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Date:      Thu, 27 Jul 95 12:54:28 MDT
From:      terry@cs.weber.edu (Terry Lambert)
To:        nik@blueberry.co.uk (Nik Clayton)
Cc:        questions@FreeBSD.org
Subject:   Re: Pentiums and cache problems
Message-ID:  <9507271854.AA07822@cs.weber.edu>
In-Reply-To: <199507271147.LAA01078@elbereth.blueberry.co.uk> from "Nik Clayton" at Jul 27, 95 11:47:52 am

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> Can anyone provide technical information as to the nature of the
> problems concerning some motherboards and the processor cache?
> 
> My Pentium (100Mhz) has two caches, one external, one internal.
> 
> During my intial install of FreeBSD, they were both on. The install
> would randomly reboot at about halfway through. Turning off the external
> cache fixed this problem.
> 
> However, with the internal cache on, I still get the occasional reboot,
> particularly if there is extensive disk activity.

What chipset does the board use?

If Saturn/Neptune/Mercury, what is the chipset manufacture date?  If
prior to Apr 1994, request that they replace the chips with chips
manufactured from masks produced later than Apr 1994.

The typical problem where disabling the cache fixes the bug is that
bus mastering DMA transfers to memory by disk controllers do not cause
the cache contents to be updated or invalidated, and when the "stale"
data is subsequently accessed, you have problems.

The other possibility is faulty electronics on the board itself
preventing cache notification from operating.

The least likely possibility (but it is still a possibility) is
that your cache is actually failing, either because they used slower
than needed parts or because of thermal breakdown from the inside
the case teperate being too high.  Are you running a fan on the
Pentium itself as well as a fan on the case?

Other than that, I can't think of anything serious that could be
going on (off the top of my head).


					Terry Lambert
					terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.



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