[Discuss OpenCPI] Changing SDP external port BRAM usage

James Kulp jek at parera.com
Tue Sep 10 16:51:31 EDT 2019

Yes, the default is 64KB per stream, and it is parameterized for this 
and other purposes.
The intention was to apply parameters to the "connection" element in the 
container XML which would determine this buffer size per off-chip stream.
Unfortunately that link in the code generator for containers (which 
generates the code that instances those modules) is not implemented.

The best I can suggest is to simply change the constant (64k) in 
projects/core/specs/sdp-properties.xml, which would of course apply to 
all streams.

The proper fix in the code generator would be harder.

I have filed the issue for the next release.


On 9/10/19 4:34 PM, Travis Murphy via discuss wrote:
> Each external port costs 16 RAM36E1 resources at default. Our design uses multiple
>   ports to handle separate data streams but the size of the buffers is overkill for
>   the throughput we need. We would like to reduce down the BRAM usage to reclaim
>   some resources. I was wondering if there is any way to individually set the memory_bytes
>   parameter in the sdp_send and sdp_recv devices that get generated on external ports?
> Thank you,
> Travis Murphy
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