3 Apr
1998
3 Apr
'98
2:11 p.m.
On Apr 3, 15:41, Greg Lehey wrote:
Subject: Re: Bug in Bob Supnik's Emulator!
On Thu, 2 April 1998 at 16:00:40 -0800, Tim Shoppa wrote:
>> I suspect the FP emulation in Bob's Emulator, so it might be worth
>> watching the floating point values in the program. Bob mailed me during
>> the week, and I sent him a virgin binary of factor so he could verify that
>> there is a bug.
I'd be very surprised if factor used FP. My 7th Edition system's offline ATM,
so I can't check the source.
> More evidence of a bug is that 'vi'
doesn't work right under Bob
> Supnik's emulator, either. At one point Steven Schultz made some
> private speculations to me about where the problem might be, but
> I've forgotten the details. Is it possible that these two bugs
> are both due to FP emulation? Does the 2.11BSD 'vi' even use
> the FP registers?
Dunno, but I'd be surprised.
applied multiple patches to the system. I did have
some as yet
unexplained problems with the assembler, which Steven Schultz
considers to be due to the emulator (more specifically, instruction
restart), but Hartmut Brandt (the principal author) thinks this is
unlikely.
Well, it is one of the areas that causes trouble on different flavours of
PDP-11. Both DEC and Unix O/S's had all sorts of games being played in the
trap recovery code, according to which processor the O/S thought it was running
under. But AFAIK, that code only gets called if an instruction is aborted,
which I wouldn't expect would happen exactly the same way every time factor was
run (but again, I'm speculating without having looked at the code).
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
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