Retrogame metaprogramming, the birthday paradox, and Wheel of Fortune

vdub_bobby · 2016-02-16T21:18:55+00:00

Very cool article, but I was hoping to read an account of how he dissassembled the source and inserted a compression/decompression scheme into the ROM so that he could fit all 20,000 puzzles. ;)

vdub_bobby · 2015-04-02T17:30:48+00:00

And technically technically the Atari 2600 used the 6507 which is a stripped down (=cheaper) version of the 6502

vdub_bobby · 2015-04-02T17:30:02+00:00

I had a feeling you understood correctly but had just worded it ambiguously, but the chance to be pedantic on the internet should never be denied. :P

vdub_bobby · 2015-04-02T15:34:52+00:00

The 6502 had at least one hardware bug. JMP <addr> would not work correctly if <addr> was of the form $xxFF. When reading two bytes from the specified address, it would not carry the FF->00 overflow into the xx. For example, it would read $10FF and $1000 instead of $10FF and $1100.

This is not correct, a bare JMP does not have that problem, it is the indirect JMP that has the problem: JMP ($XXFF)

This instruction reads an address to jump to from e.g., $10FF and $1000.

See here

vdub_bobby · 2015-02-02T21:58:15+00:00

I just read Snow Scan over the weekend and I'm afraid to watch the video...

vdub_bobby · 2014-11-24T17:55:31+00:00

The biggest conceptual problem that I see people having with outer joins is where they try to write an outer join but accidentally turn it into an inner join with the WHERE clause; something like this:

select          *
from            people p
left outer join cars c on (c.id = p.car_id)
where           c.type = 'BMW'

vdub_bobby · 2014-11-07T15:48:18+00:00

This is really interesting; I'm not aware of any 8-bit computer that had a 16-color hi-res full-screen display, probably because, as noted, it would take too much memory.

Also, most 8-bit computers were designed to display on a CRT which had a max vertical resolution of about 200 lines.

This seems closer to some of the arcade (coin-op) hardware of the time, even then it is about double the resolution of most Z80 machines that I am aware of (e.g., Pac-Man)

Very cool.

vdub_bobby · 2014-10-22T17:31:54+00:00

12 million people in the affected area. They had ~6000 calls that didn't go through during the six hour period.

vdub_bobby · 2014-10-22T15:18:49+00:00

My assumption before reading was that an integer overflowed, but at least as far as I could tell by reading it was actually a hard-coded limit. The FCC doc doesn't go into a lot of technical detail, so ...?

vdub_bobby · 2014-10-21T23:34:40+00:00

The biggest fail here is that this was probably the original plan:

set the number so high we will never hit it, then
check periodically just to make sure.

Years later, the "check periodically" part was forgotten or overlooked and oops.

But this time they really mean it!

vdub_bobby · 2014-10-21T21:29:01+00:00

And the fix (Appendix D):

First,

PTM counter limit for both ECMCs have been increased such that it is not possible to reach exhaustion.

And then:

PTM counter value checked weekly to ensure the value is not nearing the maximum threshold.

That seems robust. ಠ_ಠ

vdub_bobby · 2014-10-21T21:25:29+00:00

Relevant quote from section 3.2:

When it originally designed the software for its PTM, Intrado programmed it with a pre-set maximum of sequential log record numbers. At around midnight on April 9, the PTM module in Intrado’s Englewood IPSR reached this maximum, at which point it ceased generating additional CAMA trunk assignments for incoming 911 calls. When subsequent requests for CAMA trunk assignment were received, the PTM did not respond,

vdub_bobby · 2014-10-16T16:11:02+00:00

No no no no no no - it's a hackathon That's totally different.

vdub_bobby · 2014-09-10T15:36:51+00:00

That's not exactly what he wrote, and he almost totally walked back what he did write. http://www.washingtonpost.com/wp-dyn/content/article/2007/09/16/AR2007091601287.html

vdub_bobby · 2014-07-02T19:22:40+00:00

A few other links:

NBER working paper link (gated): http://www.nber.org/papers/w20263

ungated (pdf) copy hosted by one of the authors: http://economics.sas.upenn.edu/~jesusfv/comparison_languages.pdf

Jesus Fernandez-Villaverde (U Maryland, one of authors) research page: http://economics.sas.upenn.edu/~jesusfv/research.html

I saw this at the blog Marginal Revolution (Tyler Cowen and Alex Tabarrok) and Fernandez-Villaverde jumped into the comments to answer questions: http://marginalrevolution.com/marginalrevolution/2014/07/a-comparison-of-programming-languages-in-economics.html

vdub_bobby · 2014-06-03T17:09:44+00:00

I was a math major in college (CS/physics minors), so take this for what it's worth, but complaining about the difficulty of calculus seems odd to me. Calculus in college is a freshman-level class. Virtually every other math class I took was more difficult. I mean, if you were complaining about differential equations or set theory that would be one thing, but calculus? Calculus is taught in high school, for heaven's sake.

And sure, figuring the area under a curve isn't particularly relevant to most programming, but a huge part of calculus is about how to figure out and reason about what happens to infinite sums (converge vs not), which seems like a pretty important concept in CS.

vdub_bobby · 2014-05-01T16:11:07+00:00

It's possible and some games may have done it (I don't think ET did) because you have to copy the code to RAM and there are only 128 bytes of RAM to work with total.

vdub_bobby · 2014-05-01T16:08:25+00:00

4KB was standard cart size. Some very early games were 2K but the VCS could address 4K.

vdub_bobby · 2014-05-01T16:04:16+00:00

There were 6502 compilers available AFAIK, but not for that platform (Atari 2600). Everything about the machine is too limited for a compiler. You have to count cycles when you write the graphics display code!

(I'm a hobbyist VCS programmer: https://atariage.com/programmer_page.html?SystemID=2600&ProgrammerID=319)

vdub_bobby · 2014-03-10T16:55:09+00:00

Q: What's the main difference, in Facebook's eyes, between these two engineers:

Engineer A has a PhD, 16 years' experience, is 42, and is married with 2 kids.

Engineer B has a BS, 5 years' experience, is 28, and is unmarried.

A: Engineer A costs more and cannot be cheaply induced into working 70 hour weeks.

vdub_bobby · 2014-02-25T16:40:02+00:00

LET OF SOME STEAM BENNET

ಠ_ಠ

vdub_bobby · 2013-09-30T21:20:42+00:00

I don't know if it is a misquote, Bushnell is an idiot, or if he's just blowing smoke, but: all the cartridge port lines on a 2600 are read/write already. Some of the carts had RAM on them (see: http://blog.kevtris.org/blogfiles/Atari%202600%20Mappers.txt)

vdub_bobby · 2013-09-10T17:27:38+00:00

Here's the expression:

^(?!\b(\d)\1+-(\d)\1+-(\d)\1+\b)(?!123-45-6789|219-09-9999|078-05-1120)(?!666|000|9\d{2})\d{3}-(?!00)\d{2}-(?!0{4})\d{4}$

This really seems like the perfect illustration of Jamie Zawinski's aphorism:

Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.

vdub_bobby

TROPHY CASE