How can I tell the difference between display sleep vs. computer sleep on my MacBook Air (Late 2010)? How can I tell the difference between the entire computer sleeping and only the display sleeping?

I'm trying to diagnose sleep problems, and one of the basic things I need to know is the difference between these two kinds of sleep modes. I can't rely on the times I set in the settings since that is what I'm trying to debug.

I have a 13" Macbook Air late 2010, if that makes any difference.

Things I thought might help:


Trackpad move vs. trackpad click. I've noticed that when I force the computer to sleep via the Apple menu, it's not enough to move around the mouse via the trackpad... I must press down on the trackpad or another key.
Caps Lock light: If I leave caps lock on for testing purposes, sometimes I will see the light turn off, while other times it stays on. I thought that perhaps this could tell me the difference between the two.
The Apple logo on the back side of the laptop, although its light seems to go off in both cases, so that doesn't help
Plugging in a USB device which has a light, which indicates when the computer is supplying it power. The light seems to shut off when in sleep mode, but stays on when the display is sleeping. I'm not sure if this is a reliable method, though


The problem with the first two methods is that I was able to recreate a situation where the caps lock key remains on, but the trackpad mouse move does not wake the computer.

Are there any reliable ways to know if the entire computer has gone to sleep or not?
There's a really simple way to test this if you have another Mac, or any other machine really.

Turn on one of the Sharing features on the Mac in question (File Sharing, Remote Login etc.) and try to connect to it from something else. If the entire machine is asleep it won't work. If just the screen is asleep it will.

I assume you're connecting to some kind of wireless network with the MacBookAir, so you could also check the list of connected wireless clients on your router. If the entire machine is asleep it should not be connected. It may still show up in the list of DHCP clients (clients that have requested an address from the router recently), but it should not be connected.