Author: Jakob

Applications that can make use of more compute power (e.g., iPod Video)

A question that pops up quite often when computer architects and representatives from firms like Intel encounter a crowd today is but just what do you need more computing power for????. Most regular users are fairly happy with the speed at which they process words, surf the web, read email, do IP phone calls, crunch numbers in Excel, and other common tasks. It is hard to perceive the need for more speed in everyday tasks, unlike a decade or two ago when you could definitely ask for improvement. I remember scrolling a page in PageMaker on a Mac SE (8Mhz 68000). You counted the clicks and waited for the screen to jump, redraw, jump, redraw, stabilize… quite a different experience from working with modern computers and far more complex software that still responds instantaneously to almost any work.

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Handbook of Real-Time and Embedded Systems

Cover of Handbook of Embedded and Real-Time Systems The “Handbook of Real-Time and Embedded Systems” (ToC, Amazon, CRC Press) is now out. I and my university research colleague and friend Andreas Ermedahl have written a chapter on worst-case execution time analysis. We talk some about the theories and techniques, but we try to discuss practical experience in actual industrial use. Both static, dynamic, and hybrid techniques are covered.

I just got my personal copy, but my first impression of the book overall is very positive. The contents seems quite practical to a large extent, not as academic as one might have feared. Do check it out if you are into the field. It is not a collection of research paper, rather instructive chapters informed by solid research but with applications in mind.

Off-Topic: Video in the iPod Nano (Update, updated once)

A short update to the previous posting on how to compress video for the nano.

Black iPod NanoIt turns out that the “iPod video” profile of Nero Recode is half aimed at showing video from your iPod on external devices. That’s the only good reason for the “high” resolution. I typically got a video size of 15MB per minute with these settings, which quickly fills up even gigabytes of space.

Using the “iPod Video-AVC” profile instead is optimized for viewing on the Nano itself and not on some external device. The resolution is down to 320×200-240 depending on source aspect ratio. And the resulting files are only about 5MB per minute, much more manageable for carrying a large video library on an iPod. I cannot see any difference in the quality of the output…

Update (2007-September-23): The default iPod-AVC setting has some issue with rapid cross-fades between scenes. To get around this, I set the quality settings to “2-pass” and “highest quality” in the detailed settings you can make in the second screen before moving on to actually encode things. This created very nice looking video that had no problems handling even the previously broken fades.

The cost was even more compute time. I think the current settings takes some 5 to 10 hours per material hour to encode (on my Athlon XP 2700+, not exactly a screamer by current standards).

Off-Topic: Getting video onto an iPod Nano (3G/Video)

Black iPod NanoThis is not in my self-assigned range of topics, but I like when other people put up their helpful notes of how to accomplish some task that I am researching. Thus, I feel obliged to do the same when I have tested something reasonably new.

The task at hand here is “how to get video into an iPod Nano”.

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AMP vs Virtualization

It just dawned on me recently (and it sure must have been obvious to those working with configuring AMP — Assymtric Multiprocessing Systems) that in an AMP setup, the operating systems involved actually know about each other and have to account for the fact that they are sharing a single processor chip with other operating systems. So you cannot just take two single-core operating system images from an existing multiple-processor (local memory) solution and put them on a single chip and things just work. You do need to prepare the boot process and find a way to nicely share the common I/O devices, timers, accelerator engines and other resources on the chip. This is materially different from a virtualized setup.

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SICS Multicore Day 2007 – More on Programming

Some more thoughts on how to program multicore machines that did not make it into my original posting from last week. Some of this was discussed at the multicore day, and others I have been thinking about for some time now.

One of the best ways to handle any hard problem is to make it “somebody else’s problem“. In computer science this is also known as abstraction, and it is a very useful principle for designing more productive programming languages and environments. Basically, the idea I am after is to let a programmer focus on the problem at hand, leaving somebody else to fill in the details and map the problem solution onto the execution substrate.

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A logo from 1996 and simulation for archival purposes

Back in 1996, DVP celebrated its 15th anniversary. When looking through my digital and paper archive, I found this gem: DVP 15 årThe official badge and logo for the 1996 anniversary! We also produced some mouse pads with this logo on them, one of which I still use for my daily job. Pretty good quality I must say.

The picture shown here was saved as GIF for use on the web. But scarily enough, apart from a few more GIF files, I could not open or even understand the file type of most of the files from that time, only ten years ago. Our digital archives are not very robust — more on that below.

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SICS Multicore Day August 31

The SICS Multicore Day August 31 was a really great event! We had some fantastic speakers presenting the latest industry research view on multicores and how to program them. Marc Tremblay did the first presentation in Europe of Sun’s upcoming Rock processor. Tim Mattson from Intel tried hard to provoke the crowd, and Vijay Saraswat of IBM presented their X10 language. Erik Hagersten from Uppsala University provided a short scene-setting talk about how multicore is becoming the norm.

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Fastscale minimal virtual machines — beautiful simple idea

A company called Fastscale Technologies has a product that is simple in concept and yet very powerful. Instead of using complete installs of heavy operating systems like Linux or Windows to run applications on virtual machines, they offer tools that provide minimal operating system configurations that are tailored to the needs of a particular application. Since only that application is going to be run on the virtual machine, this is sufficient. According to press reports, this means that you can run several times more virtual machines on a given host, compared to default OS installs. And boot an order of a magnitude faster.

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The Simulation of the first Amiga Custom Chips (1983)

ArsTechnica is running a history of the Amiga, and in part 3, “The first prototype” they describe a really interesting “simulation” solution for the custom chips in the first Amiga. This is in 1982-83, and there are no VHDL or Verilog simulators, nor any other EDA tools as we know them today. Even if they were, the Amiga company would not have been able to afford them. So in order to test their design, the Amiga engineers built chip replicas using breadboards and discrete logic chips. All in all, 7200 chips and a very large numbers of wires. Quite fascinating stuff, and they did manage to interface the main 68000 CPU to the breadboards and get a fully functional if a bit slow simulation of a complete Amiga computer with all its unique custom chips.

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DVL & DVP 25 years

My dear old education program, DVL, later DVP, (which made us call it DV*) is celebrating its 25th anniversary with a large dinner at Norrlands Nation on October 6, 2007. The official site is www.dvp.nu/25. I really hope that I can make it, it would be great seeing all of the other alumni från datavetenskapliga linjen/programmet and see where they have ended up and what they are doing now.

They also emailed out a call for pictures from the history of DV*. I’ll look through my old collections of memorabilia and see what I can find. What a chance for a trip down memory lane. It’s been ten years since I graduated. Time flies.

Real-Time in Sweden (RTiS) 2007

RTiS 2007 just took place in Västerås, Sweden. It is a biannual event where Swedish real-time research (and that really means embedded in general these days) presents new results and summarizes results from the past two years. For someone who has worked in the field for ten years, it really feels like a gathering of friends and old acquaintances. And always some fresh new faces. Due to a scheduling conflict, I was only able to make it to day one of two.

I presented a short summary of a paper I and a colleague at Virtutech wrote last year together with Ericsson and TietoEnator, on the Simics-based simulator for the Ericsson CPP system (see the publications page for 2006 and soon for 2007). I also presented the Simics tool and demoed it in the demo session. Overall, nice to be talking to the mixed academic-industrial audience.

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