beglebone-black and L3 interconnect


i’am using the GPMC of the beaglebone/beaglebone-black to communicate with a FPGA board. I struggle a bit to get the device tree configuration right to connect to the GPMC (and disable the eMMC), but i now have a stable communication. What bother me is that when switching from beaglebone with 3.2 kernel to beaglebone-black with 3.8 kernel the communication speed got divided by (at least) 3 with the same GPMC timings (and using EDMA) and this speed can vary very much over time (EDMA should guarantee stable speed). So i’am wondering what really changed with the beaglebone -black (or 3.8) kernel concerning the L3 interconnect ? How can i check the L3 frequency in command-line ?