You may receive the following error message while running
STOP 0x0000007F (UNEXPECTED_KERNEL_MODE_TRAP)
This error message can occur if either of the following
- Your computer has hardware or software problems (hardware
failure is the most common cause).
- You try to over clock the speed of your computer's
processor (for example, you set a 150 MhZ processor to run at 187
The above STOP error means a trap occurred in kernel mode and
the trap is either one the kernel is not allowed to have or is always fatal.
The most common causes of a STOP 0x7F are:
- Low-level hardware corruption, such as corrupt memory
- Mismatched memory modules
- A malfunctioning motherboard
To determine an approximate cause, examine the parameters at
the top of the STOP screen:
**STOP 0x0000007F (0x000000XX, 0x00000000, 0x00000000, 0x00000000)
The most important parameter is the first one (0x0000000X) which
may have several different values. The cause of this trap can vary, depending
on the value of this parameter. All traps that cause a STOP 0x7F can be found
in any Intel x86 microprocessor reference manual as they are specific to the
x86 platform. Here are some of the most common ones:
0x00000000 Divide by Zero Error
0x00000005 Bounds Check Fault
0x00000006 Invalid Opcode
0x00000008 Double Fault
Divide by zero error
A divide by zero is caused when a DIV instruction is executed and
the divisor is 0. Memory corruption (or other hardware problems) or software
failures can cause this.
The overflow instruction occurs when the processor executes a
call to an interrupt handler when the overflow (OF) flag is set.
Bounds check fault
This fault is generated when the processor, while executing a
BOUND instruction, finds the operand exceeds the specified limits. A BOUND
instruction is used to ensure that a signed array index is within a certain
This fault is generated when the processor attempts to execute an
invalid instruction. This is generally caused when the instruction pointer has
become corrupted and is pointing to the wrong location. The most common cause
of this is hardware memory corruption.
A double fault occurs when an exception occurs while trying to
call the handler for a prior exception. Normally, the two exceptions can be
handled serially, however there are several exceptions that cannot be handled
serially and in this situation the processor signals a double fault. The two
primary causes for this are hardware and kernel stack overflows. Hardware
problems are usually related to CPU, RAM, or bus. Kernel stack overflows are
almost always caused by faulty kernel-mode drivers.
To resolve this issue, use the appropriate method:
- If either software or hardware can cause a particular trap,
a debug is required to determine which is the cause. If you suspect a hardware
problem, try the following hardware troubleshooting steps:
- Test the RAM in the
computer by running the diagnostic software that is provided by the computer manufacturer. Replace any RAM that is reported as bad. Also, make sure that all the RAM in the
computer is the same speed.
- Try removing or swapping out controllers, cards, or
- Try a different motherboard on the computer.
- If you are over clocking the speed of your processor, set
it back to the speed at which it is designed to run.
- Check with the hardware vendor for any updated hardware
drivers or BIOS updates, or both.
For more information on processor faults, consult an Intel
processor reference manual.