Simulating Computer Architecture with “Mechanistic” Models – No more 100k Slowdown?

I have been working with computer simulation and computer architecture for more than 20 years, and one thing that has been remarkably stable over time is the simulation slowdown inherent in “cycle accurate” computer simulation. Regardless of who I talked to or what they were modeling, the simulators ran at around 100 thousand times slower than the machine being modeled. It even holds true going back to the 1960s! However, there is a variant of simulation that aims to make useful performance predictions while running around 10x faster (or more) – mechanistic models (in particular, the Sniper simulator).

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Additional Notes on Spotify

After about a month of using Spotify, it is time for an update. I got several people asking about how I was doing with Spotify, based on my previous blog post about the service. The results so far have honestly surprised me – it has become my default way of listening to music, despite all of my previous criticisms being pretty much validated. I guess the “access any song” is really a compelling value proposition, strong enough to overcome the limited organizational tools.

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The Benefit of Live Teachers (Applied to Myself)

I have been spending quite a bit of time in recent years developing training materials and doing trainings for Simics. There is always a discussion on how best to do training, in particular between live sessions with actual trainers and offline video and other self-study resources. I am a firm believer in the value of live training, and during our recent winter vacation up in the Swedish mountains I made myself provide a perfect example of the value of a teacher. I took a skiing lesson.

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I Finally Gave up and Tried Spotify

I am probably among the last people to have tried Spotify. When the service first arrived ten years ago I looked at it and concluded it seemed a poor match for my needs. To me, music is something you buy and own permanently in the style of old-fashioned CDs. The whole idea of a streaming service where an artist, album, or song could go missing all of sudden due to factors beyond your control just seemed (and still seems) suspicious. Everybody else seemed to love it, but that does not necessarily mean it is good…  However, I finally did jump in and try Spotify, and here is what I found.

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Intel Blog Post: Simulating Caches 10x Faster with Simics

Earlier this year, Arianna Delsante defended her Master’s Thesis in computer science at Uppsala University. Her thesis topic was to speed up cache and branch prediction simulation in Simics, and in the end she got a speed up of about 10x compared to previous implementations in Simics. I explain a bit more about cache simulation in fast functional simulators and what she did in my latest Intel Developer Zone Blog post, “Speeding-Up Cache Simulation in Simics by 10x“.

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“Studying the Advancement in Debugging Practice” / 2016 Paper

I find debugging a very interesting topic of study, so when I stumbled on the paper “Studying the advancement in debugging practice of professional software developers”, I had to do a blog on its contents.

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Cancer Part 2: Going Radioactive

As I chronicled earlier this year (see “A Sudden Case of Cancer”), I got a Thyroid Cancer diagnosis back in May of this year. In June I went through surgery which went very well. After only three weeks, I was sufficiently recovered to travel to Greece and give a keynote presentation at the SAMOS conference. My scar prevented me from taking as much as advantage as I could have of the sun and pool, but it was possible to do at least a little bit of bathing towards the end. Now, I have reached part two of the treatment, radioiodine therapy to knock out any lingering cancer cells. Basically, I am going radioactive for a few days.

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Failing to See WiFi Login Page [Captive Portal] / Solved

I have had some annoying problems in recent months with my work laptop refusing to connect to certain WiFi login pages (more technically known as Captive Portals), essentially locking me out of the WiFi in certain places. Here is how I solved it.

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More on Programming

My blog post from last week, “Programming for Everyone, Everyone’s a Programmer?,” gave rise to some good comments from friends and colleagues on the matter of programming. Some of the points are worth addressing in a continuation of the discussion.  To get the starting point, please read the previous post first.

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Programming for Everyone, Everyone’s a Programmer?

Recently, I have read some articles and seen product announcements based on the idea that we need to make programming easier. Making it easier is supposed to make more people program, and the underlying assumption is that programming can be easy enough that everyone can do it. I have also talked computer science undergraduate students who kind of asked me just how many years at the university you should do, and what do you actually in practice gain from a university degree in computer science? When I think about it, these two discussions really come down to the same question: Should everyone be a programmer? Can everyone be a programmer? What does it mean to be a programmer? How do you best learn to program?

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Intel Blog: A Mountain and Threading for Simics 6

A new short blog post on my Intel Developer Zone blog talks about the improved threading simulation core we have added in Simics version 6… and about how a colleague of mine climbed to the top of the highest mountain in Europe and showed a flag with our new Simics icon! Read the story at

Intel Blog: Simics 6 Device Register Coverage

I have a new blog post out on the Intel Developer Zone, about the Simics 6 device register coverage feature. I use device register coverage to look at how different operating systems use the same hardware. The differences are significant, demonstrating the (rather expected) observation that different software stacks use the same hardware in different ways.

