Windows 8 and 8.1 Forums


Windows Registry modification help needed.(i8042prt)

  1. #1


    Posts : 81
    Windows 8.1 64-bit

    Windows Registry modification help needed.(i8042prt)


    Hello,
    My friend had an issue with his PS/2 keyboard, the Num Lock light was on,keyboard was recognized in BIOS, but not recognized in Windows 8, so I was looking for a solution, and I found this:
    Bug?: Windows 8 PS/2 Keyboard not detected after wireless - Microsoft Community ;
    quote of the solution from this link :

    Windows supports both USB and PS/2 keyboards, and can in fact support having more than one such input device plugged in at a time. However, when a PS/2 keyboard is uninstalled and a USB keyboard is made the main input device (via the Keyboard section in the Control Panel), PS/2 keyboard support is disabled.This can be frustrating if a user needs to plug a PS/2 keyboard back in to perform debugging in Windows, or when a USB keyboard no longer works correctly due to problems with the USB subsystem. Note: A PS/2 keyboard will still allow access to the BIOS and will work in the boot-loader; it just won't work correctly in Windows. (It will, however, usually work in the Recovery Console.)
    PS/2 keyboard devices are governed by a kernel-level service called i8042prt, short for the technical name for the PS/2 keyboard port. When a USB keyboard is added as a replacement for a PS/2 keyboard, the i8042prt service is forcibly disabled. This is to prevent a conflict between PS/2 and USB devices, but if a PS/2 keyboard is reinstalled, the service is not automatically restarted.
    To switch back to using a PS/2 keyboard, the user needs to edit the Registry to restart thei8042prt service. To do this, InHKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt,, edit the Startvalue and set it to a hex or decimal value of 1. Reboot and change to a PS/2 keyboard via the Keyboards section in Control Panel.
    I followed the instruction, edited 'Start' value to 1 (using a USB keyboard ) and it worked! now PS/2 keyboard is working!
    But what I've also noticed is that I restarted Windows with Windows update just before connecting the PS/2 keyboard.
    So now I am afraid that what actually solved it was the Windows update, and not changing the registry value.
    What do you think solved the problem? Windows update or the 'i8042prt' registry editing? because I don't want to mess his computer by changing registry values which I have no idea what they're doing.
    I need your help if you know about this 'i8042prt' registry and whether I can leave its 'Start' value at '1' instead of the default value. By the way, what was the default value of 'Start' in 'i8042prt' if I wish to restore to default?

    Thanks!

      My System SpecsSystem Spec

  2. #2


    Sloe Deth, Californicatia
    Posts : 3,908
    Windows 8 Pro with Media Center/Windows 7


    Any time you change a mouse and keyboard, Windows 8 has to re-detect it. I'll have to read that article in the link you posted, I usually don't trust posts in the MS Community. I think it was your Windows Update as well, rather than the reg key change. I've simply never had to do it, and I switch from PS/2's to USBs and back all the time. I'll have to test this out on my other machine and see it it detects a PS/2 KB.

    If you are going from a USB KB to a PS/2 KB, it may cause this issue. But usually, once the Computer gets connected to the Net, it will download any driver it needs and install it, it may take a reboot to apply the PS/2 Keyboard.

    I'm going to try it now, and I'll be back in a bit to tell you the results, I have Windows 8 that was installed with a USB KB, I'm going to switch it to a PS/2 and see what happens. It should detect after a short while.
      My System SpecsSystem Spec

  3. #3


    Sloe Deth, Californicatia
    Posts : 3,908
    Windows 8 Pro with Media Center/Windows 7


    Ok, I just rebooted my Media system, which has never been set up to use a PS/2 Keyboard, with a PS/2 Keyboard. It detected right away. I don't know why it would say PS/2 would be disabled, cos if that were true, it should have been disabled the whole time, cos I had never used a PS/2 KB or mouse in this system.

    Or does this only happen when you start with a PS/2 then change to USB and then try to change back? That just does not make sense. I'll give it a try on my other system.

    Regardless, once you shut off your system, change input devices, and restart, it should automatically detect and switch to that device. At NO time should you ever delete any unused Keyboard drivers.

