From owner-freebsd-hackers@freebsd.org Tue Sep 15 22:20:13 2015 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 0A9549CD1EB; Tue, 15 Sep 2015 22:20:13 +0000 (UTC) (envelope-from mozolevsky@gmail.com) Received: from mail-wi0-x22c.google.com (mail-wi0-x22c.google.com [IPv6:2a00:1450:400c:c05::22c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 98B5213B5; Tue, 15 Sep 2015 22:20:12 +0000 (UTC) (envelope-from mozolevsky@gmail.com) Received: by wiclk2 with SMTP id lk2so46421989wic.1; Tue, 15 Sep 2015 15:20:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc:content-type; bh=Ywu45W0TmIThbrBRdQGk+TLp855viyrKm19mvovyCvk=; b=T1nZhNfajaQoehw4UHAW9H+AHjHc9CjxEB+3AekyqMaRB+i00bJQzTOXcRjlduKjpB a7E+k64n186EdvsuhLdPK9bF1ywwVs58oj/Zl5/hJoGzbZwE6qw6Qp83+q34JWIAkRAs gHXt94y2LrD51EYUCUopvdx2IHCETm1Q0+8PkKid4Dm8QdtZexLQ0ZUPhMb0Nj3yq+ac Dm2mL7U30G4vWNpG3CwQPnztu8mcTln9IeS37Q7V+yMxs3nK3EucC/HF+Lr9qXslevX5 K0ORlNH48c9nJVy2euceCsiVzLo3m1DvIJykxCtE7CPVnvhmPNM+V15XMC6tBffOjaQu cgrA== X-Received: by 10.180.24.3 with SMTP id q3mr12248775wif.24.1442355610637; Tue, 15 Sep 2015 15:20:10 -0700 (PDT) MIME-Version: 1.0 Sender: mozolevsky@gmail.com Received: by 10.28.55.18 with HTTP; Tue, 15 Sep 2015 15:19:31 -0700 (PDT) In-Reply-To: <41EFCF21-D3B0-4EC4-8EAB-417CA33821FC@netgate.com> References: <41EFCF21-D3B0-4EC4-8EAB-417CA33821FC@netgate.com> From: Igor Mozolevsky Date: Tue, 15 Sep 2015 23:19:31 +0100 X-Google-Sender-Auth: cwYKB4BO_2rXOu8O0nVQDetnIpQ Message-ID: Subject: Re: ECC support To: Jim Thompson Cc: Dieter BSD , Hackers freeBSD , freebsd-hardware@freebsd.org Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Sep 2015 22:20:13 -0000 On 15 September 2015 at 22:52, Jim Thompson wrote: Errors are corrected "on-the-fly," corrected data is almost never placed > back in memory. If the same corrupt data is read again, the correction > process is repeated. Replacing the data in memory would require processing > overhead that could accumulate and significantly diminish system > performance. If the error occurred because of random events and isn't a > defect in the memory, the memory address will be cleaned of the error when > the data is overwritten with other data. > Just to correct a small oversight- most (if not all?) boards have an option to scrub ECC memory in the background so as to prevent single bit (recoverable) errors from turning into double bit (irrecoverable but detectable) errors ;-) -- Igor M.