Category: history of computing

A new (and old) Reverse Debugger – Microsoft WinDbg

A blog post from Undo Software informed me that Microsoft has rather quietly released a reverse debugger tool for Windows programs – WinDbg with Time Travel Debug. It is available in the latest preview of WinDbg, as available through the Windows Store, for the most recent Windows 10 versions (Anniversary update or later). According to a CPPcon talk about the tool (Youtube recording of the talk) the technology has a decade-long history internally at Microsoft, but is only now being released to the public after a few years of development. So it is a new old thing 🙂

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Simulation in the IBM ACS Project – Current Practices in 1966

I once wrote a blog post about the use of computer architecture pipeline simulation in the IBM ”Stretch” project, which seems to be the first use of computer architecture simulation to design a processor. After the ”Stretch” machine, IBM released the S/360 family in 1964. Then, the Control Data Corporation showed up with their CDC 6600 supercomputer, and IBM started a number of projects to design a competitive high-end computer for the high-performance computing market.  One of them, Project Y, became the IBM Advanced Computing Systems project (ACS). In the ACS project, simulation was used to document, evaluate, and validate the very aggressive design. There are some nuggets about the simulator strewn across historical articles about the ACS, as well as an actual technical report from 1966 that I found online describing the simulation technology! Thus, it is possible to take a bit of a deeper look at computer architecture simulation from the mid-1960s.

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Simulation and the Apollo Guidance Computer

Today, when developing embedded control systems, it is standard practice to test control algorithms against some kind of “world model”, “plant model” or “environment simulator”.

Using a simulated control system or a virtual platform running the actual control system code, connected to the world model lets you test the control system in a completely virtual and simulated environment (see for example my Trinity of Simulation blog post from a few years ago). This practice of simulating the environment for a control computer is long-standing in the aerospace field in particular, and I have found that it goes back at least to the Apollo program.

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How 3dfx was Built on a Simulator

This blog post was originally published at Intel. After it was retired from the Intel blog system, I reposted the full contents here in order to preserve the information for my own sake. And in case anyone has a pointer here.

How Simulation Started a Billion-Dollar Company

In the early 1990s, “PC graphics” was almost an oxymoron. If you wanted to do real graphics, you bought a “real machine”, most likely a Silicon Graphics workstation. At the PC price-point, fast hardware-accelerated 3D graphics wasn’t doable… until it suddenly was, thanks to Moore’s law. 3dfx was the first company to create fast 3D graphics for PC gamers.  To get off the ground and get funded, 3dfx had to prove that their ideas were workable – and that proof came in the shape of a simulator.  They used the simulator to demo their ideas, try out different design points, develop software pre-silicon, and validate the silicon once it arrived. 

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A Replay Debugger from 1995!

2016-06-05_21-29-16A comment on my old blog post about the history of reverse execution gave me a pointer to a fairly early example of replay debugging. The comment pointed at a 2002 blog post which in turn pointed at a 1999 LWN.net text which almost in passing describes a seemingly working record-replay debugger from 1995. The author was a Michael Elizabeth Chastain, of whom I have not managed to find any later traces.

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Fortress Rochester

fortress rochester

In a dusty bookshelf at work I found an ancient tome of wisdom, long abandoned by its previous owner. I was pointed to it by a fellow explorer of the dark arts of computer system design as something that you really should read. The book was “Fortress Rochester”, written by Frank Soltis, and published in 2001.

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Why DO Computers Fail?

tandem2

I just found and read an old text in the computer systems field, “Why Do Computers Fail and What Can Be Done About It?” , written by Jim Gray at Tandem Computers  in 1985. It is a really nice overview of the issues that Tandem had encountered in their customer based, back in the early 1980s. The report is really a classic in the computer systems field, but I did not read it until now. Tandem was an early manufacturer of explicitly fault tolerant and highly reliable and available computers. In this technical report Jim Gray describes the basic principles of fault tolerance, and what kinds of faults happen in the field and that need to be tolerated.

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The First 64-bit Phone

apple_A7_image

Apple just released their new iPhone 5s, where the biggest news is really the 64-bit processor core inside the new A7 SoC. Sixty four bits in a phone is a first, and it immediately raises the old question of just what 64 bits gives you. We saw this when AMD launched the Opteron and 64-bit x86 PC computing back in the early 2000’s, and in a less public market the same question was asked as 64-bit MIPS took huge chunks out of the networking processor market in the mid-2000s. It was never questioned in servers, however.

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Reverse Execution History Updates

After some discussions at the S4D conference last week, I have some additional updates to the history and technologies of reverse execution. I have found one new commercial product at a much earlier point in time, and an interesting note on memory consistency.

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“Eagle” Cycle-Accurate Simulator Anno 1979

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.

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Reverse History Part Three – Products

In this final part of my series on the history of reverse debugging I will look at the products that launched around the mid-2000s and that finally made reverse debugging available in a commercially packaged product and not just research prototypes. Part one of this series provided a background on the technology and part two discussed various research papers on the topic going back to the early 1970s. The first commercial product featuring reverse debugging was launched in 2003, and then there have been a steady trickle of new products up until today.

Originally published in January 2012. Post updated 2012-09-28 with a revised timeline for Lauterbach CTS. Post updated 2016-04-05 to include Mozilla RR. Post updated 2016-12-26 to add Simulics. Post updated 2017-10-08 to add Microsoft WinDbg. Post updated 2018-07-28 to add Borland Turbo Debugger.

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Reverse History Part Two – Research

This is the second post in my series on the history of reverse execution, covering various early research papers. It is clear that reverse debugging has been considered a good idea for a very long time. Sadly though, not a practical one (at the time). The idea is too obvious to be considered new. Here are some of the papers that I have found, going back before reverse debugging got started for real in actual products (around 2003) as well later on for interesting research papers that did not make it into products.  It is worth noting that products/useful software has become more common in recent times as the way that reverse debugging ideas get expressed.

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Reverse History Part One

For some reason, when I think of reverse execution and debugging, the sound track that goes through my head is a UK novelty hit from 1987, “Star Trekkin” by the Firm. It contains the memorable line “we’re only going forward ’cause we can’t find reverse“. To me, that sums up the history of reverse debugging nicely. The only reason we are not all using it every day is that practical reverse debugging has not been available until quite recently.  However, in the past ten years, I think we can say that software development has indeed found reverse.  It took a while to get there, however. This is the first of a series of blog posts that will try to cover some of the history of reverse debugging. The text turned out to be so long that I had to break it up to make each post usefully short. Part two is about research, and part three about products.
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DV* 30 Years

On the very binary date of 11-11-11, my alma mater, the computer science (DV, for datavetenskap) education at Uppsala University celebrated its thirty years’ anniversary. It was a great classic student party in the evening with a nice mix of old alumni and fresh-faced students. Lots of singing and some nice skits on stage. Great fun, and my voice has still not recovered. It also got me thinking about it is that we really do as computer scientists.

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