by Bret » Fri Nov 20, 2015 4:17 am
Glad I could help.
In English, the key between PrintScreen/SysReq and Pause/Break is the Scroll Lock key. It's rarely used for anything practical, though I have seen it used in some spreadsheet programs. When Scroll Lock is enabled (it's a BIOS setting), instead of moving to the next cell up or down in the spreadsheet it moves the whole spreadsheet up or down on the screen. I also use the Scroll Lock status in one of my experimental/unreleased programs as well, one called KEYS2JOY which allows you to use the keyboard like a joystick (if you don't have a real joystick for a program that requires a joystick).
Some BIOSes insert really long delays when you press the ScrollLock, CapsLock, and/or NumLock keys. You might also want to see if you get the same delay when you press the CapsLock or NumLock keys, since I suspect they may have the same issue. One thing you can try is to use my SCANCODE program to intercept the ScrollLock key and turn it into some other key that doesn't cause a delay, or have it do nothing at all.
It's possible that SCANCODE will not really work all that well on a real-time system, but you could try it and see.
EDIT:
I also just thought of this. The delay could also be associated with the ScrollLock LED status light on the keyboard. I know sometimes it takes the keyboard a LONG time to process the LED request, but I have also seen BIOSes that purposely insert long software delays (I have no idea why they do it, I just know they do sometimes). Whether it's the BIOS or the keyboard hardware causing the problem, effectively disabling the ScrollLock key with SCANCODE should help, I think.