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Article View: comp.sys.sequent
Article #117

Re: Sequent Machines, what are their strengths & weaknesses

#117
From: Lennart Augustsson
Date: Sat, 09 Sep 1989 02:59
53 lines
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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
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From: augustss@cs.chalmers.se (Lennart Augustsson)
Newsgroups: comp.sys.sequent
Subject: Re: Sequent Machines, what are their strengths & weaknesses
Message-ID: <3235@fnatte.cs.chalmers.se>
Date: 9 Sep 89 02:59:29 GMT
Organization: Dept. of CS, Chalmers, Sweden
Lines: 53