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Date:      Wed, 17 May 1995 18:40:22 -0700 (PDT)
From:      "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com>
To:        karl@bagpuss.demon.co.uk (Karl Strickland)
Cc:        freebsd-hardware@FreeBSD.org
Subject:   Re: bad memory..
Message-ID:  <199505180140.SAA13066@gndrsh.aac.dev.com>
In-Reply-To: <199505180040.BAA03026@bagpuss.demon.co.uk> from "Karl Strickland" at May 18, 95 01:40:07 am

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> 
> system: 486/33 isa, aha1542, 16mb
> 
> added another 16mb and it went crazy with programs dumping core, and
> kernel traps all over the place.  so i suspect the memory is bad (this
> machine has run with 20Mb previously, and has bounce buffers configured
> etc)..
> 

Try adding 1 wait state to the memory setup in the BIOS if you can.  I
found that my ECS EISA/VLB board would run on ``fastest'' with 4 4MB-60nS
simms, but add 4 more and I had to slow it down to ``faster''.  This
is the same as adding 1 wait state to main memory cycle times.


> On FreeBSD 1.x, the memory test doesnt complain.  I remember reading
> the BIOS's memory test is crap.  What should I use to test memory?

FreeBSD is one heck of a memory tester, but it does not point to the
location of the failure.  You *should* get an NMI for a parity error,
but gross memory failure (ie 2 bit or more) is often missed by this
type of logic.

> (currently the machine has 4x4Mb 30 pin 9-chip simms, giving 16Mb.
>  the new 16Mb is 4x4Mb 30 pin 3-chip simms.  that shouldnt cause
>  any problems right?)

No, that should not cause a problem.  Are the memory simms the same
speed, and at least 70nS or faster?  What motherboard is this?



-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                   Custom computers for FreeBSD



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