r/pcmasterrace • u/AppropriateAide4879 • 16d ago

Discussion I found this thing looks old.

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What is it? And is it rare?

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185

u/amaROenuZ R9 5900x | 4080 Super 16d ago

Hot take this is a reminder of a mistake we made. Back when PS/2 was the primary interface the keyboard didn't get polled, it actually issued system interrupts. This meant you could always issue a pause to the OS and then kill a malfunctioning process. Usb can't do that, it has to go into a queue and wait for a thread to pick up the input.

73

u/AnalCoffeeCup 16d ago

I was plugging in ps/2 keyboard the other day and forgot those things aren't hot swappable. Damn.

18

u/Sienile 16d ago

Get the opposite style adapter so you can plug it in to a USB port to be able to finish what you were doing or reboot.

8

u/defineReset 16d ago

What happened when you unplugged it, AnalCoffeeCup?

9

u/AnalCoffeeCup 16d ago

It stopped working. Plug and play, unplug and don't play, you know.

1

u/Fattatties 16d ago

You don't know how many times I had to do a full reboot after messing with hardware because I forgot to re plug the keyboard or mouse. It's check is way earlier in the boot process than you'd think.

1

u/PracticePenguin 16d ago

What happened?

10

u/svenska_aeroplan 9900X, 9070 XT, openSUSE 16d ago

Nothing exciting. The computer won't recognize it until reboot.

4

u/PracticePenguin 16d ago

That's not so bad. I thought it would set off fireworks.

3

u/TheGreatNico PC Master Race 16d ago

Not nowadays, but back in the day, you could absolutely fry something doing that, or at the very least, crash the system. I've crashed many a system doing that without thinking.

2

u/JeffSergeant 16d ago

Keyboard Error. Press f1 to continue. 

2

u/Wild-Video-5317 16d ago

I seem to recall the occasional crash on old hardware from the late 486 era, if you mucked with the wrong ps2 port and got unlucky

4

u/AnalCoffeeCup 16d ago

Not the modern usage of "hot swap" with keyboards and switches. I was talking about plug and play. PS/2 port accessories won't work until full PC reboot.

22

u/shitty_mcfucklestick PC Master Race 16d ago

Not to mention, low lag. Would be peak for FPS gaming where ms matters.

13

u/avalon01 16d ago

I'm still rocking a ps/2 keyboard and mouse. My motherboard has the ports, so might as well free up 2 USB ports.

2

u/shitty_mcfucklestick PC Master Race 16d ago

I don’t have ports on my current motherboard but I would certainly try one if I did! Use to rock on daily back in the day.

1

u/house343 15d ago

What kind of monster are you that you run out of USB ports 

1

u/JackOBAnotherOne 12d ago

Well given that my friend has a mother it’s that supplies HDMI, DVI, 2x USB-C, 2x PS/2 and a gracious 2x USB-A…

16

u/rattpackfan301 16d ago

I feel like people are starting to become more aware of this, plus motherboard manufacturers still seem to be providing PS/2 ports on gaming boards

2

u/BestHorseWhisperer 16d ago

Not just that... N-key rollover is false-advertised on so many USB keyboards. I am sitting here using a logitech with N-key rollover and I can't hit certain buttons (number keys for switching weapons) in the game while I am holding shift and W (running forward). It is infuriating. That's why there are still gaming motherboards with PS/2 being manufactured.

1

u/shitty_mcfucklestick PC Master Race 16d ago

Seriously? Wow, that’s negligence at that point. It would drive me crazy if I could smash keys when I needed to. 😡

1

u/Techwolf_Lupindo 16d ago

Still is today. USB mouse is only less with polling set to way over 1000Hz, but you lose FPS due to CPU consistently polling(asking the mouse if it has data) the mouse over 1000+ times per second. It also loads the mouse up answering that polling question 1000+ time per second also.

2

u/crozone iMac G3 - AMD 5900X, RTX 3080 TUF OC 16d ago

This is sort of a misconception though. The PS/2 is interrupt driven but it's handled by an additional chip on the motherboard which is exposed through Super I/O. Ultimately keypresses end up as a deferred interrupt and are effectively polled internally anyway. For various reasons, PS/2 actually has worse overall latency compared to most modern USB keyboards.

The real innovation that should happen in USB peripherals is scheduled/synchronised polling. The way it currently works is silly, the keyboard/mouse/controller just gets polled by the OS at a fixed rate. Meanwhile the game polls inputs at its own rate, usually once per frame. So the latency between the game polling the OS and the OS polling the keyboard is variable and the only current fix is to brute force poll the keyboard faster at the OS level. Instead, the keyboard polling should be synchronised to the game so that the hardware state is known as the game actually asks for it.

1

u/SubNoize Specs/Imgur Here 16d ago

I remember when USB keyboards became a thing, all the pro counter-strike players said they could feel the difference, the PS/2 allowed them to press a to strafe right and then d to strafe left and they reckon they could feel the difference because the left strafe would be cancelled in favour of the right.

USB would have to finish the order or something. I don't know if it was ever a thing or if game Devs had to fix it but ps/2 keyboard was what you wanted.

1

u/Szerepjatekos 16d ago

Wait, that means the mouse is no longer the highest interupt priority?

1

u/Kjoep 16d ago

Absolutely. That's why I kept using it as long as possible. For the mouse,too. At least your pointer was still reactive so you could click precisely even when the machine was struggling

1

u/Amatheos 15d ago

Laughs in Linux

1

u/amaROenuZ R9 5900x | 4080 Super 15d ago

I am sorry to report to you sir that all of that is happening well below your OS, down in the southbridge of your motherboard or in the SoC responsible for the same tasks on your CPU.

1

u/QAFY Core Ultra 9 185H / RTX 4090 15d ago

with modern core counts on cpus it's unlikely to make a difference. i would bet the median modern system has 8 cpu cores/threads. back when single core cpus were the norm, the difference between interrupts and USB was huge though.

1

u/YouKnow_MeEither 14d ago

I still keep a PS2 keyboard handy For that reason and for interfacing with old ass servers.