[hard drive]]s, [[BIOS]], [[Option ROM]] of [[expansion card]]s, [[DSL modem]]s, etc.