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NMI defined: Non Maskable Interrupt - An interrupt which cannot be disabled
by clearing the CPU's interrupt enable flag,
unlike most normal interrupts. Non Maskable
Interrupts are typically used to signal calamities
which require immediate action, such as a parity
error, a hardware failure, or imminent loss of
power. In the MS-DOS/BIOS Interrupt Vector Table
the address for the handler of the Non Maskable
Interrupts is stored at position 02H; this is why
a NMI is often referred to as INT 02H.
Parity Error defined: In a machine with parity
protected memory, for each memory location there
are 9 bits; 8 of them are used to store the value
and one is used to store the parity bit. When a
value is written in memory, the hardware counts
the number of ones and store a one or a zero in
the parity bit, according to the parity of ones
found in the memory location. When the same
location is read, the hardware re-computes the
parity bit and compares it with the one stored
in memory. If they are different a parity error
is generated.
NMI Explained - by Jan Bottorff. This
short, yet thorough article hits the nail on the
head. A must-read if one wants to grasp the root
of NMI errors.
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Microsoft's take on the error for Windows XP, including
several suggestions for fixes
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Microsoft's take on the error for Windows 2000, NT, and NT Server, fixes
included as well
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Microsoft's take on the error for Windows 3x, fixes
NOT included.
This link however gives a thorough general
overview over the causes of Parity errors, that are
well worth a read.
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This article on Microsoft's site discusses the
extensive study in determining the causes of some
NMI Memory Parity Errors in Windows with the aid
of a high tech SIMM tester. The results are not
conclusive and the research into this is ongoing.
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PC Guide article 1 and
2
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Dell Hints and Tips: They show step-by-step here how to exchange RAM - given that
a RAM incompatibility is really the root of the error
Forums:
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HP forum post: OS - Win 2000 Server, offers possible fix
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Dell forum post: suggestions range from memory card problems to
power outages - contains links to memory diagnostics programs
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Softrigger forum: MS Knowledge base article vs. exchanging memory
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Compaq forum post 1 and
2: while there are numerous posts in the Compaq forums referencing the error, most of Compaq's "Experts" only
advise to go check out the Microsoft troubleshooting links above. Link 2 has extensive comments on variations of error causes
that are worth a read though.
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