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edwinleung
Newbie
Newbie
670 Views
Registered: ‎03-01-2020

Change Memory Device Interface Speed in Vivado for Alveo U250

Hi,

I would like to know is there a way to lower the DDR4 frequency from the default speed rating of 1200 to 800?

I tried to change the "Memory Device Interface Speed (ns)" setting in Vivado, but it seems fixed at 833.

Please help.

Thanks,

Edwin

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mcertosi
Xilinx Employee
Xilinx Employee
634 Views
Registered: ‎10-19-2015

Hi @edwinleung,

The DDR4 interface speeds are fixed for the acceleration flow. 

Are you using a Vitis platform for the u250 or doing something else? 

Regards,

M

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edwinleung
Newbie
Newbie
588 Views
Registered: ‎03-01-2020

No, I am not using the Vitis platform.  I have been using Vivado for top level Xilinx components instantiation and stitching, and using Vivado to constrain the design.

I don't have any experience using the Vitis platform, will I be able to change the DDR clock frequency if I use the Vitis platform?

Thanks.

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mcertosi
Xilinx Employee
Xilinx Employee
572 Views
Registered: ‎10-19-2015

Hi @edwinleung 

In the acceleration flow / platform usage you can change the kernel clock. There is automatic clock crossing logic that is then inserted from the user/kernel clock. 

If that clock crossing logic is handled for you, why would you want to decrease the frequency of the DDR4? 

Regards,

M

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edwinleung
Newbie
Newbie
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Registered: ‎03-01-2020

Hi M,

The reason why I want to lower the DDR clock frequency is that my FPGA tests tend to fail more if the ratio of the engine clock to the DDR clock is high.  I want my FPGA tests to fail more often which would help root cause the problem in my logic.  Cranking up the frequency of the engine clock results in lengthy P&R time, so I was hoping I can reduce the DDR clock frequency without changing the engine clock frequency.

 

I am confused, so you were saying it is possible to change the DDR clock frequency, either through Vivado or Vitis?

Thanks,

Edwin

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mcertosi
Xilinx Employee
Xilinx Employee
536 Views
Registered: ‎10-19-2015

Hi @edwinleung 

I see somewhat of what you are doing. This isn't standard and cannot be done in the standard flow. 

I apologize, it would likely be the best path forwards to replace and route to change your engine's operating frequency. 

Regards,

M

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