    You may want to check that system's BIOS, because sometimes you can "Disable" the PS/2 Inputs. That may have been the case.


    [Edit] I checked for that i804p2 setting on the Reg in both of my systems and there is NO "StartValue" key in either of them. This system uses PS/2 devices and my other system uses USB devices. So I don't know what that refers to, it may be for an earlier version of Windows.
      My System SpecsSystem Spec

  4. #4


    As the rule of thumb, PS2 devices have to be connected at the time before the boot, USB ones you can shuffle as you please. In some BIOSs there are settings to disable PS2 ports and in some there is a setting for "Legacy USB" to which most keyboards and pointing devices belong.
      My System SpecsSystem Spec

  5. #5


    Posts : 81
    Windows 8.1 64-bit


    Quote Originally Posted by XweAponX View Post
    Ok, I just rebooted my Media system, which has never been set up to use a PS/2 Keyboard, with a PS/2 Keyboard. It detected right away. I don't know why it would say PS/2 would be disabled, cos if that were true, it should have been disabled the whole time, cos I had never used a PS/2 KB or mouse in this system.

    Or does this only happen when you start with a PS/2 then change to USB and then try to change back? That just does not make sense. I'll give it a try on my other system.

    Regardless, once you shut off your system, change input devices, and restart, it should automatically detect and switch to that device. At NO time should you ever delete any unused Keyboard drivers.

    You may want to check that system's BIOS, because sometimes you can "Disable" the PS/2 Inputs. That may have been the case.


    [Edit] I checked for that i804p2 setting on the Reg in both of my systems and there is NO "StartValue" key in either of them. This system uses PS/2 devices and my other system uses USB devices. So I don't know what that refers to, it may be for an earlier version of Windows.

    Canyou please checkHKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt, (noti804p2?) there is no "StartValue" but just "Start".. can you please check it again to tell me what is your defaultnumber there ? because I changed it to 1 like mentioned in the MScommunity forums. Also, I did not delete any unused keyboard driver,or maybe you mean that when I changed the "Start"on HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt, itdeleted the drivers? (sorry I really don't know what putting "1"in "Start" in i8042 registry does)


    Quote Originally Posted by CountMike View Post
    As the rule of thumb, PS2 devices have to be connected at the time before the boot, USB ones you can shuffle as you please. In some BIOSs there are settings to disable PS2 ports and in some there is a setting for "Legacy USB" to which most keyboards and pointing devices belong.

    I didn't see in bios an option to disable ps/2, and I know about the rule of thumb of ps2 devices, so I did plug them before booting.. and it didn't work either.. only after I did as mentioned in the MS forum. but now I don't know what actually solved it, and what should I do with the "Start" I changed earlier, should I leave it at "1" or change it back to what it was..I'm afraid it might affect the pc in future?
    ?
      My System SpecsSystem Spec

  6. #6


    Posts : 959
    Windows 8.1, 10


    Quote Originally Posted by CountMike View Post
    As the rule of thumb, PS2 devices have to be connected at the time before the boot, .
    I think the culprit here is Windows 8's "fast Startup" which is enabled by default.

    When you shut down a Windows 8 PC with default settings, you aren't doing a "full" power off. You're actually just hibernating some parts of the operating system.

    So when you shut down the PC and switch it on again, I'd bet that PS/2 ports don't count this as a proper "boot" and therefore it won't notice if you've plugged a keyboard in.

    However a restart does a more thorough shut down, which is why that Windows Update had an effect,

    If you enter this command at a command prompt or via <>+<R> (save documents and close down other software first, as it's quick) it will do a "real" switch off, and if you plug in the keyboard before switching on again, I suspect the PS/2 port will be scanned and work:
    Code:
    shutdown.exe /s /f /t 00
      My System SpecsSystem Spec

  7. #7


    Sloe Deth, Californicatia
    Posts : 3,908
    Windows 8 Pro with Media Center/Windows 7


    I think David hit it on the head, the system in question may have been in Hibernation. Make sure the system is totally shut down before adding a PS/2 device.

