Tag Archives: Clock-cycle Models

Dragons can be Useful – when AT Models Make Sense

2012 November 12 15:51 / 4 Comments /

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).

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Posted in: computer simulation technology, virtual platforms / Tagged: , , , ,

Pipeline Performance Simulator Anno 1960

2010 May 3 20:56 / 1 Comment /

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 IBM.com).

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Posted in: computer architecture, computer simulation technology, history of computing / Tagged: , , , , , , , ,

Adding to Schirrmeister’s Virtual Platform Myth Busting

2009 February 18 13:22 / 2 Comments /

opinionFrank Schirrmeister of Synopsys recently published a blog post called “Busting Virtual Platform Myths – Part 1: “Virtual Platforms are for application software only”. In it, he is refuting a claim by Eve that virtual platforms are for application-level software-development only, basically claiming that they are mostly for driver and OS development and citing some Synopsys-Virtio Innovator examples of such uses. In his view, most appication-software is being developed using host-compiled techniques.  I want to add to this refutal by adding that application-software is surely a very important — and large — use case for virtual platforms.

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Posted in: embedded software, embedded systeme, ESL, multicore software, programming, virtual platforms / Tagged: , , , , , , , , , ,

Notes from the IP 08 Panel

2008 December 6 22:31 / 3 Comments /

Now I am home again, and some days have passed since the IP 08 panel discussion about software and hardware virtual platforms. This was an EDA hardware-oriented conference, and thus the audience was quite interested in how to tie things to hardware design. Any case, it was a fun panel, and Pierre Bricaud did a good job of moderating and keeping things interesting.

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Posted in: appearances, computer simulation technology, conferences, EDA, ESL, programming, virtual platforms / Tagged: , , , , , , ,

Is Cycle Accuracy a bad Idea?

2008 July 11 22:45 / 8 Comments /

In a funny coincidence, I published an article at SCDSource.com about the need for cycle-accurate models for virtual platforms on the same day that ARM announced that they were selling their cycle-accurate simulators and associated tool chain to Carbon Technology. That makes one wonder where cycle-accuracy is going, or whether it is a valid idea at all… is ARM right or am I right, or are we both right since we are talking about different things?

Let’s look at this in more detail.

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Posted in: computer simulation technology, EDA, ESL, virtual platforms / Tagged: , , , , , , , , , , , , , ,

SCDSource Article: Combining Fast and Detailed Models

2008 July 11 21:50 / 1 Comment /

I have another opinion piece published over at SCDsource.com. The title, “Why virtual platforms need cycle-accurate models“, was their creation, not mine, and I think it is a little bit off the main message of the piece.The follow-up discussion is also fairly interesting.

The key thing that I want to get across is that we need virtual platforms where we can spend most of our time executing in a fast, not-very-detailed mode to get the software somewhere interesting. Once we get to the interesting spot, we can then switch to more detailed models to get detailed information about the software behavior and especially its low-level timing. Getting to that point in detailed mode is impossible since it would take too much time.

This is something that computer architecture researchers have been doing for a very long time, just look at how toolsets like SimpleScalar and Simics with the Wisconsin GEMS system use fast mode for “positioning” and more detailed execution for “measurement”. It is also what is now commercial with the Simics Freescale QorIQ P4080 Hybrid virtual platform. Tensilica also have the ability to switch mode in their toolchain.

See an upcoming post for more on how to get at the cycle-accurate models – this was just to point out that that the article is there, for symmetry with previous posts about my articles popping up in places.

Posted in: articles, computer simulation technology, EDA, embedded software, ESL, multicore software, virtual platforms / Tagged: , ,

Freescale QorIQ P4080 Hybrid Simulation on YouTube(!)

2008 June 18 10:25 / 3 Comments /

YouTube – Freescale QorIQ P4080 Hybrid Simulation is a video of a demo of the QorIQ P4080 hybrid simulation. Cool of Freescale to be publishing it like this, I think it is a very smart move!

Updated: Here is the video inline, let’s see if this works.

Posted in: business issues, computer simulation technology, ESL, multicore computer architecture, virtual platforms / Tagged: , , , , , ,

Is SoC (was: ESL) all there is to virtual platforms?

2008 June 11 22:19 / 6 Comments /

SystemC TLM-2.0 has just been released, and on the heels of that everyone in the EDA world is announcing various varieties of support. TLM-2.0-compliant models, tools that can run TLM-2.0 models, and existing modeling frameworks that are being updated to comply with the TLM-2.0 standard. All of this feeds a general feeling that the so-called Electronic System Level design market (according to Frank Schirrmeister of Synopsys, the term was coined by Gary Smith) is finally reaching a level of maturity where there is hope to grow the market by standards. This is something that has to happen, but it seems to be getting hijacked by a certain part of the market addressing the needs of a certain set of users.

There is more to virtual platforms than ESL. Much more. Remember the pure software people.

Edit: Maybe it is more correct to say “there is more to virtual platforms than SoC”, as that is what several very smart comments to this post has said. ESL is not necessarily tied to SoC, it is in theory at least a broader term. But currently, most tools retain an SoC focus.

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Posted in: computer simulation technology, embedded software, embedded systeme, ESL, multicore computer architecture, programming, virtual platforms / Tagged: , , , , , ,