Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!necntc!ima!johnl From: johnl@ima.ISC.COM (John R. Levine) Newsgroups: comp.arch Subject: Re: C machine Message-ID: <776@ima.ISC.COM> Date: Tue, 8-Dec-87 17:07:21 EST Article-I.D.: ima.776 Posted: Tue Dec 8 17:07:21 1987 Date-Received: Sun, 13-Dec-87 14:29:24 EST References: <759@auscso.UUCP> <1061@winchester.UUCP> <6203@jade.BERKELEY.EDU> Reply-To: johnl@ima.UUCP (John R. Levine) Distribution: na Organization: Not enough to make any difference Lines: 41 Keywords: C, Lilith (sp?), In Progress? Summary: BBN C/70 C machine In article <6203@jade.BERKELEY.EDU> jkh@violet.berkeley.edu (Jordan K. Hubbard) writes: >I think BBN developed a series of machines a few years back that >were supposedly optimized for C. ... The BBN C/70 was an interesting historical freak that really should never have escaped from the lab. They had a microprogrammable engine originally designed to emulate the DDP 516's used in Arpanet IMPs. That configuration, the C/30, has sold reasonably well. As an experiment, somebody wrote a set of microcode to implement something close to the reverse polish intermediate language of one of the Unix C compilers, brought up Unix on the box, and the C machine was born. On the way, they noticed that the 16 bit address space was inadequate for a modern Unix system, so they stretched it, much the same way that Boeing or Douglas stretches an airframe, so it ended up with a 20 bit address space and ten-bit bytes, making it the world's first fully metric-compatible computer. The original machine was the C/70, and my understanding was that the C/60 was the same machine in a smaller configuration. As you might imagine, the 99% of Unix software that assumes that bytes are eight bits broke in funny ways when confronted with ten-bit bytes, but they did get 7th edition Unix running reasonably well and used it extensively for network control on the Arpanet and the many private packet-switched nets that BBN has sold. They tried with minimal success to sell it as a general Unix engine, but it failed there for many reasons: -- programs broke on ten bit bytes -- twenty-bit addresses aren't bit enough -- heavily microcoded architecture caused lousy performance -- it wasn't designed for volume production, so it was expensive to build and so to sell -- nonstandard I/O interfaces meant that there weren't a lot of peripherals available. I suppose the lesson here is that when you try to turn a horse into a zebra, you end up with a camel. -- John R. Levine, IECC, PO Box 349, Cambridge MA 02238-0349, +1 617 492 3869 { ihnp4 | decvax | cbosgd | harvard | yale }!ima!johnl, Levine@YALE.something The Iran-Contra affair: None of this would have happened if Ronald Reagan were still alive.