Comment by wtallis

HP's early graphing calculators definitely had very high latency. But they dealt with it properly, which PC's don't. An HP-48 series calculator will buffer dozens of keypresses, and handle them in-order as if the UI had been instantly responsive. So you don't actually have to wait for a menu or dialog box to be drawn to the screen—if you've learned the necessary input sequence to perform the task you want, you can enter it at full speed. The keyboards were also very high quality with great tactile feedback, so you didn't need visual feedback on the screen to know your key press had been registered.