Some of the common rules of assembly level language are as follows:
★ In assembly language the label field can be either empty or may specify a symbolic address.
★ Instruction fields can specify pseudo or machine instructions.
★ Comment fields can be left empty or can be commented with.
★ Up to 4 characters are only allowed in the case of symbolic addresses.
★ The symbolic addresses field are terminated by a comma whereas the comment field begins with a forward slash.
The main components of the Ven Nuemann architecture were as follows:
★ It consisted of a main memory which would be used to store all the data and instructions.
★ It would consist of an arithmetic logical unit also known as the ALU. This part was to be able to work with binary data.
★ It also comprised of a control unit which would be responsible for the interpretation of instructions and their execution.
★ The control unit would also be controlled by the control unit itself.
Any program residing in the memory contains a set of instruction that need to be executed by the computer in a sequential manner. This cycle for every instruction is known as the instruction cycle . The cycle consists of the following steps:
★ Fetch instruction:
Like the name stated in this process the cpu fetches the instruction from the memory. The PC get loaded with the address of the instruction.
The instruction: In this process the instruction gets decoded by the processor.
★ In case the instruction has an indirect address the effective address is read from the memory.
★ Fetch the operand from the memory
Once the instruction gets decoded the processor executes the instruction.
Store the result in the appropriate place.
RISC meaning reduced instruction set as the acronym say aims to reduce the execution times of instructions by simplifying the instructions. The major characteristics of RISC are as follows:
★ Compared to normal instructions they have a lower number of instructions.
★ The addressing modes in case of RISC is also lower.
★ All the operations that are required to be performed take place within the CPU.
★ All instruction are executed in a single cycle hence have a faster execution time.
★ in this architecture the processors have a large number of registers and a much more efficient instruction pipeline.
★ Also the instruction formats are of fixed length and can be easily decoded.
The following are the main reasons for pipe line conflicts in the processor:
★ When the same resource is accessed at the same time by two different segments it results in resource conflicts. The only way to resolve this problem is to use separate data memories.
★ In case an instruction's execution depends on the result of a previous instruction and that result is unavailable it leads to data dependency conflicts.
★ Instructions that change the count of the PC can cause a lot of problems. This is prevalent particularly in the case of Branch instructions. A method to resolve this issue is known as delayed load where certain instruction are made to execute in a delayed manner to avoid conflicts.
An instruction can be considered to be a command that has been issued to a computer to perform a particular operation. The instruction format contains various field in them such as:
★ Operation Code Field:
Also known as the op code field, this field is used to specify the operation to be performed for the instruction.
★ Address Field:
This field as its name specifies is used to designate the various addresses such as register address and memory address.
★ Mode field:
This field specifies as to how effective address is derives or how an operand is to perform.
★ For ex. ADD R0, R1. In this case the ADD is the operand whereas the R1, ans R0 are the address fields.
The micro-operations in computers are classified into the following categories:
★ Register transfer micro-operations:
These type of micro operations are used to transfer from one register to another binary information.
★ Arithmetic micro-operations:
These micro-operations are used to perform on numeric data stored in the registers some arithmetic operations.
★ Logic micro-operations:
These micro operations are used to perform bit style operations / manipulations on non numeric data.
★ Shift micro operations:
As their name suggests they are used to perform shift operations in data store in registers.
Considered to be the simplest this method involves the updating of the main memory corresponding to every write operation. With this the cache memory is also updated in parallel in case it also contains the word specified at the address. The primary advantage of this method is data integrity, the primary and the cache memory both contain the same data.
In this method only the location in the cache is updated. Whenever such an update occurs a flag is set which makes sure that in case the word is removed from the cache the correct copy is saved to the main memory. This approach is usually taken when a word is constantly updated at frequent intervals.
This form of mapping is a modified form of the direct mapping where the disadvantage of direct mapping is removed. Set-associative mapping allows that each word that is present in the cache can have two or more words in the main memory for the same index address.