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-   -   USB vs PS/2 Keyboard: latency, bandwidth -> inputs per second? (https://www.overclock.net/forum/373-keyboards/835911-usb-vs-ps-2-keyboard-latency-bandwidth-inputs-per-second.html)

dan_k 10-01-2010 07:17 AM


1.) PS/2 port, Wikipedia says, works at 10-16 kHz and I think protocol defines 11 bits per packet. That comes down to 16,000 / 11 = 1454.55 keys per second. True?

2.) USB default Windows polling rate is 125Hz, i.e. it has 8ms latency or lag between each packet. Now, even though each packet is 8 bytes long it seems USB keyboards still need to communicate only one key per packet, and that comes down to 125 keys per second. True?

While that may sound enough, it is only about 2 keys per frame @60fps animation, so if you play some fighter where you need to perform "DOWN+RIGHT+PUNCH" in a single frame this can be a problem, especially if there are two players both trying to report their combos in the same time.

USB keyboards are so much worse than PS/2?

ripster 10-01-2010 09:00 AM

Get a Razer Mechanical.

1000Hz polling rate.


The gold connector makes it go faster too.

Arkuatic 10-01-2010 09:12 AM

Originally Posted by ripster View Post
Get a Razer Mechanical.

1000Hz polling rate.


The gold connector makes it go faster too.

ripster 10-01-2010 10:46 AM

jk. I was taught using the Socratic method.

Wikipedia is not the best place for researching PS/2. Try this. And don't forget the difference between packet based protocols and IRQ old fashioned 1987 era protocols like the Gameport, Serial Port, and Parallel Port.

Good times. I'll miss that good old PS/2 port too.

ripster 10-03-2010 09:17 AM

The OP posted the same thing over at Gamedev.net.

Didn't end well.
Except that the number you have just called rubbish is from the specification, which you asked about in your original post.

I'm issuing you with a warning for intentionally being argumentative and goading other members.

Guys: In this sort of situation, just report the thread and don't get into a degenerative flameware.

Thread closed.
The key thing to remember is USB is a packet based protocol with the HID specification able to handle 10 keys per packet. The maximum keystrokes per second is 500. 500. One second. Try it, doubledogdareya.

It's good to know this stuff because if you believe the Razer Marketing department y'all should be using a Black Widow at 1000hz.

sefwe 10-03-2010 10:08 AM

Ah a typical gangbang thread. A new guy is asking for something, and the gang is telling him he doesnt need it. Backing it up with solid evidence like

I have strong belief that if you take bunch of "pro" CS:S and Quake players, put them on a server where the ping is seemingly 100, when in reality it is 40, they will feel that they perform sub-par.

... Most of this is psychological.
This doesnt change a fact that i somehow believe that an USB keyboard could be a bottleneck here. Besides, im not quite sure what is it you expect to hear. Just get a PS/2 keyboard, its better anyway. Problem solved.

PS. A Serial Port will most likely outlive USB. (as RS232 )

ripster 10-03-2010 10:30 AM

USB is the number one technological innovation of all time.

Is RS232 the one with lots and lots of those little pointy things? They would sometimes bend and break off. Like PS/2.

sefwe 10-03-2010 10:49 AM

This article is both outrageous and unfunny.

I wonder why it lists USB at all, with it being a latercome competitor to FireWire and all Difficult to count it as an innovation, other than maybe in Bill Gates' mind. Then again, with 2 videogames in the top10 of all PC tech innovations in the history of mankind im not surprised.

ripster 10-03-2010 11:00 AM

Doom! Another classic from the days of RS232, Apple ADB, Parallel, Firewire, Gameports.

And PS/2.

88EVGAFTW 10-03-2010 11:06 AM

Just get a good mouse that lets you adjust polling rate and a ps2 keyboard

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