Are there any fast 256 bit decoders for Minecraft?

Solution 1:

Your problem is probably not the speed of and gates, they are usually just a few ticks. I'd rather guess that the problem is that you set them up in a way that the decoder is sending the signal to the and gates one after another, instead of all at the same time.

Your screenshot doesn't relly show much about the design you used, however there are a lot of decoders out there. (really just google a bit and you'll find tons)

I've built one for you that is instant on the rising edge (but takes inverted input):

This one uses 3 bits, but can be expanded if required. The torches you see in front take an extra tick, but may be required depending on your design. The input is 000 so the far right one is selected.

In this design, a redstone block with dust on it is used for a 0, a block with a torch is used for a 1. (from right to left: 000, 001, 010)

The pistons in the middle (or the odd ones) have an extra piston on top so they're updated by the redstone above:

Some more screenshots: