Spectre and Meltdown: How Cache Works

The year so far has been filled with news of Spectre and Meltdown. These exploits take advantage of features like speculative execution, and memory access timing. What they have in common is the fact that all modern processors use cache to access memory faster. We’ve all heard of cache, but what exactly is it, and how does it allow our computers to run faster?

In the simplest terms, cache is a fast memory. Computers have two storage systems: primary storage (RAM) and secondary storage (Hard Disk, SSD). From the processor’s point of view, loading data or instructions from RAM is slow — the CPU has to wait and do nothing for 100 cycles or more while the data is loaded. Loading from disk is even slower; millions of cycles are wasted. Cache is a small amount of very fast memory which is used to hold commonly accessed data and instructions. This means the processor only has to wait for the cache to be loaded once. After that, the data is accessible with no waiting.

A common (though aging) analogy for cache uses books to represent data: If you needed a specific book to look up an important piece of information, you would first check the books on your desk (cache memory). If your book isn’t there, you’d then go to the books on your shelves (RAM). If that search turned up empty, you’d head over to the local library (Hard Drive) and check out the book. Once back home, you would keep the book on your desk for quick reference — not immediately return it to the library shelves. This is how cache reading works.

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Fail of the Week: Engine Flips Out

A few weeks ago an incredible video of an engine exploding started making the rounds on Facebook. This particular engine was thankfully in a dyno room, rather than sitting a couple of feet away from a driver on a track. We’ve all seen engine carnage videos before, but this one stands out. This diesel engine literally rips itself apart, with the top half of the engine flipping and landing on one side of the room while the bottom half sits still spinning on the dyno frame.

Building performance engines is part science, part engineering, and part hacking. While F1 racing teams have millions of dollars of test and measurement equipment at their disposal, smaller shops have to operate on a much lower budget. In this case, the company makes their modifications, then tests things out in the dyno room. Usually, the tests work out fine. Sometimes though, things end spectacularly, as you can see with this diesel engine.

The engine in question belongs to Firepunk diesel, a racing team. It started life as a 6.7 liter Cummins diesel: the same engine you can find in Dodge Ram pickup trucks. This little engine wasn’t content to chug around town, though. The Firepunk team builds performance engines — drag racing and tractor pulling performance in this case. Little more than the engine block itself was original on this engine. Let’s take a deeper look.

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Henrietta Lacks and Immortal Cell Lines

In early 1951, a woman named Henrietta Lacks visited the “colored ward” at Johns Hopkins hospital for a painful lump she found on her cervix. She was seen by Dr. Howard W. Jones, who indeed found a tumor growing on the surface of her cervix. He took a tissue sample, which confirmed Henrietta’s worst fears: She had cancer.

The treatment at the time was to irradiate the tumor with radium tubes placed in and around the cervix. The hope was that this would kill the cancerous cells while preserving the healthy tissue. Unbeknownst to Henrietta, a biopsy was taken during her radium procedure. Slivers of her tumor and of healthy cervix cells were cut away. The cancer cells were used as part of a research project. Then something amazing happened: the cancerous cells grew and continued to grow outside of her body.

As Henrietta herself lay dying, the HeLa immortal cell line was born. This cell line has been used in nearly every aspect of medical research since the polio vaccine. Millions owe their lives to it. Yet, Henrietta and her family never gave consent for any of this. Her family was not informed or compensated. In fact, until recently, they didn’t fully grasp exactly how Henrietta’s cells were being used.

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The Secret of Twinkling Christmas Lights

With the holidays over, many of us are braving the elements to take down all those holiday lights. LED lights have largely taken over the market, but in some places, you can still get classic incandescent bulbs. There are some effects that LEDs can’t quite mimic yet. One of those is the magic of “twinkling” light sets, which [Alec Watson] explains in a Technology Connections video. Everyone has seen bulbs that flash, and strings that dim. But the twinkle effect until recently has been hard to describe.

Typical flashing bulbs use a bimetallic strip. As the filament of the bulb heats up, the strip bends, opening the circuit. Then the strip cools and closes the circuit again. Twinkling lights do exactly the opposite. The bimetallic strip shorts the bulb out rather than open the circuit. Twinkling sets also use a lot of bimetallic strip bulbs – typically every fifth bulb has a strip. The result of the bulbs being shorted out is that all be the bulbs in set see a higher voltage. This makes the entire strip shimmer in time with the flashing. That’s where the twinkling magic comes from.

