Fetch Decode Execute Cycle in more detail
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- Опубліковано 5 чер 2024
- This computer science video illustrates the fetch decode execute cycle. The view of the CPU focusses on the role of various registers including the accumulator, memory address register, memory data register, current instruction register and the program counter. The arithmetic and logic unit and the control unit are also shown. For simplicity, the machine code commands being executed are represented by assembly language code.
NOTES:
To fetch an instruction from main memory into the CPU, the memory address of the instruction is copied from the program counter register into to the memory address register.
The instruction is then copied from the main memory into the memory data register.
The instruction in the memory data register is then copied into the current instruction register.
The fetch part of the cycle is now complete so 1 is added to the contents of the program counter (the program counter is incremented).
The program counter now contains the memory address of the next instruction to fetch, before the current instruction has been decoded.
The instruction in the current instruction register is then decoded by the control unit, and then it is executed.
If the current instruction is complete, the next instruction is fetched, decoded and executed in the same way.
Some instructions require data to be fetched from the memory in order to be completed, such as the instruction ADD 11. To fetch a data item from the memory, the main memory address of the data item is copied into to the memory address register (the memory address is part of the instruction, in this example it is 11).
The data item is then copied from the main memory into the memory data register.
The data item in the memory data register is then copied into the arithmetic and logic unit.
Some instructions require data in the accumulator register to be saved in the main memory, such as the instruction STORE 12. To store a data item into the main memory, the memory address is copied into to the memory address register (the memory address is part of the instruction, in this example it is 12).
The data item is then copied from the accumulator register into the memory data register.
The data item in the memory data register is then copied into the main memory.
Notice that when anything is copied FROM the main memory (instruction or data item), its memory address is first put into the memory address register, and it is then copied into the memory data register.
Notice that when anything is copied TO the main memory (data item), its memory address is first put into the memory address register, and it is then copied into the memory data register first.
Whole 2 stupid semesters and things get clear as water from this 8 min. video. I dont know why i even go to college.
I feel you braw,What a worthless place to go for years.
you tube wont give you a paper called diploma, which sometimes is requiered ;)
Tell me about it....i have just grasped this whole thing now after 5 semesters.
TC royce I KNOW RIGHT. this video really help me a lot
TC royce you can say that again
Why can't our teachers teach like this, I have always had problems with this concept since my O'levels and this guy just clarifies it like some 3rd Grade concept in an 8 minuite video.
Hats off ❤️
You're very welcome, and thank you :)KD
@@ComputerScienceLessons You have no idea how grateful I am for this. I have been struggling for ages and ages now around the concept of this cycle and how it works. This video was so clear, I understood it so much better than almost anything on the internet. Thank you so much. Keep up the good work!
what grade did you get then?
watching it 14 hours before my computer science exam helps a lot 👍
Excellent explanation; far easier to understand than the OCR textbook. Thank you!
OMG THIS VIDEO LITTERALLY SAVED ME I LEARNED MORE IN 8 MINUTES THAN HALF A SEMESTER
Me too
The only best explanation of fetch decode and execute cycle, I wish I could thank you in person.
An excellent explanation. It is worth a good lecture in education. Thanks everyone very much who made this short video available to public
You are welcome. :)KD
I have been involved in C programming for so long, I thought I would refresh my memory on this! Thank you and God bless!
You're most welcome :)KD
Never really understood this until I found this video, thanks a lot man
Exam is in a hour, good luck guys
I'm just gonna put this on repeat for 3 hours now then I'm good, thx doc
I suggest you draw a sequence of diagrams from it. Good luck :)KD
This video is top class of all internet content, because it can be understood by non-native English speaker. There are other videos full of knowledge too, but often I can't really catch on the go what the guys are even pronouncing, let alone understanding computing. Thanks for your work!
this is definitely by far, the best explanation on this subject that I've seem to date, i've whatched several other videos, but could never understood completely, thank god I found this video, you just gained on more subscriber. from brazil.
The clearest video about this on youtube!You deserve great credit ! Thank you !
Thank you sir, this truly helped! I was unclear of the difference between PC and MDR, but you explained brilliantly.
Awesome stuff man, comprehensive and quick.
appreciate it
Comprehensive and detailed. Good job Kevin!
I didn't understand my textbook but I utterly understand what you explained in the video.
Sincere thanks.
Ok this makes sense i finally get this. What a useful 8 min video unlike the whole 1 hour lesson at school
Thank you Kevin, i used your explanation in my presentation and the teacher gave me full mark.
Thank you.
1 Hour looking for something helpful and taken into understanding, and this video saves it all.
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You are a life saver. I was confused and now I will have time to watch Star Wars A Solo Story tonight or tomorrow.
This explanation is PURE GOLD. It's excellent! Thank you!!!
Thank you for the lovely comment :)KD
Ooh wow a 7 mins vid helped me understand faster than the many many classes that my technology teacher have given us 🐸✋
Delighted to help :)KD
@@ComputerScienceLessons You deserve way more recognitions sir. Is there anyway we can thank you? Because you really helped me in Computer Science revisions with those videos.
You are a Great Teacher.
Thank You
I finally start to understand what is going on under the hood ..
Thank You
You are very welcome indeed. Thanks for the lovely comment. :)KD
A. M. A. Z. I. N. G. video. Someone finally makes sense with a clear example
Thank you. You are most welcome :)KD
THANK YOU SO MUCH THIS IS A LIFE SAVER IVE BEEN SEARCHING FOR DAYS!
Thank you. Exactly what i needed to grasp the concept.
good one...now I'm clear
It's working then
NORMAL ENGLISH THANK YOUUU!!!
