I am going to present a paper about our new SystemC Library in Simics, at the DVCon Europe conference taking place in München next month. The paper is titled “Integrating Different Types of Models into a Complete Virtual System – The Simics SystemC* Library”, and I authored it together with my Intel colleagues Andreas Hedström, Xiuliang Wang, and Håkan Zeffer.
I was at the DAC 2016 conference and exhibition in Austin, Texas, a few weeks ago. On the show floor, going by the S2C booth, I was roped in and got a paper copy of the book Prototypical. The copy was even signed by the authors Daniel Nenni and Don Dingee! Nice touch! The book is more than just marketing material – it provides a good overview of the origins and history of FPGA prototyping, and I found it nice and enjoyable to get more insights into this fairly important part of the EDA tools ecosystem.
A long time ago, when I was a PhD student at Uppsala University, I supervised a few Master’s students at the company CC-Systems, in some topics related to the simulation of real-time distributed computer systems for the purpose of software testing. One of the students, Magnus Nilsson, worked on a concept called “Time-Accurate Simulation”, where we annotated the source code of a program with the time it would take to execute (roughly) on the its eventual hardware platform. It was a workable idea at the time that we used for the simulation of distributed CAN systems. So, I was surprised and intrigued when I saw the same idea pop up in a paper written last year – only taken to the next level (or two) and used for detailed hardware design!
Continue reading “Time-Accurate Simulation Revisited – 15 years later”
I had the great honor to be on a panel discussing IoT Security at the DAC back in June. The panel was part of the Embedded Techcon event that took place essentially as a little embedded corner inside the DAC – it was held in a couple of conference rooms next to the regular DAC sessions, and attendees were also mostly attending the DAC in general. Not a bad idea for meshing embedded and hardware design. The panel was a great one, and David Kleidermacher from Blackberry gave me a great take-away: unless security is allowed to gate releases of products, it is hard to think you take security seriously.
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.
Last week, I attended my fourth System, Software, SoC and Silicon Degug conference (S4D) in a row. I think the silicon part is getting less attention these days, most of the papers were on how to debug software. Often with the help of hardware, and with an angle to how software runs in SoCs and systems. I presented a paper reviewing the technology and history of reverse debugging, which went down pretty well.
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.
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.
Recently, Gary Stringham has been running a series of interviews with providers of register design tools on his website. Register design tools seems to be an active area with several small companies (and some open-source tools) fighting for the market. I have written about Gary Stringham and register designs before, and it is an area that keeps fascinating me. There is something about the task of register design that keeps it separate from the main hardware design languages, tools, and flows.The different approaches taken by the tools supporting the register design task also illustrates some points about programming language standards, domain-specific languages, and exchange formats that I want to address.
James Aldis of TI has published an article in the EEtimes about how Texas Instruments uses SystemC in the modeling of their OMAP2 platform. SystemC is used for early architecture modeling and performance analysis, but not really for a virtual platform that can actually run software. The article offers a good insight into the virtual platform use of hardware designers, which is significantly different from the virtual platform use of software designers.
Continue reading “EETimes: James Aldis on Performance Modeling”
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.
Looks like S4D (and the co-located FDL) is becoming my most regular conference. S4D is a very interactive event. With some 20 to 30 people in the room, many of them also presenting papers at the conference, it turns into a workshop at its best. There were plenty of discussion going on during sessions and the breaks, and I think we all got new insights and ideas.
This post features some additional notes on the topic of transporting bugs with checkpoints, which is the subject of a paper at the S4D 2010 conference.
The idea of transporting bugs with checkpoints is some ways obvious. If you have a checkpoint of a state, of course you move it. Right? However, changing how you think about reporting bugs takes time. There are also some practical issues to be resolved. The S4D paper goes into some of the aspects of making checkpointing practical.
I have a paper about “Transporting Bugs with Checkpoints” to be presented at the S4D (System, Software, SoC and Silicon Debug) conference in Southampton, UK, on September 15 and 16, 2010. The core concept presented is to leverage Simics checkpointing to capture and move a bug from the bug reporter to the responsible developer. It is a fairly simple idea, but getting it to work efficiently does require that some things are done right. See the longer Wind River blog posting about this topic for a few more details.
The discussion on my previous blog post about “the ideal ESL language” made me think some more about the purpose of a hardware modeling or description language. If you look closely, you realize that there are two quite different goals being pursued by the tools and languages discussed there.
On one hand, we have the task of supporting the design of new hardware bits, for the purpose of creating it. On the other hand, we have the task of describing a particular design for the purpose of simulating it. These two are not necessarily the same.
