Interview Frenzy 2

This post has been sitting in my draft folder for a very long time, I forgot about it, but here it is –

Third round of job searching. I didn’t get nearly as many interviews as I had hoped, probably due to sloppy resume, and I’m also a lot more selective this time, applying only to hardware positions (too much software for me, need to take a break… life is about balance!). I did get some really cool interviews, though.

nVidia (System Engineer, post-silicon verification)

Very intense interview! An entire hour of quizzing, on everything from C++ to analog circuits (filter transfer function). Most of them are fairly standard, though, and programming part is easy (I guess they don’t really expect electrical engineers to know how to program). I can’t believe I actually programmed in C++ and VHDL over the phone.

  • How to construct a NOR gate using 1 input multiplexers? (LUT, cascaded muxes)
  • How to construct a D flip flop with async reset from regular DFF (I’m still not sure. Mux on output and input?)
  • Merge 2 files containing lists of words, remove duplicates, sort, and output to third file (binary search tree, pre-order traversal)
  • Given a series RC circuit, determine response at DC and 1MHz (1 pole transfer function)
  • 100 students took an exam. mean score = 500, SD = 100. Highest 15% pass. Is 650 pass? (basic stats)
  • With a 3L cup, a 5L cup, and infinite supply of water, measure 4L (classical interview question. somewhat hard. did a depth-first search in my head)

nVidia second interview

This one is all on digital logic, still fairly difficult. Talked in detail about the PCB I made for robotics lab, and firmware programming.

  • How to construct a D-latch using transmission gates and inverters (digital feedback, bus contention)
  • What is the delay of the latch (add up delays of signal path)
  • How to construct a D-flipflop using 2 D-latches (in series, one gets inverted clock)
  • What are the parameters (setup time, clock-to-Q) of the D-FF (delay of first latch, and delay of second latch)
  • 2 D-FF with combinational logic between them. What is the timing constraint given delay of the logic circuit, setup time, clock-to-Q, clock delay to second FF, and clock jitter (clock jitter is the hard part, 2tj must be added because in worst case, 2 clock edges can be T/2 + 2tj apart)

Nuvation (firmware developer)

Mostly talked about projects I have done.

  • on a microcontroller, when is it appropriate to use interrupts, when is it not? (responsiveness, external stimuli, easy to introduce bugs if interrupt handler shares data with main loop, etc)
  • how to test software (whitebox, blackbox, edge cases, typical cases, etc, big words, pretend to be a software engineer)

Nuvation second interview

Again mostly projects I have done, and some project management stuff. How I organize the electrical team at Thunderbots, etc.

  • how to implement brushless motor controller in FPGA and MCU (probably because I mentioned brushless motors in my resume)
  • some simple questions about PCB design that I don’t remember. Something about vias and component packages…

Sifteo (Electrical engineer)

Mostly talked about my involvement with Thunderbots, and PCB design experiences, and what is it like to work at Sifteo. They make very cool stuff!

  • how to bring up and test a new circuit (different approaches, top-down, bottom-up, etc)

I really liked the Sifteo position, but I ended up choosing NVIDIA because it’s my first work term in the US, and working for a big company simplifies things (visa, housing, etc). And California!!!

10,000 Hours Rule (Outliers: The Story of Success)

“Ten thousand hours of practice is required to achieve the level of mastery associated with being a world-class expert – in anything … composers, basketball players, fiction writers, ice skaters, concert pianists, chess players, master criminals” – Malcolm Gladwell, Outliers: The Story of Success.

Very inspirational book, highly recommended.

The author observed that, no one can become a world-class master in anything, without putting in about 10,000 hours of practice, in any field, and perhaps more importantly, no one can NOT become a world-class master, after putting in 10,000 hours of practice.

Geniuses don’t exist. They are merely a combination of opportunity and 10,000 hours of practice. They are self-fulfilling prophecies.

Makes sense if you think about it – you randomly pick a kid, tell him he has great potential to become the greatest hockey player ever, and put him through 10 years of 10 hours practice a day. In the end, you will get the greatest hockey player ever. Your prediction was correct.

Bill Gates was a high school kid at a time where only universities had computers. He went to a high school for rich people, with rich parents that decided to buy them a computer (opportunity). He programmed day and night for 10 years. 10,000 hours later, he became a world class programmer (at that time).

Mozart famously started composing at six, but he did not produce masterpieces until he was 20, by which time he has accumulated about 10,000 hours of practice.

Bobby Fischer, famous ex-World Chess Champion, also spent about 10 years of intense practice before becoming a grandmaster.

All NHL players were born in the right months, arbitrarily selected by their birthday when they were 8-9 years old (*), and put through about 10 years of intense practice.

There is no field in which anyone can become a world-class expert with less practice, or not become one with more practice.

Do I believe it? I don’t know. I’ll give it a try and let you know.

* NHL, and most other professional sport leagues, select players by their birthday. Funny? I thought so, too. And it’s true.

If you look at the birthday of NHL players, there are overwhelming number of players born in Jan, Feb, and March. Very few in the later months, October, November, December. Is it because people born in earlier months are more talented? Of course not.

To become a NHL player, one must be selected at an age of 8-9, in a tryout, for junior league. They don’t want to miss any “talent”, so it has to be done at a young age. Everyone are at the same age. That sounds fair? It does, until you realize that, people who are born on December 31 need to compete with people born on January 1, almost a whole year older. At an age of 8-9, kids grow A LOT in a year’s time. 9 year olds are much bigger and more coordinated than 8 year olds. Then the selected ones go through much more intense training, and self-fulfills their prophecy of being the most talented ones.

Someone reportedly went to talk to NHL about this. They agree. And they said they are not going to fix it because it’s “too complicated” to have to hold different tryouts for different month groups. They rather lose about half the talent.

So if you ever want your kids to become a NHL player, try to conceive in March, to give birth in January. If you accidentally give birth too early in December, might as well just tell him to pick up a new hobby. Painting or something, since he probably won’t get into any professional sport, because most of them also have January cutoff.

RIP Steve Jobs

(This post is not pre-written, hence the few hours delay)

RIP Steve Jobs.

As an engineer, I am a big fan of ingenuity, and Steve has done a lot of that in his life.

I will not bore you with a list of things he did, since you probably have read that a thousand times from different places already, and the list is way too long.

I have a lot of respect for people that are original, and are willing to take risks to move the world forward. Steve is a man that deserves recognition.

Aside – I have always been an anti-fan of Apple for it’s shady business practices, and that has not changed. Only a job offer from Apple would change that. If I ever stop badmouthing Apple, that’s probably what happened. This is a completely different issue.

Now I am really curious about what will happen to Apple after their source of innovation is gone. iSheep will still be iSheep, but I’m sure there are also Apple fans that will leave once Apple becomes just any other tech company. I do not believe anyone can bring Apple back to the former golden Steve-era (early to mid 2000s, when Apple changed the world in so many ways). With the releases of recent Apple products, it’s not hard to notice that Steve’s absence/illness has already stopped innovation.

Can another person like Steve come out to push the tech world forward?