Read Only Memory (ROM)· Permanent storage · Micro-programming · Library subroutines · Systems programs (BIOS) · Function table 44. Explain the necessity of implementation of EPROM (EEROM, Flash Memory). Read “mostly” · Erasable Programmable (EPROM) § Erased by UV (all the storage) · Electrically Erasable (EEPROM) § Takes much longer to write than read · Flash memory (intermediate between EPROM and EEPROM) Erase memory electrically 46) What is the main purpose of Cache Memory implementation? Cache memory is intended to give memory speed approaching that of the fastest memories available, and at the same time provide this fast memory the price of less expensive types of semiconductor memories. Small amount of fast memory Sits between normal main memory and CPU (off-chip cache) May be located on CPU chip or module (on-chip cache) Describe principles of Cache Memory work. Write Policy Must not overwrite a cache block unless main memory is up to date Multiple CPUs may have individual caches I/O may address main memory directly Write through All writes go to main memory as well as cache Multiple CPUs can monitor main memory traffic to keep local (to CPU) cache up to date Lots of traffic Slows down writes
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