 Since boost converters are inherently more efficient than charge pumps, researchers developing low-power SSDs have proposed returning to the dual Vcc/Vpp supply voltages used on all early flash chips, driving the high Vpp voltage for all flash chips in an SSD with a single shared external boost converter.In spacecraft and other high-radiation environments, the on-chip charge pump is the first part of the flash chip to fail, although flash memories will continue to work in read-only mode at much higher radiation levels.In NOR flash, each cell has one end connected directly to ground, and the other end connected directly to a bit line.