From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 26 Jan 2001 09:43:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 26 Jan 2001 09:43:45 -0500 Received: from zikova.cvut.cz ([147.32.235.100]:11021 "EHLO zikova.cvut.cz") by vger.kernel.org with ESMTP id ; Fri, 26 Jan 2001 09:43:31 -0500 From: "Petr Vandrovec" Organization: CC CTU Prague To: "Richard B. Johnson" Date: Fri, 26 Jan 2001 15:41:10 MET-1 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Re: Linux Post codes during runtime, possibly OT CC: Matthew Dharm , "H. Peter Anvin" , linux-kernel@vger.kernel.org X-mailer: Pegasus Mail v3.40 Message-ID: <13AEBF842896@vcnet.vc.cvut.cz> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 26 Jan 01 at 8:58, Richard B. Johnson wrote: > On Thu, 25 Jan 2001, H. Peter Anvin wrote: > > > You could use the DMA scratch register at 0x19. I'm sure Linux doesn't > > > "save" stuff there when setting up the DMA controller. > > > > I will change the port on my machines and run them for a week. I > don't have any DEC Rainbows or other such. Yes, I know Linux will > not run on a '286. > > Since 0x19 is a hardware register in a DMA controller, specifically > called a "scratch" register, it is unlikely to hurt anything. Note > that the BIOS saves stuff in CMOS. It never expects hardware registers > to survive a "warm boot". It even checks in CMOS to see if it should > preserve RAM. Unless there are chips which need DELAY between accesses to DMA controller ;-) And I'm sure there are such. Also, if DMA controller is integrated on board, outb is done in different speed than ISA forwarded cycle to postcode port. Just in case, on my VIA, 1e6 outb(0,0x80) tooks 2.07s, 1e6 outb(0,0x19) tooks 2.33s - so there is definitely difference - although in other direction than I expected. (What you can expect from this ....) Petr Vandrovec vandrove@vc.cvut.cz - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/