I've been hearing this question a lot lately, and when I do, it reminds me how much I don't know. Here are some questions this question brings to mind. How does a keyboard work? Why can’t you press an arbitrary combination of three keys at once, except on fancy gaming keyboards? That implies somethi...

Most real-world problems are big enough that you can't just head for the end goal, you have to break them down into smaller parts and set up intermediate goals. For that matter, most games are that way too. “Win” is too big a goal in chess, so you might have a subgoal like don't get forked. While cr...

There's an ongoing debate over whether "AI" will ever be good enough to displace humans and, if so, when it will happen. In this debate, the optimists tend to focus on how much AI is improving and the pessimists point to all the ways AI isn't as good as an ideal human being. I think this misses two ...

It's generally accepted that any piece of software could be compromised with a backdoor. Prominent examples include the Sony/BMG installer, which had a backdoor built-in to allow Sony to keep users from copying the CD, which also allowed malicious third-parties to take over any machine with the soft...

Does it make sense for me to run ads on my blog? I've been thinking about this lately, since Carbon Ads contacted me about putting an ad up. What are the pros and cons? This isn't a rhetorical question. I'm genuinely interested in what you think. Pros Money Hey, who couldn't use more money? And it's...

This is a response to the following question from David Albert: My mental model of CPUs is stuck in the 1980s: basically boxes that do arithmetic, logic, bit twiddling and shifting, and loading and storing things in memory. I'm vaguely aware of various newer developments like vector instructions (SI...

Here's a language that gives near-C performance that feels like Python or Ruby with optional type annotations (that you can feed to one of two static analysis tools) that has good support for macros plus decent-ish support for FP, plus a lot more. What's not to like? I'm mostly not going to talk abo...

How much overhead should we expect from enabling integer overflow checks? Using a compiler flag or built-in intrinsics, we should be able to do the check with a conditional branch that branches based on the overflow flag that add and sub set. Code that looks like add %esi, %edi should turn into some...

Let's write a malloc and see how it works with existing programs! This is basically an expanded explanation of what I did after reading this tutorial by Marwan Burelle and then sitting down and trying to write my own implementation, so the steps are going to be fairly similar. The main implementatio...

Public discussions of discrimination in tech often result in someone claiming that discrimination is impossible because of market forces. Here's a quote from Marc Andreessen that sums up a common view1. Let's launch right into it. I think the critique that Silicon Valley companies are deliberately, ...

I was curious what different people worked on in Linux, so I tried grabbing data from the current git repository to see if I could pull that out of commit message data. This doesn't include history from before they switched to git, so it only goes back to 2005, but that's still a decent chunk of his...

If I had to guess, I'd say I probably work around hundreds of bugs in an average week, and thousands in a bad week. It's not unusual for me to run into a hundred new bugs in a single week. But I often get skepticism when I mention that I run into multiple new (to me) bugs per day, and that this is i...

I've seen all these studies that show how a 100ms improvement in page load time has a significant effect on page views, conversion rate, etc., but I'd never actually tried to optimize my site. This blog is a static Octopress site, hosted on GitHub Pages. Static sites are supposed to be fast, and Git...

I've noticed that builds are broken and tests fail a lot more often on open source projects than on “work” projects. I wasn't sure how much of that was my perception vs. reality, so I grabbed the Travis CI data for a few popular categories on GitHub1. For reference, at every place I've worked, two 9...

There are some pretty strong statements about types floating around out there. The claims range from the oft-repeated phrase that when you get the types to line up, everything just works, to “not relying on type safety is unethical (if you have an SLA)”1, "It boils down to cost vs benefit, actual st...

The latest version of the Intel manual has a couple of new instructions for non-volatile storage, like SSDs. What's that about? Before we look at the instructions in detail, let's take a look at the issues that exist with super fast NVRAM. One problem is that next generation storage technologies (PC...

Once upon a time, my computer architecture professor mentioned that using a random eviction policy for caches really isn't so bad. That random eviction isn't bad can be surprising — if your cache fills up and you have to get rid of something, choosing the least recently used (LRU) is an obvious choi...

This is an off-the-cuff comment for Hacker School's Paper of the Week Read Along series for Out of the Tar Pit. I find the idea itself, which is presented in sections 7-10, at the end of the paper, pretty interesting. However, I have some objections to the motivation for the idea, which makes up the...

Every once in a while, I hear how intrinsics have improved enough that it's safe to use them for high performance code. That would be nice. The promise of intrinsics is that you can write optimized code by calling out to functions (intrinsics) that correspond to particular assembly instructions. Sin...

UNITED STATES DISTRICT COURT NORTHERN DISTRICT OF CALIFORNIA SAN JOSE DIVISION IN RE: HIGH-TECH EMPLOYEE ANTITRUST LITIGATION THIS DOCUMENT RELATES TO: ALL ACTIONS Case No.: 11-CV-02509-LHK ORDER DENYING PLAINTIFFS' MOTION FOR PRELIMINARY APPROVAL OF SETTLEMENTS WITH ADOBE, APPLE, GOOGLE, AND INTEL ...

This is an archived USENET post from John Cooley on a competitive comparison between VHDL and Verilog that was done in 1997. I knew I hit a nerve. Usually when I publish a candid review of a particular conference or EDA product I typically see around 85 replies in my e-mail "in" box. Buried in my re...

I can't remember the last time I went a whole day without running into a software bug. For weeks, I couldn't invite anyone to Facebook events due to a bug that caused the invite button to not display on the invite screen. Google Maps has been giving me illegal and sometimes impossible directions eve...

Editing binaries is a trick that comes in handy a few times a year. You don't often need to, but when you do, there's no alternative. When I mention patching binaries, I get one of two reactions: complete shock or no reaction at all. As far as I can tell, this is because most people have one of thes...

Last week, Quartz published an article titled “There is no gender gap in tech salaries”. That resulted in linkbait copycat posts all over the internet, from obscure livejournals to Smithsonian.com. The claims are awfully strong, considering that the main study cited only looked at people who graduat...

In 1983, at the University of Wisconsin, Dina Bitton, David DeWitt, and Carolyn Turbyfill created a database benchmarking framework. Some of their results included (lower is better): Join without indices table {border-collapse:collapse;margin:0px auto;}table,th,td {border: 1px solid black;}td {text-...

In the fall of 2000, I took my first engineering class: ECE 352, an entry-level digital design class for first-year computer engineers. It was standing room only, filled with waitlisted students who would find seats later in the semester as people dropped out. We had been warned in orientation that ...

Dear David, I'm afraid my off the cuff response the other day wasn't too well thought out; when you talked about taking calc III and linear algebra, and getting resistance from one of your friends because "wolfram alpha can do all of that now," my first reaction was horror-- which is why I replied t...

Here's the graph of a toy benchmark1 of page-aligned vs. mis-aligned accesses; it shows a ratio of performance between the two at different working set sizes. If this benchmark seems contrived, it actually comes from a real world example of the disastrous performance implications of using nice power...

Earlier this year, I interviewed with a well-known tech startup, one of the hundreds of companies that claims to have harder interviews, more challenging work, and smarter employees than Google1. My first interviewer, John, gave me the standard tour: micro-kitchen stocked with a combination of healt...

In CPU design, most successful teams have a fairly long lineage and rely heavily on experienced engineers. When we look at CPU startups, teams that have a successful exist often have a core team that's been together for decades. For example, PA Semi's acquisition by Apple was a moderately successful...