SR-56C? Interesting idea.

[pauln]

We are probably saying the same thing but just to make sure: in the TI-57, the processor speed is also constant but sometimes the display doesn't get updated/refreshed for a while and therefore it goes blank.

This can be illustrated by looking at the ROM activity monitor in https://www.pcjs.org/machines/ti/ti57/rev0/: when idle, the program counter (brighter green dot) is around address 0x04a7 (DISP instruction) constantly refreshing the display.

If one presses "88 sin", the program counter goes to larger addresses, where there is no DISP instructions, for a couple of seconds and the display goes blank.

The point is that there is no instruction in the TI-57 to tell the display to go blank. The display goes blank because it hasn't been updated/refreshed for a few milliseconds and therefore the light has faded away.