*BSD News Article 80624


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From: Ken Bigelow <kbigelow@www.play-hookey.com>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Hanging/Crashing FreeBSD.
Date: Sun, 13 Oct 1996 20:42:04 +0000
Organization: Erol's Internet Services
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Message-ID: <3261541C.7A11@www.play-hookey.com>
References: <53bsho$a9a@scooby.beloit.edu> <53qvlq$a7@anorak.coverform.lan>
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Brian Somers wrote:
> 
> In article <53bsho$a9a@scooby.beloit.edu>,
>         walcottt@stu.beloit.edu (Tom Walcott) writes:
> >              I'm using a 486 DX2/66, with 28 megs of RAM; 72 pin 8 mb SIMM,
> > 72 pin 4 mb SIMM, 4 30 pin 4 MB SIMMS.
> 
> Try taking the 72pin 4Mb SIMM out - just to see if the problems go away.
> I suspect that the motherboard expects both 72pin simms to be the same
> size....  I had a board that had 4x30pin slots and 2x72pin - it never
> occurred to me that you could mix the 72pins... I read for a different
> (486) motherboard that you can have one or both of a 72pin pair filled,
> but with both they must be the same simms.
> 

I doubt if it's the 4MB SIMM that's really causing the problem. I am
using three different ISA/VLB motherboards at this time. All three MB
books are explicit that they will allow mixing of 4MB and 16MB SIMMs,
but 8MBs are another matter. One specifically warns against mixing
"double sided SIMMs" with anything else.

The problem is that an 8MB (or 32MB) SIMM requires an odd number of
address lines. Therefore it is actually decoded as two banks of 4MB
(16MB) each. This prevents mixing sizes when these are included in the
mix.

The 30-pin SIMMs are another issue; they are decoded separately.

If Tom really needs the extra memory, I'd suggest investing in a 16MB
SIMM and removing the 8. The 4MB card will coexist nicely with the 16.
-- 
Ken

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