Carry Lookahead Adders vs Tree adders for 32-bit addition

[abhinavt]

Hi guys,
I need fast 32-but adder units for increasing the speed of my design. When it comes to 32-bit addition, would Carry Lookahead Adders be better or any of the prefix/tree adders like Brent Kung adders?
Also, can anyone help me out with pipelined versions of any of these adders.

Thanks in advance,

A

 

[tariq786]

I think prefix adders are the fastest so far. Please check prefix adders on wikipedia. There is a good description of it available there.

 

[Ch. Harish Kumar]

I tried to know about prefix adders from google.. but i didn't understood how the carry is going to propagate to the next stage..
pls help me in that.

 

[ads_ee]

Doesn't anyone know how to perform a search?

**broken link removed**

I found this after looking on the wiki page for the prefix adders.

 

[jt_eaton]

What technology are you using?

Most of the work done in speeding up addition was done back when gate delay dominated the critical path and routing delay was not an issue. That is no longer the case for asic designers.

With todays newer technologies you put in a ripple carry adder and minimize the routing on the carry chain. You should find that any attempt to route the carry away from that array and back will cost more in routing time than it will save from replacing huge chunks of your carry chain.