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Installing Windows 95B or 95C on Fast Systems

Last reviewed: March 2004

Errors installing, or first run of, Windows 95B or 95C on fast systems.

The following errors may occur when installing Microsoft Windows 95 (OSR1 or OSR2) on any computer with a AMD K6-2 (350MHz or faster), Intel Pentium III (1-GHz or faster) or a Intel Pentium 4 (any).

  • Device IOS failed to initialize. Windows Protection Error. You must reboot your computer.
  • Windows Protection Error. You must reboot your computer.
  • While initializing device IOS: Windows protection error.

Microsoft have supplied a patch that corrects this problem (Q192841). Microsoft says this patch applies to AMD K6-2 processors but it also applies to other chips such as the Intel Pentium III (1-GHz or faster) and all Pentium 4 processors.

Note: This fix applies only to Windows 95B & C (OEM 2.x)
Note: The fix does not correct the problem for the retail version of Windows 95.
Note: This does not apply to Win98, 98SE, or Me which come already fixed.

The patch does have an inbuilt uninstall feature.

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THE PROBLEM

Software timing:

The patch (amdk6upd.exe) fixes a software timing loop that is sensitive to processor frequency. It is not a processor error.

The error is a result of a divide exception in IOS.VXD, or a similar error within ESDI_506.PDR or SCSIPORT.PDR. Those files, and other associated files, must be updated.

The problem usually occurs during installation, or re-installation, of Windows 95.

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THE PATCH: Windows 95 Update for Fast CPUs

Amdk6upd.exe:

Microsoft designed this update (Amdk6upd.exe) to be run from Explorer in Safe Mode. However some users can not get to Safe Mode after installing Win95B or C with a fast processor. Fortunately, a look at amdk6upd.exe using /? shows it can easily be extracted to a floppy.

Don't let the file name deceive you! It was named prematurely. It does work with other chips.

The Amdk6upd.exe patch installs/replaces 9 (or 8) files to your Windows 95B or C (details below).
One file, Ntkern.vxd, is replaced only if the version of Windows 95 is OSR2.1 or OSR2.5

This fix is only for Windows 95B & C (OEM SR versions 2, 2.1, and 2.5).

The fix does not correct the problem for the retail version of Windows 95, and does not apply to Win98, 98SE, or Me which come already fixed.

Caution: There's no guarantee that this fix will work for all users.

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IDENTIFY your Windows Version

Use System Properties

If you can get to Safe Mode you can use System Properties.
Right-click on My Computer and select Properties.
Under the General tab, look at the System:

If you have a boot disk made by that Windows, you can boot with it and type VER at the DOS prompt.

An OEM SR2 system will show as 4.00.9500 B or 4.00.9500 C as the version. The number may vary slightly, but the letter will be a B or a C for the OSR2 version.

INSTALLING Amdk6upd.exe

You have three options:

Option #1: From Safe Mode
Install the patch using Windows Explorer from Safe Mode as recommended by Microsoft. However, if you can not get to Safe Mode after the install then you must use Options 2 or 3.

Option #2: From Bootable Floppy & True DOS
If you can not get to Safe Mode then install the patch from a bootable floppy that contains the files extracted from amdk6upd.exe

Option #3: Underclock
Experienced users can try underclocking the CPU prior to the install.

Option #1 is obviously the first choice and will work for many users.

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OPTION #1: Safe Mode

Installing the Amdk6upd.exe patch from Safe Mode:

This is the method described by Microsoft in Microsoft Knowledge Base reference article(s):
Q192841 AMD K6-2/350 CPU Windows Protection Error at boot time
http://support.microsoft.com/support/kb/articles/Q192/8/41.ASP

1. Download the Amdk6upd.exe file to a floppy disk. Download the file from another computer, if necessary.

2. Restart your computer. When you see the Starting Windows 95 message, press the F8 key, and then choose Safe Mode from the Startup menu.

3. If your computer starts in Safe mode, skip to step 6. If you cannot start Windows, continue with steps 4 & 5.

4. Restart your computer again. When you see the Starting Windows 95 message, press the F8 key, and this time choose Command Prompt Only from the Startup menu.

5. At the c:\ prompt, type win /d:m to start Windows in Safe mode.

6. Insert the floppy disk containing the Amdk6upd.exe file you downloaded in step 1, and then use Windows Explorer or My Computer to double-click the file.

7. Follow the instructions on the screen to install the update.

You may be warned that you are about to replace a newer file with an older version of the file. Generally, you should the keep the newer file, and choose not to replace it with an older file.

You must use Option #2 or #3 if you fail to get to Safe Mode.

Download Amdk6upd.exe now

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OPTION #2: From Bootable Floppy & True DOS

When you can not get to Safe Mode:

1. You need a basic boot disk with at least 486 KB free space on it.

2. Download the Amdk6upd.exe patch (use a friends computer, if necessary). Do not run it.

3. Use your friends WinZip to extract the files from AMDK6upd.exe to the bootable floppy disk.
    or extract its files to the bootable floppy by executing AMDK6upd.exe /T:a:\ /C

4. Start Windows 95 installation following the normal procedure.

5. When the error occurs (usually on the first boot into Windows 95), or the computer fails to start Windows 95, bootup using the bootable floppy used in Step 3.

6. Manually copy the updated driver files on the diskette to their proper locations as indicated below:

These go in the C:\WINDOWS\SYSTEM\IOSUBSYS folder:
DISKTSD.VXD
CDFS.VXD
ESDI_506.PDR
HSFLOP.PDR
SCSIPORT.PDR

These go in the C:\WINDOWS\SYSTEM\VMM32 folder:
IOS.VXD
INT13.VXD
VFBACKUP.VXD
NTKERN.VXD

Note: Ntkern.vxd is needed only if the version of Windows 95 is OSR2.1 or OSR2.5

Example:
COPY /V A:\IOS.VXD C:\WINDOWS\SYSTEM\VMM32
if Windows was installed on C:\Windows
(there is a space before each of /V, and A:\ and C:\).

7. Remove the floppy disk and restart the system.

8. If prompted, select Normal Startup of Windows 95.

9. Complete Windows 95 installation procedure if necessary.

10. After Windows 95 is fully installed and running, execute the AMDK6upd.exe without any command switches to register the update.

Download Amdk6upd.exe now

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OPTION #3: Underclock the CPU

Alternative method when you can not get to Safe Mode:

Only Advanced users should consider this option.

1. Download the Amdk6upd.exe patch (use a friends computer, if necessary). Do not run it.

2. Save/Copy the patch to your hard disk. You may need to do so from a bootable floppy.

3. Clock the CPU down to 300 MHz.

4. Do a minimum installation of Windows 95 (do not load any extra drivers, yet).

5. Run Amdk6upd.exe to install the patch.

6. Shutdown, and clock the CPU back up to the correct speed.

7. Reboot, and load necessary drivers.

Not all users will be able to underclock to this extent.

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UNINSTALL files installed by AMDK6upd.exe

According to Microsoft:

Using Windows Explorer, locate the file AMDK6_UN.INF in the Windows\INF\QFE folder,
right-click on the file AMDK6_UN.INF, and choose Install.

You will be prompted for the Windows 95 installation CD or diskettes. Choose the appropriate path.

You may be prompted to replace the newer file with an older version of the file.

To uninstall this update, choose to Replace the newer file(s) with the older file(s).

Restart the computer for the changes to take effect.

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Please remember that you alone are responsible for the consequences of any changes you make to your computer hardware or software.

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