How are various portions of the CPU connected to perform an operation?

[rrrrr12345]

In CPU operation, after an instruction is fetched, when the opcode is alrithmetic, when it gets executed, various portions of the CPU are connected so they can perform the desired operation. For instance, an addition operation was requested, an arithmetic logic unit (ALU) will be connected to a set of inputs and a set of outputs

How is this connection being done physically?

R

 

[barath_87]

Re: CPU

The opcode is sent to instruction decoder (which is a demux) which sends the data to that particular block of logic that is to be performed in the ALU .... Say you want to perform addition then the adder block would be given with the data .... Pls correct me if I am wrong ...

 

[raghuram_msc]

Re: CPU

Hi all,

One step ahead of bharath... i would like to add that the entire effort is only to "locate" the precise block which would to the job. Finally the block referes to what i would call "Look-Up-Table" like our calculator and reroutes the "answer" to the requested location....!!!!

Hope me correct tooo....iam open for discussion..!!

Bye,
sai

 

[rrrrr12345]

Re: CPU

Hi all,
Finally the block referes to what i would call "Look-Up-Table" like our calculator and reroutes the "answer" to the requested location....!!!!

ya, I'm trying to find out how this "reroutes" being done physically? super huge multiplexor?

please continue to help me,
R

 

[tkbits]

Re: CPU

"Answers" are outputs.

Outputs are never routed, they are available everywhere they are connected. For interfacing with the outside world, outputs can be set to a high-impedance state, which is almost a disconnect.

Instead, inputs are selected (via multiplexing), and registers store input data by "capturing" them on a "clock" signal. Registers can have "enable" inputs that control whether the clocking will cause the register to update or not.

 

[ubna]

Re: CPU

The obivous answer is the control unit.
The cpu has various blocks like adder, multiplier,etc.
The control unit activates the required block needed by the data. The instruction conveys its requirement to the control unit by means of the opcode..