geekhack
geekhack Community => Keyboards => Topic started by: Hyde on Fri, 02 November 2012, 21:02:21
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Just today I switch my plug from PS2 to USB because I find the PS2 plug is wobbly and USB has that nice "click" to it and it locks in place nicer. That and I haven't run into anything where I need NKRO yet.
Though what I notice is that I find my repeat rate is faster in PS2 compare to USB. I have set my repeat rate to shortest delay and fastest repeat rate in windows setting.
So now is it me dreaming or does it actually repeat faster?
I know PS2 is interrupt based and USB is polling based, and I'm guessing Filco poll at 125 Hz by default?
But I didn't have anything to measure it so it could be my perception is off or maybe PS2 is a tiny bit faster :confused:
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On USB repeat is entirely the OS you are running. You press a key and hold it the OS receives: Key-X <down> and decides whatever it wants to in regard to what to do about it for as long as it takes until it receives: Key-X <up>.
It's a bit simplified but that's the gist of it.
On PS/2 the keyboard actually has some say in things as does BIOS settings in regard to the controller talking to the KB.
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Ahhhhh, so it could potentially be true that PS2 is faster?
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Sure, PS/2 has a specific set of fixed speeds that you can switch it to. What your OS does with USB isn't really standardized like that.
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You're not crazy. I discovered it while moving zoomed photos around and while playing first-person shooters. PS/2 is faster and snappier. I just tested it out in Wordpad while timing and oh yeah it's quicker.
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As mentioned above, USB repeat rates are determined by the OS and are likely configurable.
Any perceivable difference in response time is likely attributable to the time it takes your keyboard to scan across columns looking for depressed keys, rather than the connector/protocol.
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I know PS2 is interrupt based and USB is polling based, and I'm guessing Filco poll at 125 Hz by default?
But I didn't have anything to measure it so it could be my perception is off or maybe PS2 is a tiny bit faster :confused:
PS/2 is faster than default Filco 1 according to this video (http://www.youtube.com/watch?v=BDeRtIsYP1Q). Filco 2 seems to have a 1000Hz polling rate (https://www.diatec.co.jp/en/det.php?prod_c=806), but it is possible to change USB polling rate so Filco 1 could be 1000Hz.
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It is a low speed USB device, so no 1000hz on Windows (without using unsigned drivers). We had the discussion on PS2 vs USB here (http://geekhack.org/index.php?topic=30466.msg579124#msg579124).
Repeat rate means nothing in game. If the engine doesn't suck or really old, it would read raw inputs anyway. So there is a difference of 7ms between PS2 and USB low speed connection, which is well below the threshold of human perception. Then you need to add in the built in latency on debounce time, which you would get on either connection type. If you want faster repeat rate for general usage, then just change it in the keyboard options. Of course, if someone still think faster repeat rate matters. Throw all your keyboards away and buy a Zowie. They can do REALLY fast PS2 repeat rates.
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Forgive an Old Curmudgeon a moment of "Old Guy" glee, but I love it when the old stuff is STILL BETTER than the Fancy New Cheap Stuff they make today!!!
Like my IBM PS/2 Trackpoint M13 Black I use at work....... Everyone looks at you as if you are a little strange - why your own keyboard? It's SOOO Big! It's SOOO Loud! Why can't you be like everybody else..... TPF
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lol I do agree there are a lot of old stuff that are totally better made than the new stuff these days. Oh and I switched back to PS2, it is indeed noticeably faster :)