Topic 4 subtopic 2 : Memory allocation, data alignment and register

Memory Allocation

Memory allocation is the act of reserving a chunk of memory for some set of data.Memory contains bytes.Some of those bytes are instructions ,and some of those bytes are data.MIPS processors typically divide memory into three parts:

• Text segment
• Data segment
• Stack segment

Data Alignment
Its value and the storage location(address).The address of a data can be evenly divisible by 1,2,4, or 8.In other words,data object can have 1 byte,2 byte,4 byte,8 byte alignment.

MIPS Data Sizes

Register

The MIPS microprocessor contains 32 user accessible registers that are numbered as 0-31.

• Register are 32 bits for MIPS.
• Register $1,$26,$27,$29 are reserved for special purpose by the assembler,compiler and operating system.
• Register $0 is hard wired to the value zero , and $31 is the link register for jump and link instructions but can be used with other instructions with caution.

The following table summarizes the usage convention for these registers:-

*** Coprocessor 0 contains exception control registers that handles exception.
SPIM doesn't implement all of the coprocessor 0's registers , since they are not much useful in a simulator or part of the memory system , which is not implemented. However, it does provide trap registers as show as below.

Trap Register: 

Exception code register:

LIM ZHEW SHENG
B031210379