johnl@ima.UUCP (08/11/83)
#R:ucbesvax:12800006:ima:13200002:000:911 ima!johnl Aug 10 09:34:00 1983 The BBN C/70 is a microprogrammable engine that is microprogrammed to interpret something close to Ritchie C compiler intermediate code. It does indeed have ten-bit bytes, which makes practically every program you try to port to it break. I helped them a little when they were trying to bring up uucp and it was bad news. It evolved from an internal project in which they tried reprogramming an existing C/30 and adding a little extra hardware to see how well it would run C. The C/30 is microprogrammed to simulate a DDP-316 (or is it 516, my ancient history is rusty) and is what BBN is using for Arpanet IMPs these days. My impression, from talking to some people who work there, is that they are no longer pushing the C/70 as a Unix engine but just as a supervisory node in private Arpanets. Compared to microprocessor- based systems, it's a little expensive for what you get. John Levine, ima!johnl
zrm@mit-eddie.UUCP (Zigurd R. Mednieks) (08/11/83)
The BBN C Machine is a re-microcoded IMP. The architechture had to be compatible with some nightmarish gizmo from the dark ages. On the other hand, if ten bit bytes don't ruin your day, being able to microcode C subroutine calls might be a win. I hope their lisp machine is nothing like their C machine. It is considerably more difficult to make an architechture run lisp reasonably than it is to run C. Though, if they use some og these spare bits for tagging locations by type (cdr, hidden pointer, etc.) they may be able to come up with something that has some advantage of a general pupose mini. They will have a hard time mactching the software environments of Lisp Machine Lisp and Interlisp-D, though. Cheers, Zig
bhyde@inmet.UUCP (08/11/83)
#R:ucbesvax:12800006:inmet:2500003:000:938 inmet!bhyde Aug 10 17:26:00 1983 Well, first there was the Arpanet and it was build using Honeywell Sue minicomputers. Then Honeywell went out of buisness making the Sue and the arpanet code got too big for 16bit addresses. Soo... a microprogramable computer was spawned that had 20bit bus capacity and it was set up to simulate the Sue. That machine is known as the MBB or microprogramable building block. It can be expanded to have special hardware to help with instruction decode and bus management and such. The C machines are just such an extention. The instruction set is sort of tunned to be what sounds good for C programs. The nice feature in the design is that the registers subprogramming calling instructions save and restore a few registers for you. The word size of the machine is 20bits, the bytes are 10bits, thus the 10bit characters, who cares? Except that the BBN lisp machine was built in the same building they share no common ground.
bcase@uiuccsb.UUCP (08/14/83)
#R:ucbesvax:12800006:uiuccsb:5600002:000:885
uiuccsb!bcase Aug 13 21:32:00 1983
To expand a bit: One of the best features of the BBN C machine is that
it has 1024 registers. Upon procedure call, a new bank of 8 are allocated
for the new procedure context (and of course they are deallocated upon
procedure return (er, make that function call and function return)).
This mechanism reduces greatly the overhead of calling functions. The
problem is that the contexts are isolated from their neighbors. By over-
lapping the contexts, procedures may pass parameters back and forth.
This overlapping idea is the big win of the Berkeley RISC chip.
As far as the BBN C machine instruction set goes, it is really nothing
great. With respect to the C programming language, some of the more
commonly occuring special cases are supported, but I wouldn't really
want to write a compiler for it.
Brian Case
University of Illinois (er, not any more: I graduated.)darrelj@sdcrdcf.UUCP (Darrel VanBuer) (08/14/83)
The BBN Lisp machine (known as Jerico) runs Interlisp. Because there was considerable cooperation among ISI, Xerox and BBN in porting Interlisp to new environments (VAX, Dolphin and Jerico) they share a great deal of old and new code (especially that which imitates the Tenex environment). I don't know what the windowing is like on the Jerico, but the majority of the environment on the Dolphin comes from vanilla Interlisp. Darrel J. Van Buer sdcrdcf!darrelj UUCP VanBuer@USC-ECL.ARPA