True!
Thank you very much for this video!
He's British.
@@frankanonymous3766 no he is bri'ish
@@dmm2708 ahahahahahahahahahahahhahhahahhhh
Your channel is so underrated I've learned way more things thank u
Glad to help. Thanks for commenting :)KD
Thank you so much for this video. I am building a CPU for my architecture course but I was a little lost on the exact order of procedures. This helped me immensely.
Glad to be of help. If you are building a CPU (something I would like to do one day), you might find Ben Eater's site useful. eater.net/8bit/
Amazing! Truly amazing. Super clear, logically explained and well explained.
Thank you :)KD
Simply put, great video. Recommend watching it.
Dude, what a tutorial! Thank you so much for helping me, right now I understand it 100%. It's explained so simply.
you are most welcome :)KD
This is awesome!! Thank you for the quality content!!
I don't understand why things get (or at least look) more complicated and un-understandable in university.. why do they always try to introduce stuff in a complicated manner?
Thank you so much for the explanation!
Thank you so much for a very clear explanation of Fetch and Execute Cycle.
You are most welcome. Thanks for the comment. :) KD
Just amazing! Thanks a lot!
No words to appreciate .....You have done fantastic work , it will help a lot..
Delighted to be of service. Thanks for the lovely comment :)KD
just perfect, saved hours of searching.. thanks!
This is by far the best explanation ive seen yet
Kind of you to say so. Thanks. :)KD
No one can explain it better than ben eater in his 8 bit computer series :)
I love Ben Eater. I built his 8 bit computer for a wall display. :)KD
straight to the point. love it!
Wow, this set things crystal clear in my head.
Glad to help. :)KD
Great video. Really helping me through me this summer class.
Thanks Kevin, that was a big help. I searched through an endless pile of garbage on the internet to get here. Will subscribe. Looking for more.
Thank you for the video. Great explanation
Thank you so much for making this content available!
You are most welcome :)KD
These explanations are so good, thank you so much
Thank you, for this great explanation. which made me understood the whole semester doubt in few minutes .
You are very welcome :)KD
Sir believe me it helped me a lot. You are so great that I think Thank You! word won't reach your greatness level. Superb!!!!!!!!!!
Thank you. Nice explanation.👏
Brother, your explanation is amazing. Thank you so much.
You are most welcome :)KD
Thank you for this! It was very clear.
One of the best Tutor ever seen. Excellent explanation
Thanks for the feedback :)
This is a really helpful video! Thank you very much!
I am really grateful for this video! Thank you!
You're welcome :)KD
thank you very much. this helped me a lot for my studies on Architecture. yes it is an excellent explanation!
thank you so much, i understood this better than the textbook given to me and my lecture, i think he even made a couple of mistakes like calling the Accumulator a fancy word for ALU, now ive learned the accumulator is just a register inside the ALU
this tutorial save me From reading 1000 of textbooks pages .... Thanks again professor .
bro i have no words.....you are real life hero, thx a lot😍😍
Thank you :)KD
Thanks I was searching for rtl and found this, it really helped me to understand rtl.
Thanks for the feedback. I'm glad it's helped.
Seriously this is a really good explanation thank u so much
Very good explaining we need more ppl like u
Best explanation ever. Very clear
Thank you so much im about to come up to my mocks and i couldnt get my head around this until now thank you.
You're most welcome :)KD
My Teacher taught us this but I had doubts and now I don't. Thank you so much!!
You are most welcome :)KD
Excellence teaching .....very important to computer science students .....
But u tried ur level best .....nice Job good job .
....this types of videos required to students ...my sir also stopped teaching and sending this video to prepare
😜
Extremely good explanation. Thanks.
You're very welcome :)KD
absolutely brilliant and detailed explanation. extremely helpful
Thank you, and you are most welcome :)KD
Great explanation. Very clear. Thank you very much. Greetings from Argentina!
Thank you. And thanks for saying hello :)KD
Very good explanation! Thanks.
thank you so much this was a life saver
the best explanation ever
Best video for priliminary students to understand the flow
Thank you Sir. It's explained really well.
Thank you :)KD
Visual explanation and your's description notes are also excellent sir👏
You're most welcome :)KD
Very clear and helpful, thank you
THANK YOU!!!!!!! Exactly what I was looking for!
:)
Great top-down summary (first time view on this channel, thx to G for the suggestion.). I'm curious to learn the steps EE folks took to take Von Neumann's idea that code and data are equivalent, and then implement a fetch decode execute cycle.
Glad you liked it. You might find it interesting to investigate John Von Neuman who I think was seriously underrated He played a big part in the development of quantum mechanics. :)KD
Amazing video very well explained! 👏👍
Thank you so much for this video!
You are most welcome :)KD
thank you sooo much ..... ur the best ........ easiest explanation , very simple i loved it
thanks for the good explanation. its clear now.
love the explanation!! thank you
Thank you. Excellent explanation.
Thank you :)KD
excellent explanation sir,thank you.
This video helped me a lot thank you!
You're welcome. :) KD
Thank you for the video sir.
still valid in 2021 :) , thanks a lot man
Indeed! :)KD
its awesome video sir.......respect you sir
Very Nicely Explained.. Thanks!
thank you so much, clear simple explanation :)
You're most welcome :)KD
Great explanation! Very clear and easy to follow. Thank you so much!
Fantastic video, you're a legend
Excellent job of explaining
He explained it soo simply!! 👌
:) :) :)
thank you so much sir. this really help me a lot
Great explanation!
nice explanation thank you very much
thanks so much this was very useful as i am doing my as level. My exam is a new one so i don't have text book yet as they haven't released it yet.