Old input lag testing methods


I’ve been trying to find the old threads regarding input lag and how people tested them (I recall markman did one, and there was an ST one with an LED comparing a port with an arcade board) I’ve been searching google and the forums for them and am unable to find them.

The reason why I ask is because I want to compare the input lag of two complete setups: a retron 5 with the ASUS 238h and nes/snes/genesis etc… with a CRT…

The simple solution in my mind would be get a camera, and splice an extension cable so it can plug into both consoles, but i’m worried about damaging my controller pcb. I assume i would only need to draw power from one console, so just leave the pin to the other console unconnected? are there any other concerns I haven’t considered? or technical knowledge that i’m clearly lacking/not considered from my desciription?

  1. Well the way controllers work you can’t just splice a cable and plug it into 2 consoles simultaneously.
  2. HDMI is going to lag compared to your CRT
  3. As the retron 5 is a emulator and there only so far emulators can go
  4. The NES and SNES controllers used a shift register as an encoder so its pretty fast. I forgot the method how a Sega Genesis controller works but is a expanded from how a Atari 2600 controller works. A Sega Genesis controller will work on a Atari 2600 console (you only get the d-pad and B button to work).


I am aware of all of that. I want to know how much more the lag is on the retron 5 setup. Any ideas how to get a simultaneous signal on both consoles? Again I recall something similar being done for ST and toodles doing something similar for MC Cthulhu (I said markman before but I meant toodles) they both have instructions on how they did it so people could replicate and verify their results. But I can’t seem to find those threads


Here is Toodle’s Lag input video.

As you are doing two separate systems with two separate displays You might want both displays the CRT and the HD being recorded by a high speed video camera.
You need 2 controllers with a input wired to the same button(s). You would also want 2 copies of what ever test game you are using. If you can you might also want in area being recorded is an indicator when the button is pressed. Maybe a LED.

Something maybe like this? Although you don’t need something this complex.


Oh, so they used two different controllers instead of just one. But yes, that was what I was looking for. Thank you. @Toodles Why a circuit to split the signal rather than just wiring a button to both boards? and the image shack links are dead =( Can you reupload the diagram somewhere please?


The ST test you’re thinking of is probably the one done by NKI.


For me it was convenient to hook the button line to the video signal, but that controls for the video set-up, which isn’t what you want here.


It’s very likely for the boards to interfere with each other in subtle ways, and possible for them to interfere with each other in unsubtle ways. Isolating them from each other controls for that.