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Excel 2016 & CSV Import – Hilariously Broken

I just started using Office 365 at work, and almost immediately I hit a hilariously bad problem in the core simple “import CSV” functionality. Basically, the Excel 2016 that I got (it is 2016, not the latest 365 that my home machine all use) does not understand Windows line endings or decimal numbers.

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Using FPGAs to Simulate old Game Consoles

A while ago, Ars Technica reviewed the Mega Sg, a modern clone of the old Sega Genesis gaming system. I stumbled on this review recently and realized that this is a fascinating piece of hardware. The Mega Sg is produced by a company called Analogue (, presumably named thus because they create analogues to old gaming consoles. The way this is done is different from most current “revive the old consoles” products that simply use software emulation to run old games. Instead, Analogue seems to have settled on using FPGA (Field-Programmable Gate Array) technology to basically build new hardware that is functionally equivalent to the old console hardware.

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Off-Topic: Vacation in Crete

This year’s family vacation was spent on the Greek island of Crete, in an all-inclusive resort close to Chania on the north coast. Overall we got nice weather and an enjoyable pool-and-sun holiday, mostly staying at the hotel with a few excursions. In the following, I will go through some of the most surprising or interesting observations I made in Crete. Greek letters are cool, but I do not think we will go back to Greece any time soon when there are higher-quality places available (such as Spain).

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SAMOS 2019 – Insights, Mechanisms, Heterogeneity, and more

Earlier in July 2019, I had the honor of presenting one of the keynote talks at the 19th SAMOS (International Conference on Embedded Computer Systems: Architectures, MOdeling, and Simulation) conference, held on the island of Samos in Greece. When I got the invite, I had no real idea what to expect. I asked around a bit and people said it was a good conference with a rather special vibe. I think that is a very good description of the conference: a special vibe. In addition to the usual papers and sessions, there is a strong focus on community and social events, fostering discussion across academic disciplines and between industry and academia. There were many really great discussions in addition to the paper and keynote presentations, and overall it was one of the most interesting conferences I have been to in recent years.

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A Sudden Case of Cancer

Cancer – it is a scary thing, and it recently became part of my life. It is only two weeks ago today that I got my cancer diagnosis, and I am already out of surgery and recovering. It has been a very speedy process, and hopefully this will be the end of it. Getting a cancer diagnosis is a bit rattling, but there is no reason to panic.

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Intel Blog Post: Clear Linux for Simics Demo & Training

For Simics training and demo purposes, we often use Linux* running on the virtual platforms. In the early days of Simics and embedded Linux, we built our own minimal configurations by hand to run on simple target systems. Most recently, we changed our Linux default demo and training setup to use Clear Linux*. This change showed us just how sophisticated modern Linux setups are – which is good in general, but it also can make some low-level details more complicated.

I wrote an Intel Developer Zone Blog Post about our experience moving to Clear Linux for Simics demos and training, which contains a lot more details of what we observed and did to make this work for our purposes.

DAC 2019 – Cloud, a Book, an Award, and More

Last week was spent at the Design Automation Conference (DAC) in Las Vegas. I had a presentation and poster in the Designer/IP track about Clouds, Containers, and Virtual Platforms , and worked in the Intel Simulation Solutions booth at the show floor. The DAC was good as always, meeting many old friends in the industry as well as checking out the latest trends in EDA (hint: same trends as everywhere else).  One particularly nice surprise was a book (the printed type, not the Vegas “book” that means something else entirely).

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DOOM Black Book – This is Brilliant!

Book cover

I heard about the DOOM Game Engine Black Book by Fabien Sanglard on the Hanselminutes podcast episode 666, and immediately ordered the book. It was a riveting read – at least for someone who likes technology and computer history like I do. The book walks through how the ID Software classic DOOM game from 1993 works and the tricks and techniques used to get sufficient performance out of the hardware of 1993. As background to how the software was written, the book contains a great description of the hardware design of IBM-compatible PCs, gaming consoles, and NeXT machines circa 1992-1994. It covers software design, game design, marketing, and how ID Software worked.

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Intel Blog Post: Simics in the DARPA Cyber Grand Challenge

The US Defense Advanced Projects Agency (DARPA) ran a “Cyber Grand Challenge” in 2016, where automated cyber-attack and cyber-defense systems were pitted against each other to drive progress in autonomous cyber-security. The competition was run on physical computers (obviously), but Simics was used in a parallel flow to check that competitors’ programs were not trying to undermine the infrastructure of the competition rather than compete fairly inside the rules of the competition.

