restricted Fmax

[Altera_Forum]

I should have some IO speed, something like 500Mhz, not toggling but pulses as short as 2ns. The logic is a few counters that could also be resynchronized. Wit a Cyclone3 I reach something like 250Mhz fo FMax. Even though I was planning to use the LVDS outputs, I wasn't yet able to assign them. Ok, then I tried an ArriaGX2, which should be much faster, but reached just 230MHz FMax. For FMax as well as restricted FMax. And also here, I'd like to use the LVDS outputs. I was able to assign Alt_Output, as Alt_Output_diff is not supported. 

ArriaGX2 is supposed to reach GBit speeds at the output. How is this done?  Edit : Fmax of my Cyclone3 is 160MHz, not 250.

[Altera_Forum]

Well i think the results you are getting are aligned to what it should be, although i have never worked with arria gx or cyclone so i cant comment on the 1Gb/s you are saying for the outputs but i really doubt that arria gx or cyclone can give such a baud rate. 

Anyways i am also attaching a snap shot from arria2 gx manual. Might give you a better view of the max frequency operations. Nevertheless even if your lc count is only 50 even then i think the results are reasonable . If you provide some insight on the resource counts and your sdc some experts here might help you.   GOOD LUCK

[Altera_Forum]

On second thought 1Gb/s you are talking about is the data rate while the operating frequency is around 300 to 350 Mhz max for ARRIA 2 GX. 

It can give that data rate ie 1Gbps , so i think your results are fine.

[Altera_Forum]

Thanks. Especially the Arria2GX is advertized as "Transceivers up to 16 at up to 6.375Gbps", so somehow the transceivers are there that are able to do this data rate.

[Altera_Forum]

Use the altlvds megafunction. The internal logic runs much slower, but is serialized before going out. (The transceivers can go much faster, but generally have more overhead for protocols. You don't have to use that overhead but altlvds should fit your needs)