[lowrisc-dev] Re: Question on lowrisc project

Wei Song ws327 at cam.ac.uk
Mon Feb 15 16:02:22 GMT 2016

Hello Pawan,

On 15/02/2016 15:54, Pawan Reddy Sibbala wrote:
> Hello Wei, 
> I have two questions that I'd like to ask you. 
> 1. The rocket core on the zedboard FPGA  currently runs at 25Hz. Could
> you tell me the maximum frequency at which it can run ? I was
> wondering if you already experimented with the parameters in
> "clocking.vh" to find the maximum frequency.

No, I did not. The maximal frequency is in between of 25 MHz and 50 MHz.
For the same configuration and the same FPGA, running at 50 MHz has some
timing violations.
The critical paths are in FPUs. So suppose if the FPU is disabled, it
may run at 50 MHz.
As running on FPGA is not the target and the design is not optimized for
FPGA, there should be space for speed optimization.
Even without any optimization, I believe it can easily run to 30 or 35
MHz, which I had not tried.

> 2. Does the new release of the untethered version of the rocketchip
> use a opensource IP for implementing the Memory Controller or does it
> use the Xilinx IP?

Those are Xilinx IPs.

> Thanks and regards,
> Pawan 

Best regards,

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