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MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

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MX-16_fan
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MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#1 Post by MX-16_fan » Sat Sep 22, 2018 8:03 am

@all:

Helping a friend to tidy up a chaotic collection of old PC cables piled up in his cellar, I discovered two old PS/2-to-USB adapters. One of them was colored green and had a mouse symbol on it. The other one was purple-colored and had a keyboard symbol on it.

As both adapters offered what looked like a standard USB port, this led me to the question whether you can do anything with a PS/2 port (using MX-17.1) other than connecting a mouse or a keyboard to it. I was thinking of, e.g., charging a smartphone, or printing (via some serial adapter).

According to my friend's machine's manual, its PS/2 port can (without an adapter) be used for either a mouse or a keyboard. My friend (like many people) has a number of office peripherals but never seems to have enough free periphals ports. So using the PS/2 slot would actually make sense. Besides, it would be great fun to see it being used for some not-so-often-seen purpose :happy:.

Any answer will be greatly appreciated.


Greetings, and a nice weekend to all of you, Joe

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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#2 Post by dolphin_oracle » Sat Sep 22, 2018 8:44 am

I don't think you would want to use a PS/2 port for anything other than a keyboard. The system still sees a USB-to-PS/2 adapter as a PS/2 port (at least I think so), so you wouldn't be able to use it for anything anyway. you used to see these things all the time when the keyboard manufacturers were migrating to USB but there was still a huge installed-base of PCs with PS/2 ports.

keep in mind that PS/2 ports are also not designed to be unplugged while the PC is powered on. you can hose a motherboard doing that, so if you experiment, be very careful.

serial and parallel ports are much safer to work with.
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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#3 Post by MX-16_fan » Sat Sep 22, 2018 9:43 am

@dolphin_oracle:
dolphin_oracle wrote:
Sat Sep 22, 2018 8:44 am
(...)
keep in mind that PS/2 ports are also not designed to be unplugged while the PC is powered on. you can hose a motherboard doing that, so if you experiment, be very careful.
(...)
Thanks for the warning. Already did that, but only the adapter itself (to see if it fits), with no actual USB device attached. Is that likely to have damaged the hardware?


Greetings, Joe

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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#4 Post by dolphin_oracle » Sat Sep 22, 2018 9:49 am

Just be careful. We had a guy in our office some years ago that went through computers pretty fast. We tracked it down to his cleaning schedule. He would unplug his his keyboard and mouse when he pull out his tower to clean behind it. It didn't catxh him every time but it got him enough that we did some research. The quality of the motherboard probably makes a big difference. His was lowish quality.
http://www.youtube.com/runwiththedolphin
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FYI: mx "test" repo is not the same thing as debian testing repo.

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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#5 Post by MX-16_fan » Sat Sep 22, 2018 12:48 pm

@dolphin_oracle:
dolphin_oracle wrote:
Sat Sep 22, 2018 9:49 am
Just be careful. We had a guy in our office some years ago that went through computers pretty fast. We tracked it down to his cleaning schedule. He would unplug his his keyboard and mouse when he pull out his tower to clean behind it. It didn't catxh him every time but it got him enough that we did some research. The quality of the motherboard probably makes a big difference. His was lowish quality.
Would one instantly notice any damage done to the mainboard, or could you just as well encounter increased instability every now and then? Greetings, Joe

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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#6 Post by timkb4cq » Sat Sep 22, 2018 1:14 pm

Normally one would see it right away - however I have seen some weird behavior on old (pre-pentium) machines with damaged ps2 ports. The IBM PC keyboard controller was hooked to the CPU A20 line. Due to an IBM hack when the IBM AT using the 286 processor was introduced, the A20 line also affected memory addressing. This could lead to random lockups & reboots if the keyboard controller was damaged but not completely kaput.

Current motherboard architectures have the ps2 port combined with USB controller and are far more robust in this respect. I still don't recommend hotplugging ps2 devices but damage is a lot less likely.

BTW, the USB/ps2 adapters are not all the same. It depends how the keyboard or mouse manufacturer that included them dealt with the two protocols in their devices.
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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#7 Post by MX-16_fan » Sat Sep 22, 2018 2:10 pm

@timkb4cq:
timkb4cq wrote:
Sat Sep 22, 2018 1:14 pm
(...)
Current motherboard architectures have the ps2 port combined with USB controller and are far more robust in this respect. I still don't recommend hotplugging ps2 devices but damage is a lot less likely.
Thanks! Glad to hear I probably didn't damage my friend's beloved old machine - he wouldn't particularly like that.

Just out of curiosity: What year did the "current" design you mentioned become the usual, approximately?


Greetings, Joe

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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#8 Post by timkb4cq » Sat Sep 22, 2018 2:49 pm

Hard to give a precise date with all the different variations, but Intel split the keyboard controller & usb (and a bunch of other stuff) into their PCH (platform controller hub) circa 2008. AMD did something similar with the FCH (fusion controller hub) circa 2010.
Those moves gave the improved isolation over the older direct Southbridge or Southbridge/SuperIO chip setups.

In any case, just plugging in a ps/2 to usb adapter with no keyboard or mouse plugged into it wouldn't damage a motherboard. The adapters are purely passive.
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Re: MX-17.1: What can you use a PS/2 port for (other than connecting a mouse or a keyboard to it)?

#9 Post by MX-16_fan » Sat Sep 22, 2018 5:05 pm

@timkb4cq:
timkb4cq wrote:
Sat Sep 22, 2018 2:49 pm
(...)
In any case, just plugging in a ps/2 to usb adapter with no keyboard or mouse plugged into it wouldn't damage a motherboard. The adapters are purely passive.
Good to know, thanks. Greetings, Joe

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