Read 1 : ARM Dev guide (About memory)

• The cache is placed between main memory and core. A cache provide an overall increase in the performance but with a loss of predictable execution time

• What is s memory width ?

The memory width is the number of bits the memory returns on each access - typically 8,16,32 or 64 bits. The memory width has a direct effort on the overall performance and cost ratio.

• Type of memory are being used
• ROM : Read only memory. to hold date which require no update or correction.
• Flash ROM : Can be written to as well as red, but it is slow to write so you should not use it for holding dynamic data. Its main use is for holding the device firmware or storing longterm data.
• Dynamic RAM : Most commonly use RAM for devices, lowest cost per MB, it need to have its storage all refreshed and given a new electronic charge every few mili-second, so need DRAM controller before using members.
• Synchronous Dynamic RAM : Runs on higher clock speed than conventional memory. It sync itself with processor because it is clocked.