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Living with a Nokia 7.1 Phone

For the past couple of weeks, I have been using a Nokia 7.1 phone as my main phone while my main Sony phone has been off for repairs. My habit for quite a few years has been to use Sony “flagship” phones as my work phones (and way back, even Sony-Ericsson). The question this poses – how was it to use a theoretically far weaker “mid-range” phone instead of a flagship?

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Off-Topic: Windows Explorer Tip: Shift Right-Click

For some reason, Microsoft has decided to hide some decidedly useful features in Windows 10 explorer behind the non-intuitive and rather unknown “shift-key + right-click” combination.

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Off-Topic: The Corsair K55 Rather Silent Keyboard

I have tried yet another keyboard at home in my quest to find one that the rest of the family finds sufficiently silent – while still being nice to type on. While my fingers love the feeling of the super-clicky MX Blues in my K70 at work, it is not the best choice with other people in the same room, especially at home. Thus, my long-running quest for a keyboard with a nice feel but less noise. I started with a Matias Quiet, and when that broke I tried a Corsair RGB Silent Strafe with the rather expensive MX Silent switches. The “silent” was not sufficiently silent, though, bringing me to the latest keyboard I am trying: the Corsair K55 RGB.

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Intel Blog Posts: Running Simics in Containers

Running Simics inside a container is a topic that has come up several times in recent years. In a two-part Intel Developer Zone blog post, my colleague Mambwe Mumbwa and I discuss both some background on container technology, how and how well Simics can run inside of containers, and what you can with containerized Simicses. Overall, containers offer a very good alternative to virtual machines for running programs like Simics, and the tool ecosystem opens up some exciting new ways to manage Simics installations and simulation instances.

Update: this post was extended to link to both part 1 and part 2 of the blog.

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Embedded World 2019

The Embedded World in Nürnberg is still going strong as the best tradeshow for “Embedded” in the world. This year, I spent time doing booth duty and gave a talk in the Conference part of the event. There was an unusual high number of old friends and business acquaintances around, and it was a great experience overall with many fruitful discussions and connections for the future.  However, it seems that there is always something that goes slightly awry with my travel to the show…

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Shifting Left Together at the Embedded World 2019

The Embedded World Exhibition and Conference 2019 is coming up in the last week of February. I will be there presenting a paper in the conference as well as demoing CoFluent in the Intel booth and some other miscellany. The paper “Shifting-Left Together – Enabling the Ecosystem with Virtual Platforms” is about how silicon vendors can (should) use virtual platforms to bring shift-left practices to their customers in addition to their own internal teams.   

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Windows 10 Reboot Loop – CUDA & Alienware

Late last year I was trying to do some machine learning work on my brand new Alienware 15 R4 gaming laptop. I had bought the laptop in order to have something portable with sufficient performance to actually do convolutional neural network (CNN) training and inference “on the road”. The GTX 1060 in the laptop is just as powerful as my home desktop machine, and should run Tensorflow and Keras well. I had the setup working on the desktop already, and copied the code over to the laptop. When trying to run the code the first time, I got some rather strange errors that I finally figured out meant that I was missing the CUDA toolkit. I downloaded CUDA version 10, installed, and the machine rebooted into the Windows 10 automatic repair mode.

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Microsoft REPT: You CAN Reverse from a Core Dump!

There are some things in computing that seem “obviously” true and that “clearly” make it “impossible” to do some things.  One example of this is the idea that you cannot go backwards in time from the current state of a program or computer system and recover previous state by just reversing the semantics of the instructions in the program.  In particular, that you cannot take a core dump from a failed system and reverse-execute back from it – how could you?  In order to do reverse debugging and reverse execution, you “have to” record the state at the first point in time that you want to be able to go back to, and then record all changes to the state. Turns out I was wrong, as shown by a recent Usenix OSDI paper.

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Intel Blog Post: Additional Notes on Temporal Decoupling

A few weeks ago, I talked about temporal decoupling in virtual platforms at DVCon Europe 2018. I just posted some additional notes on the topic temporal decoupling on my Intel blog. In this new blog post, I discuss some more aspects of temporal decoupling, and how it affects simulation semantics. I also explain some of the clever techniques used to minimize the impact of temporal decoupling on the software running on the virtual target system.

Read the full text at as “Additional Notes on Temporal Decoupling“.