I don't know either when it did what, but when Amigas got faster CPUs IIRC there were patches (or newer Kickstarts?) to move the decoding to the CPU because the

I don't know either when it did what, but when Amigas got faster CPUs IIRC there were patches (or newer Kickstarts?) to move the decoding to the CPU because the blitter was slower than the CPU then.