 This often increases the speed of image write operations by several times, at the cost of losing the simple sequential read/write semantics of normal memory.Additional bits which are provided on some computer architectures, such as AMD64, allow the shadowing of ROM contents in system memory (shadow ROM), and the configuration of memory-mapped I/O.In early x86 architecture systems, especially where the cache was provided by separate chips outside of the CPU package, this function was controlled by the chipset itself and configured through BIOS settings.