Parity vs. non-parity for linux ??

Parity vs. non-parity for linux ??

Post by Michael Wright ED » Sat, 26 Oct 1996 04:00:00



Should I buy parity or non-parity SIMMs to upgrade my linux box?

Michael

--

NASA/MSFC/ED23          Huntsville AL 35812
(205) 544-1544          FAX: (205) 544-3554

 
 
 

Parity vs. non-parity for linux ??

Post by Albert D. Cahal » Sat, 26 Oct 1996 04:00:00



Quote:> Should I buy parity or non-parity SIMMs to upgrade my linux box?

Forget parity if you will use a PC. Parity RAM is slower, more
expensive, and does not help you much. Using it will limit your
choice of motherboards to those few that really check parity.

Parity RAM is supposed to provide error checking. In a PC, a parity
error generates an NMI. Linux will report the NMI, but there is no
way to be sure that the NMI was not caused by something else, such
as powersaving junk. There is no way to locate the bad memory.

Parity memory will not detect many common types of errors. When the
address lines don't always work, parity won't help. When the data
gets corrupted before storage, parity won't help. You can discover
more errors with a _good_ memory checker program (look on sunsite
for one that boots from a floppy) or by compiling several kernels
at once many times in a row.
--
--
Albert Cahalan
acahalan at cs.uml.edu (no junk mail please - I will hunt you down)

 
 
 

Parity vs. non-parity for linux ??

Post by bill davids » Thu, 31 Oct 1996 04:00:00





|
| > Should I buy parity or non-parity SIMMs to upgrade my linux box?
|
| Forget parity if you will use a PC. Parity RAM is slower, more
| expensive, and does not help you much. Using it will limit your
| choice of motherboards to those few that really check parity.

That's not the way it works, you're thinking about something else.

Parity RAM is not slower, 70ns RAM is 70ns RAM, etc. The parity is
done in a separate ciruit which doesn't affect the access time. It
is (slightly) more expensive, and has the advantage of being capable
of ECC (error correcting) operation if your needs change. I think
that's what you're remembering, ECC in most cases does slow the
memory access by some factor (1 w/s if I remember Intel specs).
|
| Parity RAM is supposed to provide error checking. In a PC, a parity
| error generates an NMI. Linux will report the NMI, but there is no
| way to be sure that the NMI was not caused by something else, such
| as powersaving junk. There is no way to locate the bad memory.

Parity is supposed to detect errors, not to locate them. Having
never gotten an NMI caused by anything other than memory, I'll take
your word for this, although the motherboard typically only hooks
the parity to NMI, so you may be using something on your bus which
has problems.
|
| Parity memory will not detect many common types of errors. When the
| address lines don't always work, parity won't help. When the data
| gets corrupted before storage, parity won't help. You can discover
| more errors with a _good_ memory checker program (look on sunsite
| for one that boots from a floppy) or by compiling several kernels
| at once many times in a row.

I don't know what you see as a "common" error, I'm working with an
app which uses 350+ PCs running on four continents, and the single
most common failure is a bad memory part.

I always liked parity even on DOS machines, where you get a hard
crash on parity. I can live with a system failure better than I can
with corrupted data. Even EDO comes in parity if you look a bit.
--

  What do you mean I shouldn't do thing like that at my age?
  At my age if you don't do things like that you might die of natural causes!

 
 
 

1. parity vs. non-parity memory ???

I want to add another 16MB of RAM to my PC for running X apps.
I currently have 16MB of parity RAM on a SIMM-SAVER.

Should I buy a 16MB parity or non-parity SIMM?  Any suggestions
on who has the best mail-order prices?

Thanks, Michael

--

NASA/MSFC/ED23          Huntsville AL 35812
(205) 544-1544          FAX: (205) 544-3554

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