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.
Continue reading “Wind River Blog: TCF and Simics”
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.
Schlock Mercenary is a very funny web (and print) comic that I discovered earlier this year via a list at ArsTechnica. In reading up on back issues and back stories, I came across a nice little gem about simulation.
Continue reading “Simulation vs Reality in Schlock Mercenary”
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.
I just added a new blog post at the Wind River blog, about determinism and illustrating Simics-style determinism is by looking at the game Bad Piggies. Games and simulators have quite a lot in common, actually.
Continue reading “Wind River Blog: Simics and Flying Piggies”
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).
Continue reading “Dragons can be Useful – when AT Models Make Sense”
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).
A few years ago, I built a demo on Simics that used a hacked Freescale MPC8641D target that was forced to scale from 1 to 8 cores. Some interesting experiements could be made using this target, and it was nicely scalable for its time. However, I always wanted to have something just a bit bigger. Say 20 cores, or 100. Just to see what would happen. Finally, I got it.
The Simics QSP target that we quietly launched earlier this Summer is such a scalable target. As discussed in a blog post describing the architecture, it is designed to scale to 128 cores currently. Using this ability, I repeated my old experiments, but trying very large threads counts and target core counts. The results show clearly that the way that I coded my parallel computation program was pretty bad, and I really would like to try to rewrite it using some more modern threading library. All I need is time and a way to cross-compile Wool…
Anyway, the new blog post is here.
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.
Continue reading ““Eagle” Cycle-Accurate Simulator Anno 1979″
Carbon Design Systems have been on a veritable blogging spree recently, pushing out a large number of posts around various topics. Maybe a bit brief for my taste in most cases (I have a tendency to throw out 1000+ word pseudo-articles when I take the time to write a blog), but sometimes very interesting nevertheless. I particularly liked a few posts on cache analysis, as they presented some good insight into not-quite-expected processor and cache behaviors.
Continue reading “Some Fun Cache Results from Carbon”
There is a new post at my Wind River blog, about the design and technical contents of the new Simics Quick Start Platforms, more widely known as the QSP. The blog describes the virtual-only hardware that forms part of the QSP, and how it was designed. It is interesting to note that the hardware ended up a bit more complex that I initially thought it would be, since an ideal virtual platform should be very simple. Right? Turns out an OS complicates things.
Continue reading “Wind River Blog: Inside the Simics QSP – Additional Notes”
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.
Continue reading “Youtube Movie on Reverse Execution (and a small bit of Reverse Debug)”
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.
Continue reading “Carbon “Swap ‘n’ Play” – A New Implementation of an Old Idea”
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.
Continue reading “Wind River Blog: Code Coverage over a Back Door”
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.
On my Wind River blog, I just posted a fairly long post about simulation abstraction levels. It was inspired by a cool article in ArsTechnica about Nintendo emulators, and the costs and benefits of being ever more faithful to the hardware.
I just read a quite interesting article by Christian Pinto et al, “GPGPU-Accelerated Parallel and Fast Simulation of Thousand-core Platforms“, published at the CCGRID 2011 conference. It discusses some work in using a GPGPU to run simulations of massively parallel computers, using the parallelism of the GPU to speed the simulation. Intriguing concept, but the execution is not without its flaws and it is unclear at least from the paper just how well this generalizes, scales, or compares to parallel simulation on a general-purpose multicore machine.
Continue reading “GPGPU for Instruction-Set Simulation – Maybe, Maybe not”
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.
All of this can be illustrated by tying shoes.
Just for fun, I tried to surf the web of today using a Netscape 4 browser from 2001.
The result: not exactly useful. Netscape 4 was bad back then, and it does not work at all with the current style of web coding.
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.
I just read an interview with Steve Furber, the original ARM designer, in the May 2011 issue of the Communications of the ACM. It is a good read about the early days of the home computing revolution in the UK. He not only designed the ARM processor, but also the BBC Micro and some other early machines.
Continue reading “Steve Furber: Emulated BBC Micro on Archimedes on PC”
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“.
By chance, I got to attend a day at the UPMARC Summer School with a very enjoyable talk by Francesco Zappa Nardelli from INRIA. He described his work (along with others) on understanding and modeling multiprocessor memory models. It is a very complex subject, but he managed to explain it very well.
Continue reading “Memory Models: x86 is TSO, TSO is Good”
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.