Minimum SPI frequency

Is there a recommended minimum SPI frequency to support the W6100 on a 100Mbit network?

I’d like to use MACRAW but it seems even if the Host MCU ran the SPI clock at 70Mhz (max) we will never keep up with 100Mb/s. Though it certainly depends on how busy the network is…

Is it ok to run the SPI bus at say 2 - 5 MHz and rely on the TCP windowing to slow down the remote device? If the Rx buffer remains full for a time does that mean no ARP or ICMP messages can be responded to?



As far as I know, the minimum guaranteed speed of the SCLK is 33.3 MHz which was tested and measured with the stable waveform.
I think it would be good to refer to the picture below regarding SPI speed.

If the RX buffer is full, wiznet chip can’t receive data.