Subject: Re: question
From: Mike Tibor (tibor@lib.uaa.alaska.edu)
Date: Sun Sep 22 2002 - 14:20:41 AKDT
On Sun, 22 Sep 2002, Justin Dieters wrote:
> > I always figured that you had to run the same size memory in each slot..
> > in other words you would need 3 - 256's or 3 = 512's. And can you mix
> > types.. dimms and ddrs? Course I don't know much about it.. But curious
> > if that's true or not.
> > Cheers, JD
>
> With the old SIMMS (486's and earlier, maybe some early pentiums?), this
> is true, you need to install them in matching pairs. Nowadays it doesn't
> matter how or where you put your memory (for the most part).
Actually this all boils down to the width of your memory bus. 486's have
a 32 bit memory bus, so a single 72 pin simm (which is 32 bit) constitutes
a single bank. However, since older 30 pin simms were 8 bit, you needed
four of those to make a single bank. P5 has a 64 bit wide memory bus, so
you need a pair of 32 bit, 72 pin simms to make a bank. Because a dimm
(dual inline memory module) is effectively equal to a pair of simms
(single inline memory module), you only need a single dimm for P5 and
other systems with a 64 bit memory bus. My Alpha 164LX is jumper
selectable between 128 bit and 256 bit memory bus, so if I set the jumper
on 256, I'd need four equal dimms to make a single bank.
Although there are always weird niche cases, generally speaking you only
need identical modules (in terms of size, speed and type) when they're
used in a single bank. You generally don't need all banks to be
identical. Two examples: in my work computer I have a 128MB PC100 dimm
in bank 0 and a 256MB PC100 dimm in bank 1. In my Alphastation 200 at
home (which has a 64 bit memory bus), bank 0 is a pair of 32MB simms, and
bank 1 is a pair of 64MB simms.
Mike
-- Mike Tibor Univ. of Alaska Anchorage (907) 786-1001 voice Network Technician Consortium Library (907) 786-6050 fax tibor@lib.uaa.alaska.edu http://www.lib.uaa.alaska.edu/~tibor/ http://www.lib.uaa.alaska.edu/~tibor/pgpkey for PGP public key--------- To unsubscribe, send email to <aklug-request@aklug.org> with 'unsubscribe' in the message body.
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