From owner-freebsd-hackers@FreeBSD.ORG  Mon Jan 29 16:15:33 2007
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Date: Mon, 29 Jan 2007 10:56:00 -0500
From: "David S. Madole" <david@madole.net>
To: 'freebsd-hackers' <freebsd-hackers@freebsd.org>
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Cc: 'LI Xin' <delphij@delphij.net>
Subject: RE: Reading SPD information?
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> From LI Xin Monday, January 29, 2007 10:49 AM
>=20
> Just curious: is there any way to read RAM's SPD information on a
> running system?

Yes, not only can you read them, on many systems you can write to them too.

There is an unfinished program here that decodes and displays data for SDRA=
Ms and has an example of reprogramming bytes:

http://madole.net/spd/spd.c

I used this to re-program some SDRAM after adding parity chips to them.

Note that there is a write-protect pin on the DIMMs that motherboards are s=
upposed to activate to prevent writing in a system (i.e. so that a virus do=
es not trash your DIMMs) but none of the systems I have tested on actually =
implement this.

It's fairly easy to find the specs of the SPD contents with Google -- sorry=
 I don't have a direct reference handy.

David