In his most recent Embedded Bridge Newsletter, Gary Stringham describes a solution to a common read-modify-write race-condition hazard on device registers accessed by multiple software units in parallel. Some of the solutions are really neat!
I have seen the “write 1 clears” solution before in real hardware, but I was not aware of the other two variants. The idea of having a “write mask” in one half of a 32-bit word is really clever.
However, this got me thinking about what the fundamental issue here really is.
Continuing on my series of posts about checkpointing in virtual platforms (see previous posts Simics, Cadence, our FDL paper), I have finally found a decent description of how CoWare does things for SystemC. It is pretty much the same approach as that taken by Cadence, in that it uses full stores a complete process state to disk, and uses special callbacks to handle the connection to open files and similar local resources on a system. The approach is described in a paper called “A Checkpoint/Restore Framework for SystemC-Based Virtual Platforms”, by Stefan Kraemer and Reiner Leupers of RWTH Aachen, and Dietmar Petras, and Thomas Philipp of CoWare, published at the International Symposium on System-on-Chip, in Tampere, Finland, in October of 2009.
This post is a belated comment on the FDL 2009 conference that I attended some months ago. I have had some things in mind for a while, but some recent podcast listening has brought the issues to front again. What has been striking is the extent to which FDL was about languages only to a very small degree. Compared to programming-language conferences like PLDI, there was precious little innovation going on in input languages, and very little concern for the programming aspects of virtual platform design and hardware modeling.
SCDSource ran a short but good article summarizing a few DAC talks that I would liked to attend. it mostly about the experience of long-term parallel programming research David Bailey in presenting results in the field…
An unplanned and unexpected bonus with my trip to the FDL 2009 conference was the co-located S4D conference. S4D means System, Software, SoC and Silicon Debug, and is a conference that has grown out of some recent workshops on the topic of debugging, as seen from the perspective of hardware designers (mostly). S4D was part of the same package as FDL and DASIP, entrance to one conference got you into the other two too. As I did not know about S4D until quite late in the process, this was a great opportunity for me to look at what they were doing.
This is end of the second day of FDL 2009, and it is proving to be quite an interesting experience. The location is very bad, apart from the weather (coming from a Swedish Fall where temperatures are dropping towards 10 C, to a sunny 27 C is quite nice). But Sophia Antipolis is just a tech park with some hotels, and you cannot get anywhere interesting or civilized without a car. No shops, no restaurants except for hotels, and so sidewalks in parts.
But the conference is good enough to be worth the bodily discomforts. And I did find a nice Parcours Sportif for the morning run, as well as a nice breakfast buffet at the Mercure Hotel.
The paper will explain how we did Simics-style checkpointing in SystemC, using the GreenSocs GreenConfig mechanisms to obtain an approximation for the Simics attribute system.
This post is a follow-up to the DAC panel discussion we had yesterday on how to conquer hardware-dependent software development. Most of the panel turned into a very useful dialogue on virtual platforms and how they are created, not really discussing how to actually use them for easing low-level software development. We did get to software eventually though, and had another good dialogue with the audience. Thanks to the tough DAC participants who held out to the end of the last panel of the last day!
As is often the case, after the panel has ended, I realized several good and important points that I never got around to making… and of those one struck me as worthy of a blog post in its own right.It is the issue of how high-level synthesis can help software design.
The past few days here at DAC, a big theme has been transaction level modeling (TLM).
TLM is often considered to be SystemC TLM-2.0. Most of the statements from the EDA companies are to the effect that SystemC TLM-2.0 solves the problem of combining models from different sources. Scratching the surface of this happy picture, it is clear that it is not that simple…
I finally got to spend some time at the DAC show floor on Thursday (which was day four and the last day of the show). It was very quiet, not many people around, and many booths also running with low staffing. However, unlike the Embedded Systems Conference, this last day was not indicative of the show overall.
The 46th Design Automation Conference (DAC) is coming up in San Francisco in the US, last week of July. For me, this will be the first time I ever go to DAC. I have been to a couple of Design Automation and Test Europe (DATE) conferences before, but DAC is supposedly even bigger as an event for the EDA and related communities. I have the honor to be on a panel this year, as well as co-authoring a paper on software validation.
Another Cadence guest blog entry, about the overall impact of virtual platforms on the interaction between hardware and software designers. Essentially, virtual platforms are a great tool to make software and hardware people talk to each other more, since it provides a common basis for understanding.
Virtutech and Cadence yesterday announced the integration of Virtutech Simics and Cadence ISX (Incisive Software Extensions), which is essentially a directed random test framework for software. With this tool integration, you can systematically test low-level software and the hardware-software (device driver) interface of a system, leveraging a virtual platform.