treval@runx.oz (Trevor Luker) (09/07/89)
Hi all, I am interested to know more about 386 based sequent boxes. 1) Do the sequent compilers produce truly parallel execution of a particular procedure. (Producing multi-threaded execution of loops etc.) or does the architecture simply allow multiple processes to run in parallel (A la NCR 850). 2) I believe they run under Dynix. Is this compatible with "real" (AT&T) unix. (5.3 / 5.4 etc) 3) Does the architecture "scale" correctly, ie does performance increase linearly with the number of processes added? 4) The machine that I have seen has 2 dual-processor 386 boards with each chip running at 16 MHz. Are there speed up (33MHz) options available? What about 486 boards? 5) What are your experiences with bug-fixes and customer-support? 6) Given a free choice, would you buy another one... Thanks, treval
johno@dduck.ctt.bellcore.com (John OBrien) (09/08/89)
Trevor, Some of your questions require a bit of detail. I'll make these as short as possible. We can follow-up if you like. In article <218@runxtsa.runx.oz> treval@runx.oz (Trevor Luker) writes: > I am interested to know more about 386 based sequent boxes. > > 1) Do the sequent compilers produce truly parallel execution > of a particular procedure. (Producing multi-threaded execution > of loops etc.) or does the architecture simply allow multiple > processes to run in parallel (A la NCR 850). A couple of answers here. The sequent architecture does automatic multiprocessing across the available processors. The scheduler works quite well. The "Parallel Processing" is not done automatically! The Sequent compiler allows you to use library calls to implement calls to the parallel processing routines. There are third party compilers that try to parallelize loops and such. But for anything of any complexity, it is up to the person writing the program to parallelize it. This is not too difficult once you get used to using the library calls. The effort needed to parallelize you rprogram is completely dependant on the complexity of your program. The library routines are quite easy to use. > > 2) I believe they run under Dynix. Is this compatible with "real" > (AT&T) unix. (5.3 / 5.4 etc) The parallel processing libraries are not available under the AT&T dynix (they soon will be). DYNIX is a dual universe OS, running both BSD and AT&T. The parallel processing libraries are available under the BSD universe. The AT&T universe has few inconsistencies with standard AT&T 5.2. However, all administration is BSD. > > 3) Does the architecture "scale" correctly, ie does performance > increase linearly with the number of processes added? My tests say YES!!! > > 4) The machine that I have seen has 2 dual-processor 386 boards > with each chip running at 16 MHz. Are there speed up (33MHz) > options available? What about 486 boards? I'm not aware of any clock speed-up options. I'm sure the 486 boards will be available sooner or later. But I don't have hard info. > > 5) What are your experiences with bug-fixes and customer-support? Very responsive! Bug fixes have been shipped promptly. CUstomer support is great (although, we had some trouble with the time difference between Oregon and the east coast (7 AM in NJ is 4 AM in Oregon and no one is awake.) > > 6) Given a free choice, would you buy another one... Absolutely!!!!!!!! > >Thanks, treval Your welcome. John O'B John J. O'Brien ISCP (Integrated SCP) ctt!johno or johno@ctt RRC 4B-307 699-8788
augustss@cs.chalmers.se (Lennart Augustsson) (09/09/89)
In article <17580@bellcore.bellcore.com> johno@dduck.UUCP (John OBrien) writes: >> >> 5) What are your experiences with bug-fixes and customer-support? > > Very responsive! Bug fixes have been shipped promptly. CUstomer > support is great (although, we had some trouble with the time > difference between Oregon and the east coast (7 AM in NJ is 4 AM > in Oregon and no one is awake.) On this point I have to disagree. I don't know if being far away from Oregon has something to do with it (the Sequent office that is nearest to Sweden is in Amsterdam, Netherlands). I have sent around 10 mailbugs to Sequent, ranging from very serious (at least for me) to just annoying. Out of this I have just gotton a response for one of them (I was quite serious bug for me, so I really begged them for a response). The response was that they admitted that what I complained about really was a bug! I have seen no bug fixes (come to think of it, one of the bugs reported about 1 1/2 years ago has been fixed now) to my problems, it has now been about more than a year since I reported them. If you want to know the problems you can read more below. >> >> 6) Given a free choice, would you buy another one... > > Absolutely!!!!!!!! I agree!!! Despite some problems it is one of the nicest machines I have ever used. -- Lennart Augustsson Description of two serious problems (Sequent, are you listening?): 1. The sigstack system call is supposed to tell the system that a different stack is supposed to be used whenever a signal occurs. Despite this a signal still thrashes two locations on the ordinary stack. This can be very dangerous if you are using the stack pointer in a non-standard way (which I am in a language implementation). The problem is present already in the original BSD 4.2 code, but has been fixed in 4.3. I have now fixed this bug myself (since Sequent seems to be incapable if doing it), by discompiling the sigstack system call and merging in the BSD 4.3 fixes and installing this as a new system call. Anyone who needs this fix badly, just drop me a mail and I'll send you the code (about 50 lines of C). 2. Under some very peculiar circumstances involving instructions with the LOCK prefix crossing page boundaries and causing page faults the program will get the Illegal instruction signal. There are work arounds to this, but they are messy. -- Lennart Augustsson Email: augustss@cs.chalmers.se or augustss@chalmers.csnet