It occurs to us that the voltage on the strip would be a great source of random seeds. Sure, you’d have to replace bulbs now and again, but how many people can say they get their random numbers from a set of Christmas lights?

If you’re curious how incandescent Christmas lights can blow and not take out the whole strip, check out this article about anti-fuses.

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Why Sony’s Trinitron Tubes Were the Best

If you’re old enough to remember Cathode Ray Tube (CRT) Televisions, you probably remember that Sony sold the top products. Their Trinitron tubes always made the best TVs and Computer Monitors. [Alec Watson] dives into the history of the Sony Trinitron tube.

Sony Color TVs didn’t start with Trinitron — for several years, Sony sold Chromatron tubes. Chromatron tubes used individually charged wires placed just behind the phosphor screen. The tubes worked, but they were expensive and didn’t offer any advantage over common shadow mask tubes. It was clear the company had to innovate, and thanks to some creative engineering, the Trinitron was born.

Closeup of a Trinitron tube shows unbroken vertical stripes which led to a brighter picture.

All color TV’s shoot three electron guns at a phosphor screen. Typical color TVs use a shadow mask — a metal sheet with tiny holes cut out. The holes ensure that the electron guns hit only the red, green and blue dots of phosphor. Trinitrons use vertical bars of single phosphor color and a picket fence like aperture grille. The aperture grill blocks less of the electron beam than a shadow mask, which results in a much brighter image. Trinitrons also use a single electron gun, with three separate cathodes.

[Alec] is doing some amazing work describing early TV systems and retro consumer electronics over on his YouTube channel, Technology Connections. We’ve added him to our Must watch subscription list.

Interested in retro CRTs? Check out Dan’s article on cleaning up the fogged plastic safety screen on the front of many CRTs.

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How Hackerspaces Spend Money

Running a hackerspace is no easy task. One of the biggest issues is money — how to collect in dues and donations, managing it, and how to spend it. Everyone has different interests and would like to see the budget go to their favorite project or resource. Milwaukee Makerspace has come up with a novel way to handle this. Members pay $40 a month in dues. $35 of that goes into the general budget. The member themselves can pick where the last $5 goes.

Using the hackerspace’s software, members chose where their $5 goes each month. It can all be spent in one area or split up among different resources at the hackerspace. Members choose from many different interests like the 3D printing area, the laser lab, the forge, or specific projects like the power racing series. This results in a budget for each area which can be used for materials and parts. It also gives the hackerspace board of directors information on which resources people are interested in, and which they aren’t.

In the current budget, no one is supporting the anodizing area, but lots of people are supporting the laser lab. This is just the sort of information the board could use when planning. Perhaps they could store the anodizing tools and expand the laser lab. Click through to the link above and see how this year’s cash voting panned out.

Of course, all this only works if you have a hackerspace with plenty of active members. In Milwaukee’s case, they have about 300 members. Would this work for your hackerspace? Let us know down in the comments!

Toy R/C Car Upgrade to Hobby Grade Parts

[HobbyPartz] wanted his toy grade Radio Controlled (R/C) to drive a bit more like the real thing, so he upgraded it to hobby grade electronics.

If you didn’t know, there’s a pecking order in the R/C world. There are the toy grade cars which you can find at your local big box store, and the hobby grade cars, which grace the shelves of the local hobby shop. Toy cars often come with great looking shells – Corvettes, Lamborghinis, Porsches,  or even Ferraris. It often seems like the manufacturer spent all their money licensing and molding the shell though because the mechanics and electronics leave a lot to be desired. You could pull the body off and put it on a hobby grade R/C car, but that could get expensive. It also can be tricky to find a car with exactly the right width and wheelbase.

[HobbyPartz] had just this problem with a great looking Ferrari Enzo model that you can see in the video below the break. As expected, the pretty shell hid some really cheap electronics underneath. This is easily fixed by pulling and tossing everything electronic. The steering system was non-proportional — only full left or right turns. He removed the existing steering hardware and hot glued in a standard R/C servo. Once the servo is in position, it’s  easy to connect the linkages to the wheels themselves.

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