Interrupts and Temporal Decoupling

I am just finishing off reading the chapters of the Processor and System-on-Chip Simulation book (where I was part of contributing a chapter), and just read through the chapter about the Tensilica instruction-set simulator (ISS) solutions written by Grant Martin, Nenad Nedeljkovic and David Heine. They have a slightly different architecture from most other ISS solutions, since that they have an inherently variable target in the configurable and extensible Tensilica cores. However, the more interesting part of the chapter was the discussion on system modeling beyond the core. In particular, how they deal with interrupts to the core in the context of a temporally decoupled simulation.

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Pipeline Performance Simulator Anno 1960

I have just found what almost has to be the first cycle-accurate computer simulator in history. According to the article “Stretch-ing is Great Exercise — It Gets You in Shape to Win” by Frederick Brooks (the man behind the Mythical Man-Month) in the January-March 2010 issue of IEEE Annals of the History of Computing, IBM created a simulator of the pipeline for the IBM 7030 “Stretch” computer developed from 1956 to 1961 (photo from

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Real-time control when cores become free

ImageA very interesting idea that has been bandied around for a while in manycore land is the notion that in the future, we will see a total inversion in today’s cost intuition for computers. Today, we are all versed in the idea that processor cores and processing times are quite precious, while memory is free. For best performance, you need to care about the cache system, but in the end, the goal is to keep those processor pipelines as busy as possible. Processors have traditionally been the most expensive part of a system, and ideas such as Integrated Modular Avionics are invented to make the best use of a resource perceived as rare and expensive…

But is that really always going to be true? Is it reasonably to think of CPU cores are being free but other resources as expensive? And what happens to program and system design then?

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