Getting 12864 LCD to show 2004 LCD information

I have the usual arduino/ ramps 1.4 setup together with full graphic LCD, this one: [reprap.me]
All works fine on my corexy printer up to 30mm/s printing speed but above that 8bit Arduino does not have enough processing power for both corexy movement calculations and information of full graphic lcd. Printer makes short pauses in-between movements. This seems like a well documented issue, especially on Delta printers.

Now the easiest solutions is to get a 2004 display or 32-bit board (which I might do later).
But is it possible to get a 12864 display to show 2004 display's information? This would save me from buying any new components.
I am using Marlin.

Edited 1 time(s). Last edit at 02/16/2016 02:44PM by Edvardas.

It doesnt work that way

The reason the graphic lcd bogs down the arduino is that it send every pixel to the display, so for lets say a 8x8 character (no idea what they are in reality) you have to send 8 bytes of data (plus any protocol overhead) per character

A 20x4 you just send the character you wish to display, 1 byte (plus any protocol overhead) per character (ignoring the few re programmable characters tricks)

so the glcd is 8 * the load (very approximately)

So sure you could make it look just like the 20x4 display, but it wouldn't help.

I see. I guess it might be possible to just use 20x4 pixels but dots are quite much more smaller on graphic LCD so a text would be really small and hardly readable.