29 Dec
2016
29 Dec
'16
8:04 p.m.
From: Cory Heisterkamp
this is likely as close as I'll ever come to
having a first generation
machine
Dude, as far as I'm concerned, if it uses some sort of circulating memory for
main memory (either delay line or drum), it's pretty much first generation (of
course, it all depends on how one defines generations).
(Unlike the very similar - in size/cost/role - Bendix G-15, it doesn't have
the 'next instruction' field in each instruction, to optimize performance,
though...)
Interesting factoid about the Bendix G-15: it was designed with the help of
one of the ACE people (Harry Huskey), and is basically a re-packaged ACE with
drum instead of delay lines. There's an interesting article by Huskey himself
in "Alan Turing's ACE" (by Jack Copeland) which discusses the G-15.
From: William Degnan
I am being very careful not to call this "the
first personal computer"
Oh, I think a good case can be made. People often cite the LINC as the first,
but the G-15 and LGP-30 were similar in cost and intent, albeit a generation
(at least) older.
Noel
29 Dec
29 Dec
9:51 p.m.
On 12/29/2016 10:04 PM, Noel Chiappa wrote:
Ouch! That means it runs one instruction per revolution of
the drum? that would slow it to something like 30 IPS!
From: Cory
Heisterkamp
this is likely as close as I'll ever come to
having a first generation
machine
Dude, as far as I'm concerned, if it uses some sort of circulating memory for
main memory (either delay line or drum), it's pretty much first generation (of
course, it all depends on how one defines generations).
(Unlike the very similar - in size/cost/role - Bendix G-15, it doesn't have
the 'next instruction' field in each instruction, to optimize performance,
though...) Interesting factoid about the Bendix G-15: it was
designed with the help of
one of the ACE people (Harry Huskey), and is basically a re-packaged ACE with
drum instead of delay lines. There's an interesting article by Huskey himself
in "Alan Turing's ACE" (by Jack Copeland) which discusses the G-15.
SEVERAL generations older. Core memory was a HUGE advance.
Rather more complicated than a drum, but got rid of the
horrid latency with a drum. Even if you optimized the
executable code, machines like the G-15 had all sorts of
insane trickery to make data access faster. There were
instructions that would copy a whole long line of data to
the short lines so that these could be accessed every 4 word
times, instead of having to wait a full drum revolution for
the next word. There were all sorts of synchronization
issues between where the instruction word was and where a
data word was. (Not meaning it would cause a failure, but a
small program loop that was passing over a list of data
words in a long line would be slowed to one loop per every
few drum rotations, as the data access instruction would
hang waiting on the data word to come around, then have to
wait for the instruction word to come around, etc.)
Programming the G-15 was massively arcane, with all sorts of
side effects and especially tricks to improve performance,
so your program would run in a day, instead of a couple
WEEKS!!!!
Then, of course, The LINC was a discrete transistor machine,
ran off a plain 120 V outlet, didn't require air
conditioning beyond typical office environment, etc. And,
it had a CRT display that was used for OS interaction,
program editing and viewing data. That was also a big step up.
Jon
From: William Degnan
I am being very careful not to call this
"the first personal computer"
Oh, I think a good case can be made. People often cite the LINC as the first,
but the G-15 and LGP-30 were similar in cost and intent, albeit a generation
(at least) older.
11:09 p.m.
On Thu, Dec 29, 2016 at 11:51:27PM -0600, Jon Elson wrote:
There were instructions that would copy a whole long
line of data to
the short lines so that these could be accessed every 4 word times,
instead of having to wait a full drum revolution for the next word.
Yeah, I had forgotten about the short lines.
IIRC there are 109 words on a full drum track (I am going to hand-wave
about the metadata on the track because otherwise your brain would
explode.) So 29msec to watch the 109 words go around. Oh, did you
think that instructions only took one word-time to execute? hahahahahah.
No.
So you had to understand the period of time each instruction would run,
before you picked the address of the next instruction. So you optimize
for that for about the first, say, 80 instructions of the code on that track.
Good for you! But now ...
The rest of the instruction slots probably aren't going to be optimal. In
fact, Murphy being who he is, there are almost certainly pessimal.
So.
Now, do it again, _just slightly_ de-optimizing your layout of the first 80
and see if you can cram the rest in without wasting too many drum cycles.
Lather, rinse, repeat.
(as you might imagine, most coding was done in machine language -- the
compilers trying to deal with this was a nightmare. And waaaaaay slow.)
Programming the G-15 was massively arcane, with all
sorts of side effects
and especially tricks to improve performance, so your program would run
in a day, instead of a couple WEEKS!!!!
It was worse.
There were occasions where you wished to *pessimize* access.
Again, these are 50-year-old bits in my brain, but it may have had something
to do with waiting for the multiply and divide to finish up. Or perhaps it
was I/O. I was not doing enough heavy programming to encounter that.
After all, it was my first machine.
So easy to learn!
mcl
30 Dec
30 Dec
7:57 a.m.
On 12/30/2016 01:09 AM, Mark Linimon wrote:
(as you might imagine, most coding was done in machine
language -- the compilers trying to deal with this was a
nightmare. And waaaaaay slow.)
Yes, supposedly the Algol compiler took two days to
run on a
modest program.
Jon
9:49 a.m.
On Dec 30, 2016, at 12:51 AM, Jon Elson <elson at
pico-systems.com> wrote:
On 12/29/2016 10:04 PM, Noel Chiappa wrote:
The Dutch computer ARMAC had a nice optimization, a track buffer. Under software control
a given track would be copied to that buffer (in some sort of RAM -- core?) and then
references to those addresses would be satisfied from the buffer. You could think of that
as a very early cache. That was the machine on which Dijkstra first implemented the
spanning tree algorithm (as a demo program for an exhibition).
For first generation machines, you could distinguish between vacuum tube ones, and the
earlier relay machines.
I have an old set of lecture notes I'm translating, for a course on computer design
from 1948, which discusses various memory types. Not core memory, that came later. But
it mentions drums, and theorizes that those might be operated at 60,000 rpm... I'm
not sure where that optimism came from. Perhaps because the author was a mathematician
rather than a mechanical engineer?
paul
...
Ouch! That means it runs one
instruction per revolution of the drum? that would slow it to something like 30 IPS!
...
> Oh, I think a good case can be
made. People often cite the LINC as the first,
> but the G-15 and LGP-30 were similar in cost and intent, albeit a generation
> (at least) older.
>
SEVERAL generations older. Core memory was a HUGE advance. Rather more complicated than
a drum, but got rid of the horrid latency with a drum. Even if you optimized the
executable code, machines like the G-15 had all sorts of insane trickery to make data
access faster. There were instructions that would copy a whole long line of data to the
short lines so that these could be accessed every 4 word times, instead of having to wait
a full drum revolution for the next word. 
12:14 p.m.
On 12/30/2016 09:49 AM, Paul Koning wrote:
I have an old set of lecture notes I'm
translating, for a course on
computer design from 1948, which discusses various memory types. Not
core memory, that came later. But it mentions drums, and theorizes
that those might be operated at 60,000 rpm... I'm not sure where
that optimism came from. Perhaps because the author was a
mathematician rather than a mechanical engineer?
CDC ADL back in the late 1960s was testing a prototype high-speed drum
for the STAR--100K RPM in vacuo, ISTR. Probably a Jim
Thornton-inspired scheme. I do recall Neil Lincoln mentioning that the
observation window became coated with drum material in the first few
minutes.
The idea was a very fast paging store. That and the SCROLL tape/disk
device are two that come to mind.
Anent the LGP30--some drums were equipped with several heads spaced
around the same track to cut down on latency.
Logic need not be vacuum-tube or transistor--I recall the Univac Solid
State machines that used magnetic core as well as the Parametrons of NEC.
Drum machines persisted a bit longer than one would expect; e.g., the
Litton 1601 was produced in the early 70s.
A photo:
http://techno-science.ca/en/collection-research/collection-item.php?id=1982…
Technical reference manual:
http://bitsavers.informatik.uni-stuttgart.de/pdf/litton/Litton1600_Technica…
Bit serial architecture, of course. An odd bird, if there ever was one.
--Chuck
3:22 p.m.
On 30/12/16 17:49, Paul Koning wrote:
The Dutch computer ARMAC had a nice optimization, a
track buffer.
Under software control a given track would be copied to that buffer
(in some sort of RAM -- core?) and then references to those addresses
would be satisfied from the buffer. You could think of that as a very
early cache. That was the machine on which Dijkstra first implemented
the spanning tree algorithm (as a demo program for an exhibition).
Spanning tree? Really? Surely you mean Shortest Path First?
Antonio
--
Antonio Carlini
arcarlini at iee.org
31 Dec
31 Dec
9:26 a.m.
On Dec 30, 2016, at 6:22 PM, Antonio Carlini
<a.carlini at ntlworld.com> wrote:
On 30/12/16 17:49, Paul Koning wrote:
Sorry, brain lapse. Yes, that's what I intended to say.
paul
The Dutch computer ARMAC had a nice optimization,
a track buffer. Under software control a given track would be copied to that buffer (in
some sort of RAM -- core?) and then references to those addresses would be satisfied from
the buffer. You could think of that as a very early cache. That was the machine on which
Dijkstra first implemented the spanning tree algorithm (as a demo program for an
exhibition).
Spanning tree? Really? Surely you mean Shortest Path First?
2674
days inactive
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11 comments
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a.carlini＠ntlworld.com -
cclist＠sydex.com -
cctalk＠snarc.net -
cisin＠xenosoft.com -
elson＠pico-systems.com -
jnc＠mercury.lcs.mit.edu -
linimon＠lonesome.com -
paulkoning＠comcast.net