AD1955A without a cpu???

I am helping my kid build a Streamer out of an old Emotive Cd Player with a failed DVD drive. The Dac is a AD1955A and we are trying to make it work without the use of the onboard microprocessor. we found that the board has an unpopulated header for I2S. We cut the traces from the processor to the Dac chip For the I2S signal. And we are sending I2S MCLK, BCLK, WCLK SDAT from an old Rigisystems USBPAL board (to be replaced later). We have it working, but only at 44.1khz and 48khz. The usbpal and dac chip can go to 192khz. And we can see that the usbpal board is working fine. But we get no output above 48khz.

I found another post here in Diyaudio with one small mention that 48khz is the max without cpu support????

Can anyone expound upon this??? Is that fact and why? What does the cpu need to do to support higher sample rates??