home *** CD-ROM | disk | FTP | other *** search
- Path: sparky!uunet!mcsun!uknet!gdt!aber!fronta.aber.ac.uk!pcg
- From: pcg@aber.ac.uk (Piercarlo Grandi)
- Newsgroups: comp.arch
- Subject: Re: IBM AS/400 is the world's slowest computer
- Message-ID: <PCG.92Dec27194335@decb.aber.ac.uk>
- Date: 27 Dec 92 19:43:35 GMT
- References: <Bzs3zn.43H.2@cs.cmu.edu> <1992Dec24.203452.22045@beaver.cs.washington.edu>
- <BzsIFK.EMF.2@cs.cmu.edu>
- <1992Dec25.033918.3246@beaver.cs.washington.edu>
- Sender: news@aber.ac.uk (USENET news service)
- Reply-To: pcg@aber.ac.uk (Piercarlo Grandi)
- Organization: Prifysgol Cymru, Aberystwyth
- Lines: 49
- In-Reply-To: kolding@cs.washington.edu's message of 25 Dec 92 03: 39:18 GMT
- Nntp-Posting-Host: decb.aber.ac.uk
-
- On 25 Dec 92 03:39:18 GMT, kolding@cs.washington.edu (Eric Koldinger) said:
-
- kolding> Last I checked (4 years ago), the AS/400 supported RPG III,
- kolding> COBOL (I think), Pascal, PL/I, and they were coming out with a
- kolding> C compiler.
-
- Actually it's going to be even more bizarre. IBM have stated that C is
- going to become their major app dev language on the AS/400 (and in
- general across the whole SAA base, which now includes DCE!), which fact
- is quite amazing; as a side note I don't think Pascal is in SAA, so
- probably it is not supported on AS/400; and I seem to remember that PL/1
- is not available yet, even if it is 'scheduled' as it is in SAA.
-
- kolding> You don't generally use the capabilities at the applications
- kolding> level, and the languages provide no real ability to manipulate
- kolding> capabilities
-
- Actually I think that C on the AS/400 just runs in a 16MB memory object
- like most other tradictional languages. In much the same way it was
- implemented on the Burroughs descriptor machines.
-
- kolding> (I've often wondered exactly what C ended up looking like on
- kolding> that machine, as pointers and ints are definitely not the same,
- kolding> and casting an int to a pointer makes no sense).
-
- The AS/400 is Not a VAX - I can see a nice Spencer article on that being
- written up when we will all have AS/400s on our desks :-).
-
- kolding> There's a fundamental difference between hardware and software
- kolding> capabilities. Software capabilities can be forged, however
- kolding> improbable. For example, Amoeba capabilities are just long
- kolding> integers (32, 64 bits?). You can forge one, but I wouldn't bet
- kolding> on it. Hardware capabilities are secure and cannot be forged.
-
- AS I have remarked in another article, there are two general styles of
- capability implementation, those that keep capabilities in a segment,
- and those that mingle them with use data. Either style may be
- implemented in sw or hw, and actually capability segments are quite
- popular even with hw solutions.
-
- With capability segments, as long as you have a suitable MMU, hw or sw
- does not matter; otherwise it does, because the hw solution is to tag
- each word of memory with a bit, the sw solution si to tag each
- capability with a random key (encrypted), which, as you say, might be
- guessed.
- --
- Piercarlo Grandi, Dept of CS, PC/UW@Aberystwyth <pcg@aber.ac.uk>
- E l'italiano cantava, cantava. E le sue disperate invocazioni giunsero
- alle orecchie del suo divino protettore, il dio della barzelletta
-