For the past six months I have not been doing much blogging at all, neither here nor on the Wind River blog. The reason is that I have been directing my writing energy into writing a text book about Simics together with Daniel Aarno at Intel. Last year, Daniel and I worked on an Intel Technology Journal issue on Simics. The ITJ issue was kind of a first step on the way to the book, collecting several articles about Simics usage at Intel and elsewhere. The book itself will be much more of a detailed description of Simics and how it works and why it works the way it works.
The September 2013 issue of the Intel Technology Journal (which actually arrived in December) is all about Simics. Daniel Aarno of Intel and I served as the content architects for the issue, which meant that we managed to contributed articles from various sources, and wrote an introductory article about Simics and its usage in general. It has taken a while to get this journal issue out, and now that it is done it feels just great! I am very happy about the quality of all the ten contributed articles, and reading the final versions of them actually taught me some new things you could do with Simics! I already wrote about the issue in a Wind River blog post, so in this my personal blog I want to be a little bit more, well, personal.
On the Wind River blog network, I have a short posting about network simulation with Simics. It points to the network demo video that we put up on Youtube a few weeks ago, along with some explanations of what is shown in the video. In short, we show a simple example of a network being simulated in Simics, along with some examples of what you can do with it.
As an old embedded systems and real-time guy, I have always worked with computer systems that are in some way tied to their environment. Simics has often been used to model such computer systems, inside of customer organizations. Which makes it a bit hard to show… however, recently I have cooked up a demo showing Simics simulating a computer system alongside a physical system.
I just put out a post on the Wind River blog, pointing to both a video of my own “water heater” demo and some other Youtube videos showing Simics integrated with simulations of the real world. A screenshot of my setup in action is shown on the side of this post.
There is a new post at my Wind River blog, featuring a recently-posted video demo of device and systems modeling with Simics. In this video demo, we show an outline of the modeling flow used with Simics 4.8, using only the Eclipse interface. It is actually quite new that we can do this much modeling from within Eclipse; recent efforts in improving the Simics user experience are starting to pay off. As part of the product design team, it feels good to see how even quite small features can really improve the usability of the product.
It is also my first blog post on the recently renovated Wind River blog network. I like the new look of the corporate blog, even if I will have to go back and adjust some older blog images to account for the change from a dark to a light background.
There is a new post at my Wind River blog, where I go back to the basics of reverse execution in Simics and what it can do. The post is not about reverse debugging, about which I have written quite a bit (see for example my series of blog posts: 1, 2, 3, 4, 5, 6), but about the core of reverse execution. I.e., moving the system state back in time in a variety of ways. There is an accompanying video demo on Youtube.
There is a new post at my Wind River blog, about how some new features in Simics 4.8 improve the collaboration power of Simics checkpoints. For the first time, Simics checkpoint can now carry a piece of history (slice of time), which also makes reverse execution and reverse debug work with checkpoints in a logical way.
Simics 4.8 is finally released, and I put up a blog post explaining the most important news in this release. It is two years since we released Simics 4.6, so there is quite a bit of news in Simics 4.8 – even though lots of functionality has been released continuously into 4.6 over the past twenty four months. My personal favorite are the comments you can put on an execution and the stop log, but then again, that might be because they have been a couple of pet ideas of mine so I am hardly an impartial judge. Everything else is also really good, and the engineering teams and marketing teams involved have put in a lot of effort into this release (as we do in all releases).
There is a new post at my Wind River blog, about how I ran a Windows file share server (CIFS) on a Simics-simulated VxWorks big-endian Power Architecture target. Something that just should work, given that the software in question is known to work in the real world. But still, pretty cool, and a bit eerie.
On my Wind River blog, you can now find a description on how we have used the Eclipse TCF (target connection framework) to build the Simics GUI. Or rather, the connection between the Simics GUI and the Simics simulation process. It is actually quite revolutionary what you can do with the TCF, compared to older debug protocols. In particular, TCF lets you combine many different services across a single connection.
Last year, I did a Simics webinar which included a two-part demo of how to use Simics to debug an endianness bug in a networked system as it migrates from big-endian to a little-endian system. Along the way, I also showed off various Simics features like reverse execution and checkpointing and scripted execution.
The demo is now online at the Wind River Youtube channel, and the setup is explained in a blog post at the Wind River company blog which is worth reading before watching the video.
There is a new post at my Wind River blog, telling the story of how some of the Simics developers used Simics itself to debug an intermittent Simics program crash caused by a timing-sensitive race condition.
Running Simics on itself is pretty cool, and shows the power of the simulator and its applicability even to really complex software.
Carbon Design Systems keeps putting out interesting blog posts at a good pace. Bill Neifert at recently put up a blog post about the various of speed/accuracy tradeoffs you can make when building virtual platforms. The main message of the blog is that you should use a mix of fast models (TLM + JIT, like the ARM Fast Models) and cycle-accurate generated-from-RTL models (like the models generated by Carbon’s tools). By switching between the levels of abstraction when you need to go fast or go deep, you get something that is pretty much the best of both worlds (I already blogged about the change between abstraction before). It makes perfect sense, and I am all with him. There are dragons in the middle land.
However, I do not quite agree with Bill about the absolute uselessness of the intermediate types of models, like SystemC TLM-2.0 AT. Basically, what is traditionally called “cycle accurate modeling” (while not derived from RTL).
