Why lcd controller is so important?

Pretty much so, yes. For starters, a CPU running off a single 16 MHz clock can't even generate a 10 MHz clock signal, much less output controllable data at that rate.

You don't necessarily need a specialized LCD controller, but you will need some device that the CPU can offload the LCD data refresh to. Either that, or a *much* faster CPU.

If you think of an LCD glass like a CRT, then can you display on a CRT without a controller ?

Yes you can, but it will require timing signals to be constantly driven but the microprocessor.

Same problem with LCD glass, someone has got to do it, its usually easer to do it with a controller.

good luck

don

Yes, most LCD panel accepts 1 bit or 4 bits data stream. But you need a big video buffer (16K to 32K Sram) and logic to serialize it at a constant rate.