Not the best of examples: 25 * 1024*1024 = 26214400 26222722 vs. 26214400 could well be in the noise for the time accuracy or how exact the clock rate is vs. nominal. (I'm not saying that you are wrong, just that the example is not clearly faster than a nominal 25 MB/s.)
True. But considering there's overhead, and if the clock really is set to 50 MHz (sc->sc.sc_clkbase = 50000), then this should be showing a number greater than the maximum possible at that clock rate. I don't have any faster cards than a Samsung EVO +.
John