8-bit Carry Lookahead Adder
- 4 ticks
- 6175
- 13×19×25
Verified specs
Credits
- Builder
properinglish- Built
- February 14, 2013
- Uploaded by
embizone
File
- Name
8_bit_Carry_Lookahead_Adder.schem- Uploaded
- October 15, 2026
- Downloads
- 0
- Conventions
- followed
Inputs and outputs
| Input | Bits | Min SS | Power | Delay |
|---|---|---|---|---|
| A | 8 | 5 | hard | t = 0 |
| B | 8 | 5 | hard | 0t |
| carry in | 1 | — | hard | 0t |
| Output | Bits | Min SS | First change | Settles |
| 8 | 5 | 2t | 4t | |
| bit 0 | 7 | 2t | 4t | |
| bit 1 | 5 | 3t | 4t | |
| bit 2 | 7 | 3t | 4t | |
| bit 3 | 5 | 3t | 4t | |
| bit 4 | 8 | 3t | 4t | |
| bit 5 | 5 | 3t | 4t | |
| bit 6 | 7 | 3t | 4t | |
| bit 7 | 5 | 3t | 4t | |
| carry out | 1 | — | 4t | 4t |
Block distribution
- Solid
- 732
- Dust
- 662
- Transparent
- 88
- Torch
- 76
- Lever
- 17
- Comparator
- 16
- Repeater
- 8
Description
"Proper looka-head adder"
One of the first solid state 4 tick adders.
https://www.youtube.com/watch?v=MCDbADY7WxE
Timing
- Synced
- ✗
- Bits apart, output
- 290,448 changes
- Changes tested
- 915,456
Glitch: output, all off → A=1, B=1, carry in=0
| t | 0 | 1 | 2 | 3 | 4 | expect |
|---|---|---|---|---|---|---|
| output | 0 | 0 | 0 | 1 | 2 | 2 |
output, bit by bit
| Bit | First changes | Settles by | Glitches |
|---|---|---|---|
| 0 | 2 | 4 | 98,304 |
| 1 | 3 | 4 | 98,304 |
| 2 | 3 | 4 | 114,688 |
| 3 | 3 | 4 | 122,880 |
| 4 | 3 | 4 | 126,976 |
| 5 | 3 | 4 | 129,024 |
| 6 | 3 | 4 | 130,048 |
| 7 | 3 | 4 | 130,560 |