From owner-freebsd-current Wed Apr 28 10: 0:44 1999 Delivered-To: freebsd-current@freebsd.org Received: from bug.us.dell.com (bug.us.dell.com [143.166.12.35]) by hub.freebsd.org (Postfix) with ESMTP id A50201522A for ; Wed, 28 Apr 1999 10:00:32 -0700 (PDT) (envelope-from tony@dell.com) Received: from ant (ant.us.dell.com [143.166.12.34]) by bug.us.dell.com (8.8.8/8.8.8) with SMTP id LAA03046; Wed, 28 Apr 1999 11:58:07 -0500 (CDT) (envelope-from tony@dell.com) Message-Id: <3.0.6.32.19990428115805.03c08a50@bug.us.dell.com> X-Sender: tony@bug.us.dell.com X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.6 (32) Date: Wed, 28 Apr 1999 11:58:05 -0500 To: Nate Williams , Doug Rabson From: Tony Overfield Subject: RTC extmem - was: Re: suspend mode broken since one week ago Cc: Warner Losh , Nate Williams , Alex Zepeda , Peter Mutsaers , freebsd-current@FreeBSD.ORG In-Reply-To: <199904281414.IAA08646@mt.sri.com> References: <199904280422.WAA04592@harmony.village.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >>[regarding RTC vs. BIOS selection algorithm] >I don't think this is complete, because I think (don't know) that many >older BIOS's only reported up to 64M of memory, so if you had more than >64M in the box it didn't report it. The RTC extmem cannot "report" >64 MB either. In fact, the RTC extmem is unreliable for many >64 MB systems. The only time reading the RTC extmem was helpful was when the BIOS reported less than 64 MB and the RTC extmem "reported" more than the BIOS, but still less than or equal to 64 MB. The exception to this is the case where the BIOS is trying to hide something from the operating system, such as the ACPI tables. Again, using the BIOS value is the right choice. Reading the RTC extmem value is only useful for systems that meet all of these requirements: 1. They do not support either of the newer BIOS memory functions, int 0x15 - 0xe820 or 0xe801. 2. They have an int 0x15 - 0x8800 function that is artificially limited to a value below 64 MB. 3. They do not have a BIOS that is trying to hide something important from the operating system. The number of systems for which this happens is becoming vanishingly small, IMO. (Yes, I do know which ones they were.) Tony To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message