From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists.gentoo.org ([140.105.134.102] helo=robin.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1IiozT-0004CI-DF for garchives@archives.gentoo.org; Fri, 19 Oct 2007 10:22:04 +0000 Received: from robin.gentoo.org (localhost [127.0.0.1]) by robin.gentoo.org (8.14.1/8.14.0) with SMTP id l9JA8PL7016235; Fri, 19 Oct 2007 10:08:25 GMT Received: from ciao.gmane.org (main.gmane.org [80.91.229.2]) by robin.gentoo.org (8.14.1/8.14.0) with ESMTP id l9JA8OdV016217 for ; Fri, 19 Oct 2007 10:08:24 GMT Received: from list by ciao.gmane.org with local (Exim 4.43) id 1IiomB-0007PT-0h for gentoo-amd64@lists.gentoo.org; Fri, 19 Oct 2007 10:08:19 +0000 Received: from ip68-230-96-73.ph.ph.cox.net ([68.230.96.73]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 19 Oct 2007 10:08:18 +0000 Received: from 1i5t5.duncan by ip68-230-96-73.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 19 Oct 2007 10:08:18 +0000 X-Injected-Via-Gmane: http://gmane.org/ To: gentoo-amd64@lists.gentoo.org From: Duncan <1i5t5.duncan@cox.net> Subject: [gentoo-amd64] Re: 965 chipset and 2 DIMM slots will never give 4GB available? Is that correct? Date: Fri, 19 Oct 2007 10:08:14 +0000 (UTC) Message-ID: References: <299eu4-vih.ln1@poboxes.info> <200710181500.24885.volker.armin.hemmann@tu-clausthal.de> Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-amd64@gentoo.org Reply-to: gentoo-amd64@lists.gentoo.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: ip68-230-96-73.ph.ph.cox.net User-Agent: Pan/0.132 (Waxed in Black) Sender: news X-Archives-Salt: 40a6fedc-2a62-4ac1-9671-52b67cc88e92 X-Archives-Hash: 7dd84fb286ddfbde945c2dfae34bd626 Volker Armin Hemmann posted 200710181500.24885.volker.armin.hemmann@tu-clausthal.de, excerpted below, on Thu, 18 Oct 2007 15:00:24 +0200: > On Donnerstag, 18. Oktober 2007, Evert wrote: > >> I read their text again and noticed: 'OS will allocate 3~4GB memory >> address for onboard device'. >> Wouldn't that mean it's simply a (kernel)configuration issue...? > > no, it is a 'stupid bios' issue. The bios could put the pci/other device > memory space somewhere in the high terrabyte area, but instead it > chooses to put it at the end of the 4gb range, because of historical > reasons. This is correct. Here's a bit more detail. Many legacy PCI devices (and possibly some PCI-E devices, I don't know as my board is PCI-X, not yet PCI-E) and/or their drivers (mainly a problem with closed source drivers if the device and board handles 64-bit, AFAIK) are designed to run in a 32-bit address space only. As such, PCI device address space is normally located at the top of the 32-bit addressable memory area -- 3.5 to 4 GB. Naturally, if devices are using that address space, it's not available to be used by memory, so there's a "memory hole" at that location -- about a half GB just below the 4 GB boundary, thus under /normal/ circumstances, limiting actual usable/addressable memory to ~3.5 GB if one has 4 GB memory, or ~half a GB less than total memory if one has > 4 GB. There is, however, a BIOS workaround, depending on whether the mobo and BIOS installed support it or not. Basically what it does is move the memory otherwise covered by the "hole" up beyond 4 GB, so with 4 GB memory, you'll actually have usable memory addresses running to ~4.5 GB. (Or, some implementations move the entire GB, or even two gigs, so you may see addresses to 5 or even 6 gigs, but only have 4 gigs memory. Mine seems to move 2 gigs, so my 8 gigs memory appears as 10 gigs at POST.) If the BIOS supports this memory address move, you'll see one or two different options therein. Since I'm booted ATM I don't have immediate access to my BIOS to check and I don't remember exactly what they are, but I have two separate options here. IIRC one of them is something like "contiguous memory" vs. something else. The other one I don't remember at all ATM, only that I had it. I never was entirely clear at what the specific interaction between them was, but one definitely has to be set correctly to get the addressing working right, while the other... I'm not sure about. I just played with it and a kernel option or two until I got it working. However, the first thing is that your BIOS supports it at all. If it doesn't, you're simply SOL, unless you are lucky and they have a BIOS update adding the feature. Unfortunately, given the reply from the board's support people as you quoted, specifically that they didn't mention any such feature at all, it would appear their BIOS doesn't support it, and you are stuck with 3.5 GB. Of course, if they don't support Linux, they may not have known that it can take advantage of such an option given the chance, and may have given you the standard MSWormOS (or whatever) support answer, and their BIOS actually /does/ have the option. Note that I've read of advanced users flashing a BIOS with the features they want but designed for another board using the same base chipset. Of course, that's going to void your warrantee and could well end up bricking your board, but it's an option if you want to risk it. It's also possible to replace the BIOS chip itself, and to buy BIOS chips pre- flashed with various BIOS images, so if you decided to go that route, you could buy one flashed with some BIOS with that feature and see if it worked, without risking overwriting the supported BIOS on your current chip. Of course, that's well beyond anything I've tried, and in the general case, if you were advanced enough to work with that sort of thing, you'd probably know all this including the above about the PCI device memory hole already, so it's well beyond anything I'd recommend. However, the option is there if you are suitably determined, and have access to the appropriate resources (a friend that has the tools and knows what they are doing, or funds to purchase the service commercially, or such that the risk of bricking isn't a major worry). If you'd like the specific BIOS settings, I can reboot and look them up, but I'm not going to bother unless given the above, you think you might have the options, need to know more, and specifically request that info. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- gentoo-amd64@gentoo.org mailing list