Forum Discussion
Honored ContributorCyclone V speed is much slower
Hello. I am new to Cyclone V. I took my design for Cyclone III and recompiled it with Quartus II web 13.1. From the timing analyzer, I can see that the maximum clock rate is only 84 Mhz while I was getting 131 Mhz with cyclone III at the same C8N speed grade. The timing recommendation is incomprehensible. Would anyone who knows cyclone V well tell me if this is expected? Is Cyclone V significantly slower than Cyclone III? This doesn't make sense.
Thanks a lot. Jixiang34 Replies
Altera_ForumMove to a later version of Quartus (15.0)
The timing models were not final in Quartus 13.1 for Cyclone V and were very conservative (overly so). You should see much improved timing performance in Quartus 15.0. Pete- Altera_Forum
Thanks Pete. I have done just that. The speed does improved to 88 Mhz. However, it's still significantly slower than Cyclone III or Cyclone IV which I get comparable performance.https://www.alteraforum.com/forum/attachment.php?attachmentid=10792
- Altera_Forum
Ok that sounds wrong. I expect a significant increase in performance for Cyclone V from Cyclone III. My guess is there are some false paths that are getting ignored in the conversion, (IE the PLL Changed, so the old SDF file isn't valid anymore).
I would look at that. If you can send a timing report for both the designs we can look at it. Pete - Altera_Forum
Cyclone V is of much newer technology as compare to the Cyclone III. Thus, we should expect generation V to have much better performance than Cyclone III. As mentioned by anakha, I believe we might need to further look into the timing constraints to see if there is any anomaly.
- Altera_Forum
That's a good news because I do plan to move all to Cyclone V and the performance is important.
I do not seem to find a way to generate a timing report file. I opened the timeQuest analyzer and I see that I can write a SDC file but that isn't a timing report, is it? Thanks in advance. Jixiang - Altera_Forum
I did find a report file .sta.rpt. Is this what I should send you for both devices? Would you give me an email address?
Thanks in advance Jixiang - Altera_Forum
It does sound like some timing specs are missed. Have some paths for different names? 88 MHz is very slow and points to poor quality design.
- Altera_Forum
You are perhaps right but this is a new issue just to Cyclone V. I have done just fine with Cyclone 1-4.
- Altera_Forum
You have to replace pll ip, delete and recreate it then see if there are pll related warnings
- Altera_Forum
I have just done that. It make no difference. The max freq is still 88mhz.
