Thanks God. Somebody who speaks English

@aorusaki

5 жыл бұрын

facts :D

@nahhhhhhhhhhhhhhhhhhh

2 жыл бұрын

So tru.

thank u .....keep up the good work doug

it's owesome, i finally figure it out.

If I'm not mistaken the carry ripple adder diagram has a mistake (the 3rd AND gate from the right is connected to the ci input, and a input twice, wheras is should be connected to the b input)

Dank

03:27 So what's the difference anyway? The second adder still needs to wait for the carry logic to generate it's carry, and in a normal ripple adder the carry is also "immediately available to the next adder" as soon as it has been calculated :P The problem lays in that calculation, though, which takes some time - more and more with each bit. It can look like a clever device which is supposed to be faster, but only because you don't see what's happening inside that box at the bottom. There still are logic gates, the more in number the more bits you process. It just extracted out the carry logic into that box, but the number of gates needed is still the same, and you still cannot get the next bit unless you get the carry from the previous bit. 04:40 Exactly. The rippling effect is still there. So what's the deal? :P Where the "speed" comes from, REALLY?

@DougShook

7 жыл бұрын

Well in the video I say that we'll take a look in class but since you weren't in my class you can try this for yourself: Sketch up a 4-bit adder in both styles, down to the gate level. The logic for the lookahead is given to you in the video. Assume each gate has 2ms of delay (a simplification, but it works). Run through the addition process in both adders and determine how long it will take. At a high level, the lookahead adder is faster because it sacrifices size (it has many more gates) for speed.

@aorusaki

5 жыл бұрын

@@DougShook hehehehehe

@aorusaki

5 жыл бұрын

@@DougShook good point

This video is misleading. Carry lookahead logic has to be instant, like in NesoAcademy's video. There should not be any ripple effect in this module like you suggest.

@duality4y

Жыл бұрын

its not the carry lookahead block generates the carry where needed it generates a c0 throught c3 where needed given that it could have been illustrated better for sure