Jump to content
  • 1

Maximum power consumption on the Nexys Video


steckdenis

Question

Hi,

I successfully downloaded, implemented and run the Mandelbrot viewer of Hamster for the Nexys Video (https://github.com/hamsternz/FPGA_Mandelbrot). The only modification I had to do was to remove Genesys2-specific components instantiated in top_level and the input/output ports related to the PMods that I don't have. The modified design works perfectly well, Hamster's work is really amazing!

At the beginning of top_level, a couple of constants allow us to configure how the Mandelbrot generator is built. I wanted to play with these constant and implement 2 multipliers (per pipeline stage) as LUTs, instead of using DSP slices. The result is a design with tighter timing (but still routable, it seems that Vivado 2016.2 improved timing for this design), but less DSP slices used.

Another difference is that the design consumes more power. When running the power analysis on the original design (many DSP slices, not so many LUTs), 5W are reported. For the modified design (less DSP slices, more LUTs), 8W are reported.

I thought that this would not be a problem, as I have a fan that does a great job at cooling-down the FPGA (45 °C for the reference design, 65 °C without the fan), but the Nexys Video board "reboots" when I try to program it with the 8W design. Basically, I program the board over JTAG, I get the message that says that programming was successful, but the board de-programs itself and returns to the original Digilent design (HDMI passthrough with temps on the LCD). If I put my bitfile on an USB thumb drive, programming works as expected, but then the board fails to run the design and re-programs itself from the USB drive (creating a programming cycle).

I have seen that the voltage regulators used on the Nexys Video allow for a maximum of 8 amps on the 1V rail (FPGA core). Could this be the root of the problem? How much can the Artix 7 A200T consume if completely filled with a high-clock-rate design (like Hamster's)? Is there any way to still allow a large and complex design to run on the board?

For reference, I have uploaded my bitfile here (the forum does not allows 6MB files to be attached to threads). This is a raw binfile for use with the Digilent Adept tools.

Thanks!

Link to comment
Share on other sites

4 answers to this question

Recommended Posts

Hi steckdenis,

Great question! (although unfortunately I don't know the answer to it myself) I have asked some of our applications engineers about this and to potentially have them try it out for themselves; they will get back to you here on the Forum.

Thanks,
JColvin

Link to comment
Share on other sites

Hi Steckdenis,

I looked up the reference manual for the Nexys Video. According to the reference manual the 1V rail (FPGA core) can only draw 4amps. I think that since you are trying draw 8amps the board, it gets overloaded and because it can't draw the 8amps it wipes the program and then reboots itself.

https://reference.digilentinc.com/reference/programmable-logic/nexys-video/reference-manual

If you have any other questions feel free to ask.

lengland

 

Link to comment
Share on other sites

Hi lengland,

I've just seen that yesterday. The 1V rail is driven by an ADP5052 if I'm not mistaken, and I previously thought that it was configured to provide 1V at 8 amps (by running the first two output channels in parallel). However, you are right and only one output channel is used for 1V, giving 4W.

I'm a bit surprised as the Artix 7 200T can consume quite a bit more than that. Fortunately, this is not really a problem for me (my design is large but I can lower the clock speed to save power, I just need to test its behavior), but it may be for other people.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...