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P4080DS Srio performance issue

Question asked by Andre Westerholz on Aug 30, 2017



I´ve a performance problem writing to a SRIO (1x  lane) device using outbound window with NWRITE.

When I write to the outbound window all data transmitted correct to the device but  the speed is very slow.


A loop writing 200 32 Bit values (800 Byte) to the outbound window takes about 46 µs.


uint32_t *OutboundAddr =...;

for(i = 0; i < 200; i++)
*OutboundAddr = 123;


SRIO is configured to have 2.5 GBit so I would expect a time ~3.2 µs


The other direction (device to Inbound window) works much better. Here transmission time is very near to the theoretical value. 


Currently I don´t understand why the the NWRITE to the outbound window is so slow.


Best regards