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Repairman45
Blue Screen Again
Posts: 4
Registered: ‎10-29-2018
Location: US
Views: 605
Message 1 of 2

Adding a PS/2 port to a ThinkCentre M83 Previously Using USB Keyboard and Mouse

Machine: Lenovo ThinkCentre M83 Model 10AL000GUS.

In late 2018, some folks still want a computer with PS/2 keyboard and mouse ports. Even Lenovo is offering PS/2 in the recently introduced  Thinkstation P920 workstation, so there must still be good reasons to use PS/2. I wanted to install PS/2 ports by breaking out the knockout on the back of my M83 and installing the PS/2 cable and socket assembly.

There are all sorts of articles on the web talking about the fact that once someone uses a USB keyboard and mouse on a dual-standard PC, the PS/2 ports become disabled. In help forums discussing restoring PS/2 ports, you will often find the suggestion to go into the Windows registry and change an entry for the PS/2 (i8042prt) driver. Background on that driver can be found here:
https://docs.microsoft.com/en-us/windows-hardware/drivers/hid/ps-2--i8042prt--driver
I haven't tried it because I'm afraid I will screw up the registry.

Other help forums advise getting around this problem by buying a USB to PS/2 converter. In fact, Lenovo offers a USB to Dual PS2 cable (FRU# 03T6636, about 19 bucks) to users of certain Tiny Form Factor ThinkCentre computers to provide the optional PS/2 functionality advertised for the machine.

Earlier in this decade, Lenovo was advertising, both in sales brochures and in the user and maintenance manuals, OPTIONAL PS/2 support in many ThinkCentre models. Old parts lists can be found at:
https://support.lenovo.com/us/en/solutions/pd100192
These lists (except for TFF) would have a listing for a "PS/2 (sometimes written as 'PS2') Cable, 170 mm" in the cables section. In the case of my M83, the FRU# is 43N9149. From experience gained from my previous 4 IBM, then Lenovo, computers, I assumed there would be documentation on how to switch from one standard to another. I think that would be a deliverable if you offered to provide PS/2 support for extra money, including how to switch back and forth with USB keyboards and mice from time to time.

Anyway, I bought the 49N9149 cable, removed the knockout for it on the rear of the computer, and mounted it. I connected the cable to the header on the motherboard. The location is shown in the hardware maintenance module for the M83.  I plugged in a known good PS/2 keyboard and mouse, leaving off the old USB devices. The computer booted directly into windows, but the PS/2 devices did not work. I had to re-install the USB keyboard and mouse. I decided I would make sure the new 43N9149 was good and installed correctly, without making any changed to the operating system before making changes to the operating system.

If memory serves correctly, with my older machines I could disconnect the HDD, CD-ROM drive, network cable, etc. and still be able to get into the BIOS to make changes. But after trying every procedure I could find on the web, such as removing the CR2032 battery and following the Clear CMOS / Recovery procedure in the M83 hardware maintenance manual, I still could not access the BIOS utility. I eventually got two error messages with keyboard, mouse, HDD, network cable, and CD-RW drive disconnected:
Error 0211 Keyboard not found, and
Error 0162 Setup Data Integrity Check failure.

Researching further, I eventually came across three web pages which discussed the PS/2 interface on the motherboard:

https://forums.lenovo.com/t5/ThinkCentre-A-E-M-S-Series/Thinkcentre-M58-7360-CTO-KB-MS-mainboard-hea...
http://neighborhoodsupport.net/?x=y:15;m:04
https://superuser.com/questions/927885/what-is-the-end-of-this-cable/927890

After buzzing out the cable, I found an error in the second pinout diagram of the superuser.com page referenced above. Pin 5 is not "No Connection", but acts to sense if the 49N9149 is connected to the computer. Pin 5 on the motherboard side of the 49N9149 cable has a wire on it, and connects to the ground connections inside the socket housing the female PS/2 Hirschmann connectors. This can be seen in the photographs of the 49N9149 on the Lenovo parts listing for this cable assembly, it is one of the two black wires. This is important, because I found out later that if you remove the PS/2 cable from the motherboard while in PS/2 mode, you will be stuck in USB jail.

I eventually got it to work about 3 AM because of an accident. Because of the late hour, here is how I THINK I got it to work. After I buzzed out the cable, I forgot to put it back in. I started doing the Clear CMOS / Recovery procedure in the M83 hardware maintenance manual, with the HDD, CD-RW, Network cable, and USB connectors disconnected. I was getting the 0211 and 0162 error messages. Then I shut down the computer, and connected the 49N9149 cable with PS/2 keyboard and mouse connected. I rebooted, and just got the 0162 error message on the American Megatrends BIOS welcome screen. Hitting F1 got me into the BIOS. So, I saved changes and exited. Then, I shut down the computer from the power switch and reconnected the HDD and CD-RW drives. When I started the computer again, I had to go into BIOS again and do a Save and Exit to clear the 0162 error message, and let Windows boot. But, I now had control with the PS/2 keyboard and mouse. I went into Device Manager> View > Show Hidden Devices. I deleted the entries for the HID keyboard and mouse.

I may have had to perform some of these steps (such as rebooting) more than once (its 3 AM, can't remember everything), but when I went to remount the connector, I unplugged the cable assembly from the motherboard. So, I had to do the procedure over again. Lesson learned: don't ever again disconnect the 49N9149 cable from the motherboard unless you need to do a USB to PS/2 keyboard and mouse changeover.

Lenovo really needs to write a How-To for this series of machines and post it to their support pages on the web.

SeniorGuru
Posts: 2,218
Registered: ‎06-13-2013
Location: US
Views: 574
Message 2 of 2

Re: Adding a PS/2 port to a ThinkCentre M83 Previously Using USB Keyboard and Mouse

You've already mentioned a USB-to-PS/2 adapter as one of the easy recommended solutions, to allow people (such as myself) who like using the old clickety-clack IBM PS/2 keyboards (with the fantastic touch and key-travel and rock-hard cement bottom when the key stops) to continue using them (and their ongoing modern Mexican-manufactured exact duplicate replacements).

 

Some USB-to-PS/2 adapters don't actually support the power requirements of the IBM PS/2 keyboard, but starting in 2012 I was forced to discover one that did since a new PC I was building no longer had PS/2 ports on its motherboard.  And after some search-and-discover, I ran into this Adesso ADP-PU21 adapter which for $15 supports connecting two PS/2 devices (mouse and keyboard) through one USB port on the PC.  It is an "active" adapter, not "passive" (not that it plugs into wall power, but it properly handles the pins), so it properly handles the specific power requirements of the IBM PS/2 keyboard.

 

I have been using it ever since, on several more desktop machines and even on a somewhat complex setup for my P70 laptop on the end of one desk in a "shared" environment that has multiple shared monitors (via multiple inputs from both the desktop and laptop) and one shared IBM PS/2 keyboard (via a KVM switch to which two Adesso adapters are connected).

 

In other words, this Adesso adapter is fantastic.  It just works flawlessly. Period.  And it will solve the objective through an available USB 2.0/3.0 port (even through a USB hub), without dealing with having to deal with trying to accomplish a PS/2 hardware retrofit into a desktop machine.  And of course it also addresses the otherwise impossible hardware upgrade goal of adding PS/2 capability to a laptop.

 

Highly recommended.

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