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Altera_Forum
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10 years ago

Cyclone 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...
Altera_Forum's avatar
Altera_Forum
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10 years ago

Ok looking at the timing report, the paths in question are from CLK100 to RAMCLK.

Can you describe how these are related? Are they both 100 MHz from the the PLL?

Anyway It appears the "Default" mode of the Altera_PLL is now Direct mode instead of source synchronous or zero delay buffer. This is probably the root of the issue. Page 3 of the PLL doc talks about this:

https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/ug/altera_pll.pdf

I would play with the Operation Mode on your PLL and I'm sure you will find a setting that will zero out that delay.

Pete