From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 14 May 2001 21:45:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 14 May 2001 21:45:38 -0400 Received: from femail19.sdc1.sfba.home.com ([24.0.95.128]:37536 "EHLO femail19.sdc1.sfba.home.com") by vger.kernel.org with ESMTP id ; Mon, 14 May 2001 21:45:32 -0400 Message-ID: <3B008D00.A201D690@didntduck.org> Date: Mon, 14 May 2001 21:57:20 -0400 From: Brian Gerst X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.4.0-test11 i586) X-Accept-Language: en MIME-Version: 1.0 To: "H. Peter Anvin" CC: linux-kernel@vger.kernel.org Subject: Re: 2.4.4 kernel reports wrong amount of physical memory In-Reply-To: <200105142250.f4EMoHt02203@adsl-209-76-109-63.dsl.snfc21.pacbell.net> <9dpt1e$185$1@cesium.transmeta.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "H. Peter Anvin" wrote: > > Followup to: > By author: Rik van Riel > In newsgroup: linux.dev.kernel > > > > On Mon, 14 May 2001, Wayne Whitney wrote: > > > In mailing-lists.linux-kernel, you wrote: > > > > > > > You need to compile highmem support into the kernel if you want to > > > > use more than 890 MB of RAM, set it to maximum 4GB for best > > > > performance... > > > > > > On a similar note, what is the maximum physical memory supported > > > by the 4GB option? > > > > Ummm, 4GB maybe? ;) > > > > It seems obvious once you know why the limits are there. The 1 GB > limit (actually 1024-128 MB = 896 MB) is a software limit; the 4 GB > and 64 GB limits are hardware limits and are exact. Even with the 4GB and 64GB options, some physical address space has to be reserved for memory mapped I/O. -- Brian Gerst