Speed of memory versus speed of CPU, Computer Engineering

Assignment Help:

In the past there was a large gap between speed of a memory andprocessor. So a subroutine execution for an instruction for illustration floating point addition may have to follow a lengthy instruction sequence. Question is; if we make it a machine instruction then just one instruction fetch will be needed and rest will be done with control unit sequence. So a 'higher level' instruction can be added to machines in an effort to improve performance.

Though this supposition is not very valid in present era where Main memory is supported with Cache technology. Cache memories have decreased the difference between memory and CPU speed and so an instruction execution by a subroutine step may not be that difficult.

Let's explain it with help of an illustration:

Suppose floating point operation ADD A, B needs the subsequent steps (presuming the machine doesn't have floating point registers) and registers being used for exponent are E1, E2, and EO (output); for mantissa M1, M2 and MO (output):

  • Load exponent of A in E1
  • Load mantissa of A in M1
  • Load exponent of B in E2
  • Load mantissa of B in M2
  • Compare E1 and E2

-  If E1 = E2 then MO ← M1 + M2 and EO ← E1

Normalise MO and adjust EO

  • Result will be contained in MO, E1

Else if E1< E2 then find the difference = E2 - E1

  • Shift Right M1, by difference
  • MO ← M1 + M2 and EO ← E2
  • Normalise MO and adjust EO
  • Result is contained in MO, EO

 Else E2 < E1, if so find the difference = E1 - E2

  • Shift Right M2 by difference above
  • MO ← M1 + M2 and EO ← E1
  • Normalise MO and adjust E1 into EO
  • Result is contained in MO, EO

 Store the above results in A

 Checks overflow underflow if any.

If all above steps are coded as one machine instruction then this simple instruction will need many instruction execution cycles. If this instruction is made as part of machine instruction set as: ADDF A,B (Add floating point numbers A and B and store results in A) then it would just be a single machine instruction. All above steps needed will then be coded with help of micro-operations in form of Control Unit Micro-Program. Soonly one instruction cycle (though a long one) may be required. This cycle will need only one instruction fetch. While in the program memory instructions will be fetched.

Though faster cache memory for data and Instruction stored in registers can create an almost similar instruction execution environment. Pipelining can further increase such speed. So creating an instruction as above may not result in faster execution.


Related Discussions:- Speed of memory versus speed of CPU

Importance of artificial intelligence, Businesses are interested in AI bec...

Businesses are interested in AI because of the characteristics it offers that no other systems type offers. That is AI ability to: a. Preserve Intelligence and Knowledge: C

What is organizational structure, What is Organizational Structure? A b...

What is Organizational Structure? A business organization may be structured in many dissimilar ways, depending upon the environment within which it handles.  There is always

Ann representation - artificial intelligence, A NN Representation ANNs...

A NN Representation ANNs are skilled on AI lessons because of their inspiration from brain studies and the truth that they are applied in an AI jobs, namely machine learning.

Memory that can be used in a 16-bit computer, What is the maximum size of t...

What is the maximum size of the memory that can be used in a 16-bit computer and 32 bit computer? The maximum size of the memory that can be used in a 16-bit computer is 2 memo

What is check box, A dialog box, generally square, that records an on or of...

A dialog box, generally square, that records an on or off value.

Calculate grade of service in a particular excahange, In a particular excha...

In a particular exchange during busy hour 1200 calls were offered to a group of trunks, during this time 6 calls were lost. The average call duration being 3 minutes Calculate

Prolog programming language, Prolog Programming Language : Probably pr...

Prolog Programming Language : Probably programming languages are procedural: than the programmer specifies exactly the right instructions (algorithms) required to get an agent

What is pointers function, Visual basic applications have very rich and fle...

Visual basic applications have very rich and flexible applications but there is single limitation when using pointer function. Windows API has limited support for function pointers

What are spa/gpa parameters (sap memory), What are SPA/GPA parameters (SAP ...

What are SPA/GPA parameters (SAP memory) SPA/GPA parameters are field values saved globally in memory.  There are two ways to use SPA/GPA parmeters: By setting field attrib

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