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.
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.
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.
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.
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.