Tuesday, July 30, 2013

Ohm's Circle

There are four common variables in circuits.  P = Power, V = Voltage, I = Current, and R = Resistance.  Knowing any two of those you can find the other two.  To do this you must derive the right formula though.  I always remember that V = IR, and P = IV.  From that you can find these:
`V = IR = sqrt(PR) = P / I`
`P = VI = V^2 / R = I^2 R`
`I = P/V = V/R = sqrt(P / R)`
`R = V/I = V^2 / P = P/I^2`

I discovered something called Ohm's Circle which presents those formulas quite nicely.  However, I always just search for it and have never found a particularly well executed one.  Two of the top google image results have mistakes.  So, I decided to make my own version.  I derived the above formulas by hand to double check it was all correct.

Friday, July 26, 2013

8 horrible courtroom jokes and their ensuing legal calamities

Defending Texas’s abortion restrictions before the Supreme Court, attorney Mr. Jay Floyd decided to open oral argument with a sexist joke. Arguing against two female attorneys, Floyd begins: “It’s an old joke, but when a man argues against two beautiful ladies like this, they are going to have the last word.” The joke is demeaning and (as Floyd himself admits) unoriginal, but it also lacks the saving grace of at least being funny. A recording of the oral argument, which can be listened to here, demonstrates just how badly the joke bombed with the Supreme Court. Painful silence endures for just over three seconds.

Bear Party

Saturday, July 20, 2013

The story behind football's innovative yellow first down line

While the line looks simple on TV, the technology behind it is very complex. Sensors were placed on the three main game cameras (at midfield and the two 20 yard lines), capturing the pan, tilt and zoom movements of those cameras 30 times a second. A three-dimensional, virtual model of each field had to be constructed, with the exact measurements of the crown of the field (the center of the field is always higher, for drainage, than the sides and ends, but the precise levels vary in each venue). An exhaustive color palette had to be produced on the fly as the game progressed, so that the green pixels of grass the yellow line replaced would be exactly the "right greens" even as shadows crossed the field and changed the grass hues -- an essential feature to assure replacing only the green blades of grass and not the green threads of a Packers or Eagles jersey.

Wednesday, July 17, 2013

Overriding BIOS limited CPU speed while running on battery

The Wrath of Dell

As it turns out, my work at salvaging a power adapter for my Dell Inspiron 6000 was not as much of a smashing success as I had initially thought.  I noticed that the battery charging tray indicator wasn't going away.  This happened sometimes, and required me to unplug the cord a few times.  However, I had duct taped the cord in place to prevent it from falling out, and didn't care to fix it.

Eventually I noticed that the power level was only going down.  I also noticed that I had suddenly lost the ability to watch .mp4, or just about any video over 480p.  The internet seemed even slower than usual, and I started noticing my cronjobs running even with their low nice levels.

I had a suspicion, but didn't want to look into it for fear of confirmation.  I eventually caved and discovered my battery was not charging.  The BIOS listed the AC adapter as an unknown device, and thus refused to charge.

I deduced that when I shorted the unknown-at-the-time third wire to the +19.5V wire I must have fried the chip on the motherboard that looked for other Dell products.

Further research confirmed my deepest fear: In addition to refusing to charge the battery, Dell forced the laptop to run at half speed if it didn't detect a Dell adapter.  I could certainly live with the battery not charging, as my laptop had long ago become a desktop, but an 800 MHz CPU was pushing it.

The Search for a Fix

I began looking for a hacked BIOS to undo all the Dell nonsense with renewed gusto.  Unfortunately, while it seemed possible, it didn't seem anyone had published anything.  I briefly considered hacking the BIOS myself, as my previous BIOS messing withs have gone well.

Eventually, I discovered that while the battery charging was controlled by the BIOS, the CPU speed was controlled by the OS, with the BIOS only able to suggest speeds.

I learned of CPU governors which were profiles that controlled the speed.  By running the command cpufreq-info I found my current governor was ondemand, and I had the common performance governor available.  I could update the governor with:
sudo echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

I confirmed this with cpufreq-info, but it also showed my speed still at 800MHz.  The policy said that the speed had to be between 800MHz and 800MHz and that the governor could decide which speed to use between those limits.  This made me suspect that perhaps the BIOS had more control over the speed than I had hoped.  Still, I persevered as it seemed other Dell users had fixed this, although they were being coy about exactly how.

The Voyage to 1.6 GHz

The breakthrough came from this site and its comments, which revealed there was a seperate BIOS limit that I was missing.

For me, the key file was at: /sys/devices/system/cpu/cpu0/cpufreq/bios_limit  You can edit this file similar to the above command, but I recommend opening it with a text editor to see its current setting.  For me, it was at 800000, and needed to be changed to 1600000, evidently in KHz.

This is all well and good, but it will be overwritten by the BIOS on each boot.  To prevent that you can edit your GRUB file at: /etc/default/grub to contain this magic line: GRUB_CMDLINE_LINUX="processor.ignore_ppc=1"  Follow that by running update-grub to, as the name implies, update grub, and reboot.

Now, cpufreq-info revealed that the policy could pick speeds from 800MHz to 1.6GHz, and what's more it was picking 1.6GHz.  I left the governor at ondemand since it was successfully raising the speed as needed.

On a page full of technical Linux commands I found the most recent comment good:
"You all sound mega tech savvy so this might be a stupid answer but i fixed mine by blowing down the end of the cable….."

Friday, July 5, 2013

Why the McWrap Is So Important to McDonald's

After lengthy discussions with produce suppliers around the country, Coudreaut managed to add one new ingredient to the McDonald’s arsenal: the English cucumber. That might not seem like a big change, but when the chain added sliced apples to its menu, it immediately became one of the largest buyers of apples in the country. The company had to build up reserves of edamame before it introduced its Asian salad. Coudreaut would like to add guacamole one day. Who knows what that would do to the avocado supply?

For cucumbers, McDonald’s went to Taylor Farms and Fresh Express, a producer and distributor owned by Chiquita. Then it had to figure out how the vegetable could be sliced, evenly, before it reached the restaurants. The chain expects to use about 6 million pounds this year. McDonald’s also tested the size of the chicken breast and the amount of lettuce. Initially, the sandwich was made with a half-breast of chicken and loads of produce. “We talked a lot about the veggies,” says Leslie Truelove, director of marketing in the U.S. “But we went too far. People thought it was a salad.” People wanted more meat. Now the wrap has a full breast of chicken, a handful of shredded lettuce, 10 leaves of spring mix, two cucumber slices, and two tomato slices—no more, no less.