TimeQuest Analyzer: "~DUPLICATE"

Altera_Forum · ‎01-23-2018

Hi there,

tl;dr: What does the postfix "~DUPLICATE" means in TimeQuest and why is it added?

I have some timing violations which I try to pin point via TimeQuest Analyzer. In the Path summaries of the problematic paths, I see a lot of i.e. "signalx", but also a lot of "signalx~DUPLICATE" (see also to real-life examples below). When I right click those nodes and view them in the RTL viewer (Locate Node -> Locate in RTL Viewer), they both "signalx" as "signalx~DUPLICATE" seem to refer to the same flipflop. In the RTL viewer I am also unable to locate the register "signalx~DUPLICATE". Does anybody know what this "~DUPLICATE" prefix means and why it is added to certain signals?

Cheers,

Wobbert


From: soc_system_final:u0|custom_fifo_final:fifo_57|writepointer~DUPLICATE
To: soc_system_final:u0|custom_fifo_final:fifo_57|readpointer~DUPLICATE

or


From: soc_system_final:u0|custom_fifo_final:fifo_57|writepointer~DUPLICATE
To: soc_system_final:u0|custom_fifo_final:fifo_57|readpointer

Altera_Forum · ‎01-23-2018

~duplicate is where it has duplicated a register, probably with a high fan-out, probably because it thought it was going to affect timing. There is a synth setting where you can set the maximum fan-out of a register. If it goes over this, it will create a duplicate to handle the extra fan-out.

Altera_Forum · ‎01-24-2018

Ah, makes sense now. Thanks a lot!