Ps/2 port on new motherboard?

[Hestafan]

So i realized when i was looking to uppgrade/ build a new computer to my self that a lot of the new motherboards had a PS/2 port and for me thats old tech. Is there a reason for the manufactors to take back te PS/2 port?

looking forward to your reply

[KarathKasun]

2 minutes ago, Hestafan said:

So i realized when i was looking to uppgrade/ build a new computer to my self that a lot of the new motherboards had a PS/2 port and for me thats old tech. Is there a reason for the manufactors to take back te PS/2 port?

looking forward to your reply

great for debugging stuff, and sometimes overclocking.  In some scenarios PS/2 ports work at temp ranges where USB becomes flakey.

[RollinLower]

To quote Reddit user BetterWatchOut:

Quote

PS/2 is good for N-key rollover, low latency, and the fact that it practically always works. If I have an issue with a USB keyboard that forces me to re-plug it in with each boot, I may not be able to reach the bios due to such an issue. This is becoming more of an issue as of late, as more keyboards are coming with built-in hardware that controls things like macros and backlighting that essentially makes it slower for booting. Backwards compatibility from USB to PS/2 doesn't hurt either, rather, giving PS/2 more reason to stay as a standard

 

[191x7]

A PS/2 port is a better choice for keyboards because it works on the base of interrupts - when you press a key it's executed immediately, there's no waiting for processor time (pooling rate) - that's better than regular USB keyboards which operate at 125 Hz (USB pooling rate) - and also most cheap USB keyboards have an NKRO of 3 while the same can have 6-NKRO when plugged to PS/2.

[Enderman]

6 minutes ago, RollinLower said:

To quote Reddit user BetterWatchOut:

 

There are USB keyboards with N key rollover, there are USB keyboards with lower latency, and there are USB keyboards that work without those certain issues the user is having.

 

PS2 is there because sometimes certain keyboards or mice will have issues operating before entering the OS, or if USB drivers are somehow malfunctioning.

 

None of that macro or lighting stuff makes booting slower.

The only thing is certain mine which require software on the computer to have those macros or lighting operate.

This does not slow down boot, it slows down your OS loading time.

Mice that store that stuff onboard don't have that issue, or mice that can operate without the software installed.

[Enderman]

4 minutes ago, 191x7 said:

A PS/2 port is a better choice for keyboards because it works on the base of interrupts - when you press a key it's executed immediately, there's no waiting for processor time (pooling rate) - that's better than regular USB keyboards which operate at 125 Hz (USB pooling rate) - and also most cheap USB keyboards have an NKRO of 3 while the same can have 6-NKRO when plugged to PS/2.

1) USB keyboards can have a polling rate (not pooling rate) of 1000Hz which is 1ms, faster than PS2. PS2 is not immediate.

 

2) N key rollover means that all keys can be pressed and register. If it has only 3-key rollover then it is not N key rollover.

 

3) Only cheap keyboards will have a limit to the rollover, any decent quality keyboard will have n key rollover.

[191x7]

Cheap (regular) USB keyboards do not have a polling rate of 1000. 

 

N Key Rollover - the N stands for a number - there's no keyboard with an "unlimited" KRO. PS/2 is 6-KRO. Cheap USB keyboards are 3 to 5 KRO. USB Gaming keyboards that advertise a higher KRO (some even advertising Antighosting and not mentioning KRO) usually have a 10, 20, 24 or 30 KRO.

 

Here's a Lenovo USB keyboard, holding both Shifts and typing the text A QUICK BROWN FOX JUMPS OVER THE LAZY DOG.:
A QUIK BROWN FO JUPS OER HE LA DOG.

Here's how the same looks on my G710+ (24-KRO which they advertise as N-KRO): A QUICK BROWN FOX JUMPS OVER THE LAZY DOG.

 

I'm at work and have no time to check if my spelling, grammar and translations are actually correct. Pooling, polling, potato, potato.

[manikyath]

49 minutes ago, 191x7 said:

A PS/2 port is a better choice for keyboards because it works on the base of interrupts

and yet.. if your cpu cant keep up, it's just gonna park that hardware interrupt for later processing anyways.

(been in that place before, actually..)

a hardware interrupt only means the cpu immediately responds and picks up the value from the keyboard, it doesnt mean that it'll actually do anything with said value until it seems fit to.

 

my guess is that it's brought back because the number of other ports is decreasing too (no more huge DVI/VGA blocks, decreasing number of USB ports, etc.) they have room for it, and just put it on so they can have an additional checkbox on the spec sheet.

[Enderman]

5 hours ago, 191x7 said:

Cheap (regular) USB keyboards do not have a polling rate of 1000. 

 

N Key Rollover - the N stands for a number - there's no keyboard with an "unlimited" KRO. PS/2 is 6-KRO. Cheap USB keyboards are 3 to 5 KRO. USB Gaming keyboards that advertise a higher KRO (some even advertising Antighosting and not mentioning KRO) usually have a 10, 20, 24 or 30 KRO.

 

Here's a Lenovo USB keyboard, holding both Shifts and typing the text A QUICK BROWN FOX JUMPS OVER THE LAZY DOG.:
A QUIK BROWN FO JUPS OER HE LA DOG.

Here's how the same looks on my G710+ (24-KRO which they advertise as N-KRO): A QUICK BROWN FOX JUMPS OVER THE LAZY DOG.

 

I'm at work and have no time to check if my spelling, grammar and translations are actually correct. Pooling, polling, potato, potato.

1) this is cheap and 1ms  https://www.amazon.com/Zalman-Unlimited-Multi-Key-Keyboard-ZM-K600S/dp/B0196J3IPE

 

2) https://en.wikipedia.org/wiki/Rollover_(key)

https://lifehacker.com/n-key-rollover-anti-ghosting-and-other-keyboard-featu-1643804346

X key rollover is where you replace X with a number.

N key rollover is where you replace N with the number of ALL keys on the keyboard.

[burnttoastnice]

21 hours ago, 191x7 said:

there's no keyboard with an "unlimited" KRO. PS/2 is 6-KRO. Cheap USB keyboards are 3 to 5 KRO. USB Gaming keyboards that advertise a higher KRO (some even advertising Antighosting and not mentioning KRO) usually have a 10, 20, 24 or 30 KRO.

 

Expensive keyboards exist with true N key rollover, some of which have each individual key wired in to the microcontroller individually, and others using the typical matrix arrangement. An example of such is the Happy Hacking Keyboard - which supports full rollover over PS/2, as long as there is BIOS support.

 

20 hours ago, manikyath said:

and yet.. if your cpu cant keep up, it's just gonna park that hardware interrupt for later processing anyways.

(been in that place before, actually..)

 

LOL the good old days of Windows XP... computer would completely lock up but still respond to mouse movement and keyboard activity . DOS is so guilty of 'buffering' interrupts though, for lack of a better word

[nick name]

There are lot of cheaper motherboards with old connectivity options for those poorer markets where old tech is still used daily. 

 

Edit:

 

I now realize this conversation is more focused on ps2 ports and not just older ports in general.  

[GeoSquigg]

I've been told that supposedly there's little to no latency due to it causing an interrupt. Modern non-budget keyboards offer low latency as well and you couldn't tell the difference with the human eye

 

I did run into a problem where I had turned fast boot on in the bios, which caused the system to boot before the USB devices were powered and had time to react so I couldn't get into the bios without clearing the CMOS. A ps2 keyboard may have been able to get me around that. I don't have one to test this tho.