From owner-freebsd-alpha Fri Oct 9 18:52:04 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id SAA14183 for freebsd-alpha-outgoing; Fri, 9 Oct 1998 18:52:04 -0700 (PDT) (envelope-from owner-freebsd-alpha@FreeBSD.ORG) Received: from lestat.nas.nasa.gov (lestat.nas.nasa.gov [129.99.50.29]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id SAA14148 for ; Fri, 9 Oct 1998 18:51:39 -0700 (PDT) (envelope-from thorpej@lestat.nas.nasa.gov) Received: from localhost (localhost [127.0.0.1]) by lestat.nas.nasa.gov (8.8.8/8.6.12) with SMTP id SAA07944; Fri, 9 Oct 1998 18:51:09 -0700 (PDT) Message-Id: <199810100151.SAA07944@lestat.nas.nasa.gov> X-Authentication-Warning: lestat.nas.nasa.gov: localhost [127.0.0.1] didn't use HELO protocol To: David Seifert Cc: alpha@FreeBSD.ORG Subject: Re: PALcode Reply-To: Jason Thorpe From: Jason Thorpe Date: Fri, 09 Oct 1998 18:51:08 -0700 Sender: owner-freebsd-alpha@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Fri, 09 Oct 98 16:25:44 PDT David Seifert wrote: > The PALcode customises the machine for a particular OS. > That is the whole point of the PALcode. > There is PALcode for Unix, PALcode for VMS, and PALcode for NT. > > Similar deal with the console software. > SRM for VMS and Unix, ARC or AlphaBIOS for NT. > > ARC cannot read a BSD disklabel. Right, basically, the NT PALcode is just totally alien, as far as UNIX is concerned: - Interrupt semantics are different. - VM semantics are different (makes the Alpha a lot like a combination of MIPS and x86... "funny that!" ... including limitation to 32-bit address space, user and KSEGs, 2-level page table traversal a'la x86, etc.) - All the traps are different. - The process (i.e. HWPCB) structures are different. What it comes down to is this: "An Alpha with NT PALcode is a different processor architecture." The instruction set may be the same, but basically everything you have to deal with at the low-level in an operating system is different. Side-note: it's somewhat amusing/scary how non-x86-centric NT actually is at the bootstrap level... For example, on the x86 and on the PowerPC, NT requires a glue layer on top of the native console software on that platform (i.e. PC BIOS or OpenFirmware) that emulates the old MIPS ARC console... I have no doubt that deep in the guts of the x86 HAL, there is code that emulates e.g. the MIPS KSEG by direct-mapping the memory in the system probably by using the large-page support in modern x86 CPUs. Jason R. Thorpe thorpej@nas.nasa.gov NASA Ames Research Center Home: +1 408 866 1912 NAS: M/S 258-5 Work: +1 650 604 0935 Moffett Field, CA 94035 Pager: +1 650 940 5942 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message