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12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

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Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#21

Post by tlb »

fractallyte wrote: post #2

Way back in 1985, a seminal 'Computer Recreations' column in Scientific American featured the Mandelbrot set: https://www.scientificamerican.com/media/inline/blog/File/De... (A K Dewdney's columns were always fantastic - a whole new world of wonder for early 'home computer' users!) After careful study, my brother coded it in assembly on a C64. We both had the idea to double the display resolution (from 320x200 to 640…

I wrote something similar in Apple ][+ Basic. It had a cool optimization: it would scan 16 points around the boundary of each 64x64 pixel block, and if they were all-black (in the set) or all-white, it would assume the rest of the block was the same and finish quickly. My dot-matrix printer had something like 2000 pixels of width and limited-only-by-patience height, so the printouts were amazingly detailed.

I wish I'd had similarly inclined peers at the time. We could have totally geeked out. But I was the only one I knew.

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#22

Post by fernly »

wglb wrote: post #11

Very nicely done article. However, I think the 029 keypunch didn't overlap the lifetime of the 1401, but I could be wrong. The other marvel of the day was the 1403 printer, which had a lifetime that went long beyond the 1401. It was a bit noisy, and the cover you see in the photos there did serve as a pretty good damper. However, when I did a co-op at IBM in Portland Oregon during my engineering studies, they had a 1…

You are correct about the 029. However in the 1401 machine room at CHM there is an 026 which was the correct keypunch for the era. OP could have used that but would have had to punch it manually -- not fun! The 029 used is, as noted in the article, relay-driven from a USB port, so he could just dump the working executable from the simulator.

Of course for full authenticity he SHOULD have manually punched the source deck on the 026, fed it into the 1401 for assembly using the 1402 reader, and had Autocoder in the 1401 punch the executable deck on the 1402.

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#23

Post by nitrogen »

GnarfGnarf wrote: post #9

I worked as a paid programmer on card systems in 1970. I'm not saying things were better then. Give me C++ and Python any day over Assembler. However, there was something magical about being able to step through your program one instruction at a time using a switch on the control panel, or being able to display and modify the memory with lights & toggle switches. It was like you were reaching right into the soul of t…

"patch the binary card decks"

Is this the origin of the word "patch" in CS usage? As in, literally patching paper? Or does it trace further back to patching clothing?

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#24

Post by CamperBob2 »

kens wrote: post #7
guru_meditation wrote: post #3

The footnotes in this article are fantastic. I used the inflation calculator [1] to convert 1960s prices to today's dollars: - Rental price: ~$20,000 / month - Purchase price: ~$1,000,000 (yes, a million dollars). So what you're looking at is what used to be a million dollar computer. You could buy a car for every month you pay to use this machine, so you better had really useful programming ideas or it's back to pen…

I'm glad someone reads my footnotes :-). About the rentals - most customers rented instead of buying. This had a huge effect on computer companies. Starting a competitor was extremely capital intensive since you had to build the computers up front and then you got revenue monthly, rather than from big sales. Rentals also made IBM conservative since they didn't want to introduce a new machine that would obsolete all t…

Just curious, what's the MTBF of those two machines at the museum? Hard to believe those those germanium transistors aren't all leaky as heck by now.

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#25

Post by Johnythree »

nitrogen wrote: post #23
GnarfGnarf wrote: post #9

I worked as a paid programmer on card systems in 1970. I'm not saying things were better then. Give me C++ and Python any day over Assembler. However, there was something magical about being able to step through your program one instruction at a time using a switch on the control panel, or being able to display and modify the memory with lights & toggle switches. It was like you were reaching right into the soul of t…

"patch the binary card decks" Is this the origin of the word "patch" in CS usage? As in, literally patching paper? Or does it trace further back to patching clothing?

No, I don't think so.

Originally you programmed by plugging "Patch Cords" into field of jacks.

So to edit a program, you would swap around a bunch of Patch cords.

The term "patch cord" comes from old Telephone switch boards.

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#26

Post by e12e »

GnarfGnarf wrote: post #9

I worked as a paid programmer on card systems in 1970. I'm not saying things were better then. Give me C++ and Python any day over Assembler. However, there was something magical about being able to step through your program one instruction at a time using a switch on the control panel, or being able to display and modify the memory with lights & toggle switches. It was like you were reaching right into the soul of t…

Reminds me of: http://www.columbia.edu/cu/computinghistory/fisk.pdf

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#27

Post by e12e »

fractallyte wrote: post #2

Way back in 1985, a seminal 'Computer Recreations' column in Scientific American featured the Mandelbrot set: https://www.scientificamerican.com/media/inline/blog/File/De... (A K Dewdney's columns were always fantastic - a whole new world of wonder for early 'home computer' users!) After careful study, my brother coded it in assembly on a C64. We both had the idea to double the display resolution (from 320x200 to 640…

I recall writing a mandelbrot program on my Casio (in the awful Casio basic) in the late 90s, after reading Ivar Peterson's "The Mathematical Tourist" (actually started with Sierpinski Gasket variations, as that is much easier, not to mention faster). I was wondering how he managed to do it in 12 minutes on such an old machine -- until I realized he only checked 24 iterations. I believe I started at a 100... and it took ~6 hours to run (more than the time from lunch until I got home, anyway...).

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#28

Post by fractallyte »

guru_meditation wrote: post #5
fractallyte wrote: post #2

Way back in 1985, a seminal 'Computer Recreations' column in Scientific American featured the Mandelbrot set: https://www.scientificamerican.com/media/inline/blog/File/De... (A K Dewdney's columns were always fantastic - a whole new world of wonder for early 'home computer' users!) After careful study, my brother coded it in assembly on a C64. We both had the idea to double the display resolution (from 320x200 to 640…

I loved AK Dewdney's columns. The Core War [1] columns influenced me profoundly. Would love to see the mandelbrot printout scans :) [1] http://www.koth.org/info/akdewdney/

OK, just off the scanner: http://imgur.com/gallery/8z7zP

Generated with a Commodore 64, output on an Epson RX80 dot matrix printer, circa 1986. All coding credit to my genius brother!

Re: 12-minute Mandelbrot: fractals on a 50 year old IBM 1401 mainframe

#29

Post by fractallyte »

mikeash wrote: post #16
fractallyte wrote: post #2

Way back in 1985, a seminal 'Computer Recreations' column in Scientific American featured the Mandelbrot set: https://www.scientificamerican.com/media/inline/blog/File/De... (A K Dewdney's columns were always fantastic - a whole new world of wonder for early 'home computer' users!) After careful study, my brother coded it in assembly on a C64. We both had the idea to double the display resolution (from 320x200 to 640…

Pix or it didn't happen. Sorry, what I mean to say is: if you happen to have those printouts somewhere convenient, I would love to see what a 1980s assembly language generated, dot matrix printed Mandelbrot set looks like.

See my post above! ;-)
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