    I checked 2 Windows 8 systems, that registry entry simply is not there. One has USB KB and Mouse, the other, PS/2 KB and mouse. Sorry, nope it's not there.
      My System SpecsSystem Spec

  8. #8


    Posts : 81
    Windows 8.1 64-bit


    Quote Originally Posted by DavidY View Post
    Quote Originally Posted by CountMike View Post
    As the rule of thumb, PS2 devices have to be connected at the time before the boot, .
    I think the culprit here is Windows 8's "fast Startup" which is enabled by default.

    When you shut down a Windows 8 PC with default settings, you aren't doing a "full" power off. You're actually just hibernating some parts of the operating system.

    So when you shut down the PC and switch it on again, I'd bet that PS/2 ports don't count this as a proper "boot" and therefore it won't notice if you've plugged a keyboard in.

    However a restart does a more thorough shut down, which is why that Windows Update had an effect,

    If you enter this command at a command prompt or via <>+<R> (save documents and close down other software first, as it's quick) it will do a "real" switch off, and if you plug in the keyboard before switching on again, I suspect the PS/2 port will be scanned and work:
    Code:
    shutdown.exe /s /f /t 00
    Quote Originally Posted by XweAponX View Post
    I think David hit it on the head, the system in question may have been in Hibernation. Make sure the system is totally shut down before adding a PS/2 device.

    I checked 2 Windows 8 systems, that registry entry simply is not there. One has USB KB and Mouse, the other, PS/2 KB and mouse. Sorry, nope it's not there.
    Thanks for letting me know about Windows 8 hibernation restart.. but .. did you open regedit and went to this full path :
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt?
    How come you do not see this i8042prt? are you sure you're looking at the correct place? in regedit? type in Search regedit and go to this path and you will see 'Start' just like in the MS community forum directions, you must be doing something wrong if you don't find it..
      My System SpecsSystem Spec

  9. #9


    Sloe Deth, Californicatia
    Posts : 3,908
    Windows 8 Pro with Media Center/Windows 7


    That's where I looked, no StartValue key at all. Not in Windows 7 either. All that is there is EventMessageFile and TypesSupported.
      My System SpecsSystem Spec

  10. #10


    Posts : 959
    Windows 8.1, 10


    For info here's what that bit of Registry looks like on my laptop.

    It doesn't actually have a physical PS/2 port so I don't know how much help this is.
    Click image for larger version

    You'll see that Start is set to 3 for me, but for all I know it isn't the right setting to support PS/2, and without the hardware I can't test it.

    Is there any error or anything like it within one of the Device Manager tabs?
    Click image for larger version
      My System SpecsSystem Spec

Page 1 of 2 12 LastLast
Windows Registry modification help needed.(i8042prt)
Related Threads
Hello, The first question I can imagine you are thinking is what am I talking about or why? : ) For a project I am working on we are using Windows 8.1 with SATA configuration in IDE. Not AHCI. A few years ago you use to be able to go to the following Hard Disk Controller ClassGuid ...
Windows 8.1 x64 BSOD [Registry Error] in BSOD Crashes and Debugging
Hello, I'm getting at random times this BSOD in my laptop. It happens 100% of the time when i leave the laptop idle. I receive the BSOD too as soon as i press the defrag hard drive button. Any thoughts? 54276
For those who have read the posts on System Restore failed, but are running Windows 8.x, I also found a solution for my registry problem. When running Windows 8.1 x64 a copy of the registry information is saved in c:\windows\system32\config\RegBack so you can make a copy of these registry files...
Hi I'm new to Windows 8 and helping someone with a couple of things on their new laptop which was recently upgraded from Windows 8 to 8.1 One issue might involve a registry edit so I began to look in the registry but I've noticed something odd when I run regedit. Each time I run it, what...
Hi, I need help disabling Windows 8 firewall through registry. Thanks.
Hi all! I am seeing some vague references to older Windows versions automatically backing up the registry at startup and saving the backup in some folder... Can't really find out any more. Does anyone have definite information about this in Windows 8, and where any such backups can be found? ...
If anyone has Windows 8, can one go into the Registry and Find RunMRU and see if you have a file called "control/1" - I had someone do a bit of work in my Registry this morning and am hoping the guy was legit. Does that file appear to be correct? Also, I notice when go to Paste something in...
Eight Forums Android App Eight Forums IOS App Follow us on Facebook