Windows Registry modification help needed.(i8042prt)

mibaup · Aug 6, 2013

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!

XweAponX · Aug 6, 2013

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.

XweAponX · Aug 6, 2013

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.

CountMike · Aug 7, 2013

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.

mibaup · Aug 7, 2013

XweAponX said:
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.

[FONT=Arial, sans-serif]
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)[/FONT]

CountMike said:
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? :huh:?

DavidY · Aug 7, 2013

CountMike said:
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 <:winkey:>+<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

XweAponX · Aug 7, 2013

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.

mibaup · Aug 9, 2013

DavidY said:
CountMike said:

As the rule of thumb, PS2 devices have to be connected at the time before the boot, .

Click to expand...

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 <:winkey:>+<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

XweAponX said:
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..

XweAponX · Aug 9, 2013

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

DavidY · Aug 9, 2013

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.

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?

XweAponX · Aug 9, 2013

OK - I have TWO entries for this - The 2nd one looks as David's does. Still no StartValue Key. Not in Windows 7 either, just checked.

mibaup · Aug 11, 2013

XweAponX said:
OK - I have TWO entries for this - The 2nd one looks as David's does. Still no StartValue Key. Not in Windows 7 either, just checked.

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

DavidY said:
It doesn't actually have a physical PS/2 port so I don't know how much help this is.
View attachment 26089

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?
View attachment 26090

I did not mean "StartValue" I meant just "Start" that you can see 3rd from the bottom on the Registry Editor. ( meant "Start" value because I meant to the value shown near the "Start" I guess that confused everyone

)

jladwig · Aug 16, 2013

i8042 is a system service that controls ps2 mouse and keyboard ports.

Value-Start Type-Description

0-Boot-Specifies a driver that is loaded (but not started) by the boot loader. If no errors occur, the driver is started
during kernel initialization prior to any non-boot drivers being loaded.

1-System-Specifies a driver that loads and starts during kernel initialization after drivers with a Start value of 0 have been
started.

2-Auto Load-Specifies a driver or service that is initialized at system startup by Session Manager (Smss.exe) or the Services
Controller (Services.exe).

3-On Demand-Specifies a driver or service that the Service Control Manager (SCM) will start only on demand.
These drivers have to be started manually by calling a Win32 SCM application programming interface (API), such
as the Services snap-in.

4-Disable-Specifies a disabled (not started) driver or service.

5-Delayed Start-Specifies that less-critical services will start shortly after startup to allow the operating system to be responsive to
the user sooner. This start type was first introduced in Windows Vista.

mibaup · Aug 17, 2013

Thanks for your explanation jladwig! ! !
btw, which number should be the default?

jetroho · Aug 18, 2013

The default value is 3
It should be noted that in the first post the reference to " Startvalue " is a typo . It should have been Start value or correctly , the value Start .

j

jladwig · Aug 18, 2013

Sorry I don't know the default value but from what I've been able to find the default value should be 1. Looks like following the instructions you did set it back to what it should be and is what probably fixed the problem. If there was an update to this driver (can check update history) that fixed the problem it probably set the value correctly and if that value is 1 you would never know what the value was before you changed it.

In the future, if you are going to try and change any registry settings you should make a backup before doing it in case you need to undo or go back. You can also make a back up of individual Registry keys. In your case for example -

Before making any changes right click on the registry setting "Start"
From the context menu select "export"
Will prompt for a name and location to save the file, The file name can be anything you want, but the extension has to be .reg which the export process will put in - Example name: i8042prtstart.reg

Now if you want to undo and put the value back as it was, you can double click on i8042prtstart.reg just as you would to run an application. You will be prompted to confirm you wish to import this into the registry, select Yes or OK. The settings are now back as they were.

jetroho · Aug 18, 2013

Just checked the 4 Win 8 comp's I have at the house . Two have usb kb's two are ps2 . The Start value is 3 on all four machines .
j

jladwig · Aug 18, 2013

Jetroho is correct, checked 2 laptops and this PC that's never had a USB keyboard or Mouse and 3 does seem to be the default value. This does make sense as shown above the driver is started by a call to an API such as New Hardware Detection.

mibaup · Aug 18, 2013

jetroho said:
The default value is 3
It should be noted that in the first post the reference to " Startvalue " is a typo . It should have been Start value or correctly , the value Start .

j

Sorry for the mistake I just didn't know how to write it, from now on I'll sure know how to

, but btw I wrote 'Start' value, with 'Start' under apostrophes, not 'StartValue'

jetroho said:
Just checked the 4 Win 8 comp's I have at the house . Two have usb kb's two are ps2 . The Start value is 3 on all four machines .
j

jladwig said:
Jetroho is correct, checked 2 laptops and this PC that's never had a USB keyboard or Mouse and 3 does seem to be the default value. This does make sense as shown above the driver is started by a call to an API such as New Hardware Detection.

Thanks guys very much for the help!

Windows Registry modification help needed.(i8042prt)

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