Difference between register and memory

Answer 1

Registers are storage locations internal the the processor. CPU instructions operate on these values directly. On RISC processors, all data must be moved into a register before it can be operated. On CISC (Intel) chips, there are a few operations that can load data from RAM, process it, and save the result back out, but the fastest operations work directly with registers.

Also, there are registers that are set aside for certain tasks, these generally include a program counter, stack, and flags.

Each register also has a size that determines the maximum amount of data that can be processed at a time. The registers on Pentium chips, for example, are 32 bits.

Finally, there are generally only a few registers available on a processer. Intel chips, for example, have 6 general purpose registers, and several specialized registers including a base register, stack register, flags register, program counter, and some addressing registers.

Memory, or RAM, is located external to the CPU. Generally speaking, data has to be loaded into a CPU register from memory before the CPU can process it, RAM is much slower than registers, there is a lot more RAM than registers, and generally memory can be addressed on a byte boundaries, where registers may not be able to access all the bytes in a register.

To summarize: in general, registers are temporary storage in the CPU that holds the data the processor is currently working on, while RAM holds the program instructions and the data the program requires.

Hopefuly this helps,

--Eric Tolman

Answer 2

Registers are very small but are extremely fast - access time is usually 1 cycle.

RAM is a much larger and slower memory that applications use as a scratch space. RAM usually has an access time of about 100 processor cycles

Answer 3

1. You cannot take the address of a register variable.
2. Registers variables can be no larger than the word length of the machine.
3. Registers can be accessed much faster than main memory.
4. The machine cannot operate upon values in main memory, other than to move values to and from registers in order to operate upon them.

Answer 4

explain the each program memory addressing mode?