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- Newsgroups: comp.arch
- Path: sparky!uunet!rde!ksmith!keith
- From: keith@ksmith.uucp (Keith Smith)
- Subject: Re: IBM AS/400 is the world's slowest computer
- Organization: Keith's Computer, Hope Mills, NC
- Date: Mon, 28 Dec 92 04:05:35 GMT
- Message-ID: <1992Dec28.040535.8064@ksmith.uucp>
- References: <1992Dec24.203452.22045@beaver.cs.washington.edu> <BzsIFK.EMF.2@cs.cmu.edu> <1992Dec25.033918.3246@beaver.cs.washington.edu>
- Lines: 93
-
- In article <1992Dec25.033918.3246@beaver.cs.washington.edu> kolding@cs.washington.edu (Eric Koldinger) writes:
- >In article <BzsIFK.EMF.2@cs.cmu.edu> lindsay+@cs.cmu.edu (Donald Lindsay) writes:
- >>I don't think that RPG programmers deal with capabilities, so, the
- >>stock microprocessor needs only a stock RPG.
- >
- >RPG doesn't use the capability features, but OS/400 certainly does. Don't
- >forget that a computer is more than just the applications that it runs. RPG
- >coulde easily be implemented on any machine out there, but you wouldn't call it
- >an AS/400. Just because I can run C on it, I don't call it a PDP-11, eh?
-
- Wanna talk feature-ite-is? Talk OS/400.
-
- >
- >>What other languages are of importance on the AS/400? What is the OS
- >>written in, and are capabilities actually explicit at the source
- >>level?
- >
- >Last I checked (4 years ago), the AS/400 supported RPG III, COBOL (I think),
- >Pascal, PL/I, and they were coming out with a C compiler. You don't generally
-
- BASIC, ADA, SQL (Of sorts).
-
- Third Party even a wider variety. Check Amalgamated Software of North
- America for their current list.
-
- >use the capabilities at the applications level, and the languages provide no
- >real ability to manipulate capabilities (I've often wondered exactly what C
- >ended up looking like on that machine, as pointers and ints are definitely not
- >the same, and casting an int to a pointer makes no sense).
-
- Weeeellll, Depending on what you were doing AS/400 'C' ranges from
- bizarre to really bizarre. What makes no sense is opening a stream.
- And reading and writing from the kb/screen is like no 'C' you've ever
- programmed before in your life. Sort of a cross between the RPG and
- 'C'. Screen at a time oriented.
-
- >>My experience with software-based capabilites has been positive, so
- >>it's not clear to me, offhand, that a stock RS/6000 is out of the
- >>question.
- >
- >There's a fundamental difference between hardware and software capabilities.
- >Software capabilities can be forged, however improbable. For example, Amoeba
- >capabilities are just long integers (32, 64 bits?). You can forge one, but I
- >wouldn't bet on it. Hardware capabilities are secure and cannot be forged. On
- >the AS/400 there is no way to turn an integer into a capability, even for the
- >OS (although certain layers of the "microcode" probably can). Software
- >capabilities also do not (efficiently) support the fine grained protection of
- >hardware capabilities. On an architecture like the AS/400, EVERY memory
- >reference is checked against a capability, and individual bytes can be
- >protected. Software capabilities are typically used to protect larger grained
- >objects, and are only checked when that object is "bound" to your protection
- >domain.
-
- This sounds likely, but I avoided going in that deep. I also have
- trouble seeing why it's neccessary, Especially when I keep in mind that
- the early releases of OS/400 (v.1 and v.2) crashed for us on a regular
- basis just to keep us on our toes. SCO seems to be more stable and
- provide a large portion of the functionality. There are some security
- features I'd like to see implemented that the AS/400 had, but the same
- functionality is by no means unobtainable in an *IX enviroment. In fact
- it would not require a whole lot more code IMHO.
-
- What do you mean every memory reference is check against a capability?
- What does this mean. I was under the assumption that the machine model
- of the AS/400 is that everything you scribble on or read from lies
- somewhere on the terabyte or so of address space in the machine. This
- seems really stupid to me. Basically then by hiding the hardware in an
- address you would *HAVE* to check the memory references for capability,
- where if you just treated devices differently from the start you can
- avoid this. In fact you avoid 2 layers, the one at the OS level where
- you translate the Device work into a memory reference, and then at the
- microcode level where it gets translated *BACK* to some device
- operation. This seemed really silly to me when an IBM SE was telling me
- how great it was a couple of years back. As for process access
- faulting and sharing this is available on INTEL CPU's today. So what
- advantage is all of this software layering to *ME* the small business
- consumer. What is *MY* end benifit from all this.
-
- >A stock RS/6000 could certainly run most (all?) AS/400 applications, probably
- >faster than an AS/400. It couldn't, however, (efficiently) support the AS/400
- >OS, or the full architectural specification.
-
- Then again, *WHY* would you WANT to carry all that excess baggage around?
-
- >
- >Someone from IBM Rochester might want to correct me if my memory is failing
- >here. Merry Christmas...
-
- Yea, please do. Straighten me out too!
- --
- Keith Smith uunet!ksmith!keith 5719 Archer Rd.
- Digital Designs BBS 1-919-423-4216 Hope Mills, NC 28348-2201
- Somewhere in the Styx of North Carolina ...
-