From owner-freebsd-hackers Sun Jun 25 16:40:24 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id QAA12496 for hackers-outgoing; Sun, 25 Jun 1995 16:40:24 -0700 Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.34]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id QAA12488 for ; Sun, 25 Jun 1995 16:40:19 -0700 Received: (from bde@localhost) by godzilla.zeta.org.au (8.6.9/8.6.9) id JAA10041; Mon, 26 Jun 1995 09:37:34 +1000 Date: Mon, 26 Jun 1995 09:37:34 +1000 From: Bruce Evans Message-Id: <199506252337.JAA10041@godzilla.zeta.org.au> To: terry@cs.weber.edu, wpaul@skynet.ctr.columbia.edu Subject: Re: 2.05R reboot hangs Cc: hackers@freebsd.org, rgrimes@gndrsh.aac.dev.com Sender: hackers-owner@freebsd.org Precedence: bulk >> I seem to recall reading somewhere that there's a BIOS routine that >> can be used for rebooting the system. Now, I know using BIOS calls is a >> ... >This is the keyboard reset line. That's the "BIOS" call. It's the >standard way rests are done (it's how DOS fdisk did it). XTs don't have a BIOS reset. Jumping to the reset vector is the only way for them. fdisk might try both, or something more clever depending on what it is running on. >The problem with the keyboard reset code is (apparently) that the >gate A20 has not been reenabled. Disabled? This seems likely. The linear reset address is not 0xF000:0xFFF0 or whatever I said before; it is actually %eip = 0x0000fff0 + base(%cs) = 0xffff0000 = 0xfffffff0 This has A20 and other high bits set, so it works properly iff the ROM is shadowed in high memory at all times. Does GateA20 control A21-31? Bruce