Datapath design problem?

[Shenli]

Hi all,

I am reading "Coding Guidelines for Datapath Synthesis" from Synopsys.

It says "The most important technique to improve the performance of a
datapath is to avoid expensive carry-propagations and to make use of
redundant representations instead (like carry-save or partial-product)
wherever possible."

1. Is there any article talk about what's "carry-propagation" and how
to avoid use it?
2. What's "redundant representations" mean?

Please recommend some readings about it, thanks in advance!

Best regards,
Davy

[Ray Andraka]

Post by Shenli
Hi all,
I am reading "Coding Guidelines for Datapath Synthesis" from Synopsys.
It says "The most important technique to improve the performance of a
datapath is to avoid expensive carry-propagations and to make use of
redundant representations instead (like carry-save or partial-product)
wherever possible."
1. Is there any article talk about what's "carry-propagation" and how
to avoid use it?
2. What's "redundant representations" mean?
Please recommend some readings about it, thanks in advance!
Best regards,
Davy

That really is targeted to ASIC implementations. The performance hit
for carry propagation in FPGAs that have a "fast carry chain" is
mitigated by the much faster carry propagation on these special
dedicated circuits. With that in mind, if you are designing on an FPGA
with fast carry logic, then this admonishment doesn't apply.

Redundant representations refer to alternative number system
representations that avoid the propagation of a carry signal across the
width of a data word as a result of arithmetic operations. They are
not,however, without their own hardships.