Eliminating data hazards - computer architecture, Computer Engineering

Assignment Help:

Eliminating data hazards:

Forwarding

NOTE: In the following instance, computed values are in bold, whereas Register numbers are not.

Forwarding involves adding output data into a previous stage of the pipeline. For example, let's assume we desire to write the value 3 to register 1, (which already contains a six), and then add 7 to register 1 and hold the result in register 2, for instance

Instruction 0: Register 1 = 6

Instruction 1: Register 1 = 3

Instruction 2: Register 2 = Register 1 + 7 = 10

Following execution, register 2 would contain the value 10. Though, if Instruction 1 (write 3 to register 1) does not fully exit the pipeline before Instruction 2 begins execution, it means that Register 1 does not contain the value 3 when Instruction 2 performs its addition operation. In such type of event, Instruction 2 adds 7 to the old value of register 1 (6), and so register 2 would contain 13 instead for example Instruction 0: Register 1 = 6

Instruction 1: Register 1 = 3

Instruction 2: Register 2 = Register 1 + 7 = 13

This error takes place because before Instruction 1 has committed/stored Instruction 2 reads1 Register the result of its write operation to Register 1. Thus when Instruction 2 is reading the contents of Register 1, register 1 still contains 6, not 3.

Forwarding (described below) helps right such errors by depending on the fact that the output of Instruction 1 (which is 3) may be utilized by subsequent instructions before the value 3 is committed to/stored in Register 1.

Forwarding is implemented by putting back the output of an instruction into the previous stage(s) of the pipeline as soon as the output of that instruction is available.  Forwarding applied to our instance means that we do not wait to commit/store the output of Instruction 1 in Register 1 (in this instance, the output is 3) before making that output accessible to the subsequent instruction (in this particular case, Instruction 2). The effect is that Instruction 2 uses the right (the more recent) value of Register

1: the commit/store was made instantly and not pipelined.

With forwarding enabled, the ID/EX[clarification needed] stage of the pipeline now has 2 inputs: the value read from the register mention (in this instance, the value 6 from Register 1), and the new value of Register 1 (in this instance, this value is 3) which is sent from the next stage (EX/MEM)[clarification needed]. Additional control logic is utilized to determine which input to use.

813_Eliminating data hazards.png


Related Discussions:- Eliminating data hazards - computer architecture

Is there a macro recording interface in gimp, Not at this time. With GIMP b...

Not at this time. With GIMP based on GEGL, so that all changes are non-destructive, it will be much easier to execute this feature by just remembering all nodes in given range and

Command line argument value, Make a console application to show different m...

Make a console application to show different messages depending on the command line argument value. Use Select-case statements.(same to switch block)

What can digital circuits do?, Circuits can be designed to implement a spec...

Circuits can be designed to implement a specifictaske.g. a simple circuit could compare two inputvoltages and give a high output if they matched anda low output if they did not mat

By which digits are represented, In a DTMF phone, digits are represented by...

In a DTMF phone, digits are represented by: (A)  Orthogonal frequencies. (B)  Orthogonal Phases. (C)  Orthogonal codes. (D)  Orthogonal pulses. Ans: Di

What is typical storage hierarchy, Q. What is typical storage hierarchy? ...

Q. What is typical storage hierarchy? A typical storage hierarchy is displayed in Figure above. Though Figure shows only block diagram however it includes storage hierarchy:

How will you allocate sub system, How will you allocate sub system? All...

How will you allocate sub system? Allocate every concurrent subsystem to hardware unit. General purpose processor or specialized functional unit as follows: Estimate per

What is capacitor-based keyboards, Q. What is Capacitor-Based Keyboards? ...

Q. What is Capacitor-Based Keyboards? These keyboards are based on the idea of Capacitance. A simple capacitor comprises a pair of conductive plates having opposite charges and

Explain disk cartridges, Q. Explain Disk Cartridges ? Disk Cartridges:...

Q. Explain Disk Cartridges ? Disk Cartridges: Removable disk cartridges are an option to hard disk units as a form of secondary storage. Cartridge generally comprises one or

Padovan string , A Padovan string P(n) for a natural number n is defined as...

A Padovan string P(n) for a natural number n is defined as: P(0) = ‘X’ P(1) = ‘Y’ P(2) = ‘Z’ P(n) = P(n-2) + P(n-3), n>2 where + denotes string concatenation. For a string of t

What is a convertor?, Converter is an application that converts distance me...

Converter is an application that converts distance measurements among metric and U.S units.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd