On 12/29/2016 10:04 PM, Noel Chiappa wrote:
     > 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...)
Ouch! That means it runs one instruction per revolution of the drum? that would slow it to something like 30 IPS!
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.

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

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