I am going to be talking about how to transport bugs with virtual platform checkpoints, in the Software Tools track at the Embedded Conference Scandinavia, on October 3, 2012, in Stockholm (Sweden). The ECS is a nice event, and there are several tracks to choose from both on October 2 and October 3. In addition to the tracks, Jan Bosch from Chalmers is going to present a keynote that I am sure will be very entertaining (see my notes from a presentation he did in Göteborg last year).
I recently read the classic book The Soul of a New Machine by Tracy Kidder. Even though it describes the project to build a machine that was launched more than 30 years ago, the story is still fresh and familiar. Corporate intrigue, managing difficult people, clever engineering, high pressure, all familiar ingredients in computing today just as it was back then. With my interesting in computer history and simulation, I was delighted to actually find a simulator in the story too! It was a cycle-accurate simulator of the design, programmed in 1979.
We just uploaded a short movie about reverse execution and reverse debugging to Youtube, to the Wind River official channel. In the short time available in this demo, we really only show reverse execution. Reverse debug, as I define it, is not used much at all, as explaining what goes on when you start to put breakpoints into a program and analyze its behavior takes a surprising amount of time.
On the Wind River corporate blog, I have put up a blog post about how Wind River Education Services is going to use Simics to teach networking. What is interesting with this approach is that it shows how a virtual platform can be used for tasks like teaching that don’t have much to do with hardware modeling or similar “typical” VP uses. In this case, the key value is encapsulation of a set of machines running real operating systems and software stacks, and with lots of networks connecting them.
There is a new post at my Wind River blog, about how a team of researchers at the University of Nebraska at Lincoln is using Simics to force rare bugs to manifest themselves as errors. They used Simics to control a target system to force it into rare situations much more likely to trigger latent bugs, requiring far fewer test runs compared to just randomly rerunning tests again and again and hoping to see a bug.
Carbon Design Systems have been quite busy lately with a flurry of blog posts about various aspects of virtual prototype technology. Mostly good stuff, and I tend to agree with their push that a good approach is to mix fast timing-simplified models with RTL-derived cycle-accurate models. There are exceptions to this, in particular exploratoty architecture and design where AT-style models are needed. Recently, they posted about their new Swap ‘n’ Play technology, which is a old proven idea that has now been reimplemented using ARM fast simulators and Carbon-generated ARM processor models.
There is a new post at my Wind River blog, about how the LDRA code coverage tools have been brought to work on Simics using a simulation-only “back door “.
The most interesting part of this is how a simulator can provide an easy way to get information out of target software, without all the software and driver overhead associated with doing the same on a real target. In this case, all that is needed is a single memory-mapped location that can written to be software – which can be put into user-mode-accessible locations if necessary.
Wind River recently added a couple of new processor models to Simics: the 30-year-old 80186 and the 32-year-old 8051.
I have a blog post about this up on the Wind River tools blog. Pretty amazing to see us model an eight bit machine in 2012 – just proves how long-lived some hardware systems are.
There is a new post at my Wind River blog, about Simics running a model of the new Intel Crystal Forest platform. Crystal Forest is a very complex piece of hardware, but I am pretty happy that we managed to demo it in an understandable way – by essentially using it as a black box and putting a pretty display on top of that (using Eclipse).
There is a new post at my Wind River blog, an interview with Dan Poirot at RTI who is using Simics to model and test heterogeneous, distributed, networked systems.
I just had two articles published the Embedded Design part of the EETimes.
First, “Rethink your project planning with a virtual platform“, which talks about how virtual platforms can change your entire project planning. Essentially, by reducing project friction and risks related to hardware availability, software integration, and show-stopper bugs, you can make projects work much better.
Then we have “Transporting bugs with virtual checkpoints“, which is a shorter, popular science, version of the paper I published last year at S4D. This describes how you can use checkpointing in a virtual platform to communicate bugs across time, space, and teams.
There is a new post at my Wind River blog, which could seem to be about shoes but which is really about process improvement. In particular, the need for companies to let their employees take a step or two back and look at what they are doing and what they could do better.
It is way too common to be so busy running around being inefficient that there is no time to think about how to become more efficient. Change also requires some discipline to actually keep pushing at habits until they change for the better.
There is a new post at my Wind River blog, about hypersimulation in virtual platforms and how it lets virtual time fly much faster than real time. It was the result of simple mistake of leaving Simics running in the background as I did other work on my machine.
There is a new post at my Wind River blog, about how you build virtual platforms with Simics. The post is more about the methodology than the nature of models, cycle accuracy, endianness, and all the other details of virtual platform modeling. I have written about modeling methodology on this blog too, and in particular I would recommend looking at “Two perspectives on modeling“.
There is a new post at my Wind River blog, about the new Simics 4.6 release. 4.6 has some serious new goodies in it, including an Eclipse source-code debugger and a way to build blinking lights front panels for boards.
Since I have a certain interest in debugging, I was happy find the article “Guidelines for SystemC – Debugger Integration” at the usually interesting Design and Reuse website. However, I must say that it was pretty disappointing.
There is a new post at my Wind River blog, about how Simics was used to kick-start the development of the 64-bit version of VxWorks. It is an interesting example of how to use a virtual platform as a model of something much simpler and gentler than actual hardware systems.