Notes on Memory Consistency and Cache Coherence

June 27th, 2008 admin

Here are some of my notes on the topic of memory consistency and cache coherence, and how uniprocessor and multiprocessor cores have to be built to support the consistency models. Most of this was written up when I was preparing for my Qualifying Exam at NC State University last semester. This is a relatively complicated topic to understand well, and there might still be several mistakes in how I understood the ideas. Also, this might only make sense, and be interesting, to people familiar with these areas of computer architecture. Here’s the pdf file: Notes on Memory Consistency and Cache Coherence

Posted in Information, Tutorials | No Comments »

Protect your platinum – catalytic converter theft

June 25th, 2008 admin

Someone neatly sawed off and removed the catalytic converter from under Kavita’s Pontiac Vibe yesterday while it was parked in the Friday Center park-n-ride lot in the UNC, Chapel Hill, campus. When Kavita started up the car, it started up with a loud, complaining roar rather than the usual hum. Clueless about why the car was so loud, she stopped the car and started to look under the hood to see if she could spot any obvious problem, when someone shouted from across the lot, “Looks like your catalytic converter was stolen as well.” He was another of the many victims of such theft yesterday. He called campus police, which was good because Kavita was not sure what she should do next. She tried reaching me, but I was in the gym, away from my cell phone. So she called Anant in California, got my gym’s number and had the lady at the front desk in the gym call for me over the PA system. I came home from the gym, got Kavita added as an associate on my AAA account and ordered a tow-truck to get the car to our mechanic at Wasp Automotive. Meanwhile, the campus police officer, a lady, stayed with Kavita until I reached there. This was nice of her. With typical wait times of 60 minutes for the region, we were expecting a long wait at the lot for the tow truck. However, he showed up a few minutes after I reached the Friday center in my car. He noticed that Kavita’s license plate had expired and the tow-truck guy could not, therefore, tow the car as part of AAA’s services. He was a nice guy though. He had a huge lump of tobacco pushed against the inside of his left cheek wall, and in between spitting, he informed us that in the very same lot, last Wednesday, there were nearly 40 cases of the exact same incident. He had himself towed many a cat-less car that day. He said, “If you want me to tow this to Wasp, I can do it, but you can save yourself a hundreded and twenty five dollars by just driving it yourself. It will be loud, but fine.” He wanted us to file a complaint with the campus police since they had not provided any protection to the lot in spite of the sudden spate of these thefts since last week. We thanked him showing up at such short notice, and for not charging us a penny for his time and effort. His trip must have cost him at least a few bucks of gas. He did inform us that the state will slap a $250 fine on us because of the expired license plate. I drove the car with the emergency blinkers on to Wasp and left it there with a note that the insurance people want to take a look at it before we start off any repairs. So with the $250 fine, the insurance deductible (assuming they pay for it), this misadventure will cost us upwards of a thousand dollars. With our trip to India planned for this Sunday, I am not even sure if the repairs/insurance claims etc will be done before we leave.

In any case, the point of this whole entry is that catalytic converters are a relatively easy part of your car to steal. They contain precious metals like platinum, palladium etc. and when mined for the metals can fetch $50 to $100. Replacing them, of course, costs more than a thousand dollars usually. There is nothing you can do to avoid such theft except avoiding parking in desolate lots. When parking in public areas make sure you park at a location that is visible to pedestrian or vehicular traffic. Such visibility maybe a deterrent. Park close to mall entrances if malls do not have police cars driving around the lot or surveillance cameras. Comprehensive insurance is a good idea, as long as the deductible is low enough that you don’t end up paying the whole amount. Park inside a garage where possible. If you have any other ideas about how to reduce the chances of such theft, let me know.

Posted in Experiences | 2 Comments »

Niagara Falls, Niagara Uplifts

June 7th, 2008 admin

Last weekend, Kavita and I visited our friends, Vishal and Nimisha in Rochester, New York state. We met Vishal’s father too, who is currently visiting them. The highlight of the trip was the trip to Niagara Falls, an hour and a half’s drive away from Rochester. Niagara Falls consist of three main falls – The American Falls, the Bridal Veil Falls and the gigantic, Horseshoe Falls -and these three can be seen in this order in this picture from Wikipedia’s article about Niagara. Comprehending the immensity of this behemoth is hard once you are in the waters below engulfed by The Horseshoe Falls on three sides, especially if it is raining hard at the same time, as it was for us. There was only one escape with the rain pelting from above, swelling waters below, and the unstoppable din from the freefalling 50-meter walls of milky whiteness closing in on three sides – turn around and head to safety. And, thankfully, that is what the boat we were on, eventually, did.

Here are some pictures from the trip.

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