Posted by Intensify on 19, 2001 at 9:25 AM:
In Reply to: Ron Michallick and Andrew Warne... posted by Bugfinder on 19, 2001 at 7:55 AM:
Bugfinder:
This is definitely a limitation of the keyboard (ps2 port). It is, technically, IMPOSSIBLE to push 3 buttons at **EXACTLY** the same time. It may be close (like milliseconds), but the keyboard encoder scans at a fixed rate picking up keypresses and sending them IN ORDER to the computer via the PS/2 Port.
On an arcade machine, however, the buttons are, more or less, wired DIRECTLY to the pcb (through some kind of connector). This allows you to literally register 3 button presses at EXACTLY the same time.
However, the chances that you actually pushed all 3 buttons in the arcade at *EXACTLY* the same time are slim to none, there had to be a delay, albeit VERY SMALL, between the presses. However, if a ps/2 keyboards scan rate is too slow, it would show that delay as much larger.
Now i've heard that USB Keyboards have a faster scan rate than ps/2 keyboard but am unsure if this is a limitation of the ps/2 port or just the keyboardds themselves.
I have an e-mail into Hagstrom Electronics (keyboard encoders) and am inquiring about the whole situation, and will let you know as soon as I get a response what they said.
--Intensify