3 Apr
1998
3 Apr
'98
7:44 a.m.
<Was dectape an attempt to remedy some of these problems? My
<hazy recollection was that you could treat dectape in some ways as if
<it were a disk.
Dectape was an attempt to achive moderate amount of storage at low cost
with good reliability. It's stop, turnaround time was poor but the cost
was very low. It was preceeded by linktape which was very much similar.
<How much data can magtape hold? If magtape was a portable media,
varies with the size of the reel and the density it was recorded at.
<does that mean that the manufacturers agreed on the width of
<the tape, the density of recording, the method of recording bits,
<etc.?
To a point.
<I have an old 9 track tape from a computer course I took in 1980.
<For sentimental reasons I'd love to get a copy of its contents. Is
<this possible do you think?
Highly likely if you can find someone with a drive.
<Is 'merge sort' an example of an application that required three tape
<drives?
Thats a typical one. Sometimes 4 drives were used plus maybe a disk
system. Two for source material, one for intermediate results, one or
more for programs and the last for final results. Some machines were
very limited in the local memory they had so programs often were broken
into small modules and loaded (chained) as needed on the fly. Imagine
processing 500k of data in a 16k memory where a portion was also used
for program code.
Allison
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FWIW, I've used the latest (and not yet committed) version of the
Begemot emulator to run 2.11BSD for over a week. In that time, I
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. vi works as well as vi ever works.
Greg
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Reasonable assumption.
From Greg Lehey <grog(a)lemis.com> Fri Apr 3
16:41:11 1998
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Date: Fri, 3 Apr 1998 15:41:11 +0900
From: Greg Lehey <grog(a)lemis.com>
To: Tim Shoppa <shoppa(a)alph02.triumf.ca>, wkt(a)CS.ADFA.OZ.au
Cc: pete(a)dunnington.U-NET.com, edgee(a)cyberpass.net, pups(a)minnie.cs.adfa.oz.au
Subject: Re: Bug in Bob Supnik's Emulator!
References: <199803280050.LAA05410(a)henry.cs.adfa.oz.au>
<9804030000.AA00122(a)alph02.triumf.ca>
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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.
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? From "Steven M. Schultz"
<sms(a)moe.2bsd.com> Fri Apr 3 17:50:23 1998
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Date: Thu, 2 Apr 1998 23:50:23 -0800 (PST)
From: "Steven M. Schultz" <sms(a)moe.2bsd.com>
Message-Id: <199804030750.XAA10664(a)moe.2bsd.com>
To: grog(a)lemis.com, shoppa(a)alph02.triumf.ca, wkt(a)CS.ADFA.OZ.au
Subject: Re: Bug in Bob Supnik's Emulator!
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Greg -
FWIW, I've used the latest (and not yet
committed) version of the
Begemot emulator to run 2.11BSD for over a week. In that time, I
AH, a new and improved version? Great! SOmething to look forward to.
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.
It was a possibility - the only other thing which I've seen cause
similar problems was bad memory/cache. I presumed your memory
wasn't failing ;).
Programs suddenly dying for no apparent reason on otherwise healthy
"hardware" led me to suspect a problem with the emulator. The final
arbiter of course is a real PDP-11 :)
I take it then that the problems went away as mysteriously as they
arrived and that all is well with your system (no more assembler
or kernel recompile troubles)?
Not having any great need of an emulated PDP-11 I've not pursued
the (suspected) bug in Bob Supnik's emulator. Even on a PentiumPro
an emulated 11 is slower than a real 11/73 (and a lot slower than an
11/93 - which I should cease neglecting and stuff a SCSI card into
some day as I did with the 11/73).
Steven
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From Greg Lehey <grog(a)lemis.com> Fri Apr 3
18:26:21 1998
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Date: Fri, 3 Apr 1998 17:26:21 +0900
From: Greg Lehey <grog(a)lemis.com>
To: "Steven M. Schultz" <sms(a)moe.2bsd.com>, shoppa(a)alph02.triumf.ca,
wkt(a)CS.ADFA.OZ.au
Cc: pups(a)minnie.cs.adfa.oz.au
Subject: Re: Bug in Bob Supnik's Emulator!
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On Thu, 2 April 1998 at 23:50:23 -0800, Steven M. Schultz wrote:
Greg -
It's the one I've been using all along. I never used an older version.
FWIW, I've used the latest (and not yet
committed) version of the
Begemot emulator to run 2.11BSD for over a week. In that time, I
AH, a new and improved version? Great! SOmething to look forward to. 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.
It was a possibility - the only other thing which I've seen cause
similar problems was bad memory/cache. I presumed your memory
wasn't failing ;). Programs suddenly dying for no apparent reason on
otherwise healthy
"hardware" led me to suspect a problem with the emulator. The final
arbiter of course is a real PDP-11 :)
Sure, that makes sense. I did too, but I couldn't see anything obvious.
I take it then that the problems went away as
mysteriously as they
arrived and that all is well with your system (no more assembler
or kernel recompile troubles)?
Well, not quite. I finally got back to the real work I should have
been doing, and I haven't had time to look at it again since. But
they went into hiding when I tried to show them to Hartmut :-) I think
we still have a problem somewhere. BTW, Hartmut had already upgraded
to PL 40? before I tried to start, so I'm still not completely
convinced that it's not something I did wrong in upgrading.
Not having any great need of an emulated PDP-11
I've not pursued
the (suspected) bug in Bob Supnik's emulator. Even on a PentiumPro
an emulated 11 is slower than a real 11/73 (and a lot slower than an
11/93 - which I should cease neglecting and stuff a SCSI card into
some day as I did with the 11/73).
Interesting. I was running this on an AMD K6/233, which should be
slower than a PPro, and I had the impression it was faster. Does
anybody have some benchmarks?
Greg
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