From owner-freebsd-questions@freebsd.org Thu Jan 11 15:02:14 2018 Return-Path: Delivered-To: freebsd-questions@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 096A7E67EFB for ; Thu, 11 Jan 2018 15:02:14 +0000 (UTC) (envelope-from galtsev@kicp.uchicago.edu) Received: from cosmo.uchicago.edu (cosmo.uchicago.edu [128.135.20.71]) by mx1.freebsd.org (Postfix) with ESMTP id E185C7515C for ; Thu, 11 Jan 2018 15:02:13 +0000 (UTC) (envelope-from galtsev@kicp.uchicago.edu) Received: by cosmo.uchicago.edu (Postfix, from userid 48) id 56A2FCB8D12; Thu, 11 Jan 2018 09:02:07 -0600 (CST) Received: from 108.68.170.208 (SquirrelMail authenticated user valeri) by cosmo.uchicago.edu with HTTP; Thu, 11 Jan 2018 09:02:07 -0600 (CST) Message-ID: <50615.108.68.170.208.1515682927.squirrel@cosmo.uchicago.edu> In-Reply-To: <44wp0ofr1w.fsf@be-well.ilk.org> References: <44wp0ofr1w.fsf@be-well.ilk.org> Date: Thu, 11 Jan 2018 09:02:07 -0600 (CST) Subject: Re: OT: Max system physical memory From: "Valeri Galtsev" To: "Lowell Gilbert" Cc: "Aryeh Friedman" , "FreeBSD Mailing List" Reply-To: galtsev@kicp.uchicago.edu User-Agent: SquirrelMail/1.4.8-5.el5.centos.7 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 11 Jan 2018 15:02:14 -0000 On Thu, January 11, 2018 7:44 am, Lowell Gilbert wrote: > Aryeh Friedman writes: > >> My computer (HP Pavilion P7-1234, FreeBSD 11.1-RELEASE [amd64]) has 2 >> 240 >> pin DIMM (DDR3, PC3-10600) the manual says the max memory is 8 GB but I >> see >> some 16 GB packages (2x8GB). If I put one or two of these in will it >> see >> the extra memory? > > Probably not. > It is hit and miss. It is possible that specifications were written based on largest available modules at the moment of writing. If replacement modules are compatible with memory controller (i.e., say, the same PC3-10600), it is possible they will work. There still is the chance they will not work reliably, _IF_ there are some less trivial specs of memory controller are involved. Such may be: bus amplifiers may only handle up to this capacitive load before signals go out of specs. In general, larger RAM has larger numbers of address inputs connected to given lead, which may entail larger capacitive load. System board layout may have its impact here as well. Apart from that (and maybe some internal schematic specifics of memory controller), there is nothing fundamental about 8 GB RAM limit, so it may work. But chance is it will not. In any case, don't mix RAM modules with different specs (look at timing details like CL as well) on the same memory bus. I hope, this helps. Valeri ++++++++++++++++++++++++++++++++++++++++ Valeri Galtsev Sr System Administrator Department of Astronomy and Astrophysics Kavli Institute for Cosmological Physics University of Chicago Phone: 773-702-4247 ++++++++++++++++++++++++++++++++++++++++