You can bump up bandwidth all day, but the stock timings were designed around "Complete Stability". With 1797Mhz we achieve 230GB/s error free. That's not bad at all for Polaris 4GB, plus your packing a Polaris 10 480 Core with some ROP's and TMU's disabled is all. I was able to pull 1,953Mhz on the 4GB modules with loads of errors but near the fastest around. Increase voltage didn't help and adjusting timings didn't help. It prefers no more than 1797Mhz ram and 100% stable at stock timings and stock voltage.
Focusing on the Core is what matters. Increasing the Giga Flop Output near much faster GPU's. It's rated like 5.8GFlops, I had the 480 up to 6.75GFlops on stock 65288 voltage. That's 16.38% more Giga Flops total throughput. The memory speed didn't help that number. The Core Clock helps that number and the ability of the core to maintain as high of clocks as possible. Which is why the BIOS I sent is only Step #1 for more performance. The first BIOS isn't the fastest, it's the 10th BIOS that's the fastest and most stable. Fiddling with the states so when it has to throttle which it must, it only goes down a little so maintaining high performance.
If set 1,438Mhz core that's solid but must throttle to stay within 75C Limits to my defined 1433Mhz... Then if needed 1416Mhz... Again if needed 1400Mhz... 1366Mhz.. 1333Mhz.. and so on... Stay well up there on it's big end maintaining way faster than stock performance all on stock voltage values. Meaning 65284, 65285, 65286, 65287, 65288.