Opinion

Jeff Bier’s Impulse Response—Multiprocessors: Back to the Drawing Board

You’ve probably been hearing a lot of buzz lately about multiprocessor chips. Putting multiple processors on a chip isn’t a new idea, of course. But such chips are gaining significant momentum both in general-purpose computing applications and in embedded systems. In the world of embedded digital signal processing applications, multiprocessor chips are becoming attractive for an expanding range of systems—even cost-sensitive applications like consumer products. As a result, effective software Read more...

Jeff Bier’s Impulse Response—Bamboozling with Benchmarks, Part 2

In the February 2006 column, I listed four of the Top Ten ways in which processor benchmark results are commonly misused. This month I’ll cover the remaining six. If you rely on benchmark results, you’ll want to watch out for these. Comparing projected benchmark results for a chip that doesn’t yet exist to results for a chip that does. Mixing projected and actual benchmark results isn’t necessarily bad (and can be quite informative) but there are a couple of ways in which it can be Read more...

Jeff Bier’s Impulse Response—Bamboozling with Benchmarks, Part 1

My colleagues and I at BDTI believe very strongly in benchmarks. We’ve been developing and implementing signal processing benchmarks for over a decade, and we know that good benchmarks play an essential role in evaluating processing engines. You can see, then, why we get bent out of shape when benchmarks are used misleadingly. This happens pretty regularly in vendor marketing materials, but we’ve also seen it in training classes and technical articles. Most people don’t set out to use Read more...

Jeff Bier’s Impulse Response—Are DSPs Disappearing?

Looking back at the past year, a striking trend emerges: Increasingly, the hardware used for signal processing is something other than a DSP. I made a quick survey of the year’s developments by skimming the archives on www.bdti.com/InsideDSP. I discovered that only about half of the chips BDTI wrote about in 2005 were DSPs. The rest of the chips were general-purpose processors, FPGAs, or other types of hardware. Admittedly, this hardly qualifies as a scientific survey, but the results reflect Read more...

Jeff Bier’s Impulse Response—When Scaling Gets Squirrelly

It’s so tempting. You need to figure out how much processing power you’ll require to implement a particular video compression algorithm, and there, out on the Web, is the data you need—but for a slightly different scenario. Perhaps the data is for a smaller frame size than what you have in mind. Or maybe it’s for a low compressed bit rate, and your application will be using a higher one. You tell yourself, “Well, I don’t have the exact data I need, so I’ll just multiply the data I do have Read more...

Jeff Bier’s Impulse Response—Suboptimal Optimization

Those of us who earn our livelihoods working with embedded signal processing software understand that optimization isn’t just something we do for fun (though often it is quite fun). Optimization is usually done to meet hard real-time constraints, trim product costs, or stretch battery life. We all know that the complexity of the processor core has a significant impact on how difficult it will be to optimize the code. But more and more, it’s critical to also consider the complexity of the Read more...

Jeff Bier’s Impulse Response—Video Processors: Why the Rush?

In the last year or so I have noticed an impressive surge in new processors targeting digital video applications. Hardly a month goes by without a vendor announcing that it has the ultimate video processor. Countless new companies have sprung up to address this hot market, and established processor vendors are scrambling to re-spin their offerings for digital video. Why is everyone suddenly so eager to market a digital video processor? One reason is that digital video products show great Read more...

Jeff Bier’s Impulse Response—And Now a Word from Our Sponsor

I’m usually an easy-going guy, but there are some things I really hate. For example, I hate the bait-and-switch: it makes me cranky when someone offers me something that looks appealing, only to later substitute something much less attractive. Along these same lines, I hate it when I pay upwards of $1000 to attend a technical conference only to find myself sitting in a presentation that is, essentially, an advertisement. Why should I pay good money to hear a company promote itself? I can Read more...

Jeff Bier’s Impulse Response—Slower is Better!

When people talk about processor benchmarks, the conversation usually ends up being all about speed. Other metrics, such as energy efficiency, are often given less attention or are completely overlooked. The unspoken assumption driving these conversations is that a faster processor is better. For most embedded signal processing applications, this assumption doesn’t make sense. These applications usually have fixed processing requirements. Typically, the goal is to meet those requirements Read more...

Jeff Bier’s Impulse Response—Making Benchmarks Useful

A few weeks ago I participated in a panel discussion on benchmarking. The theme of the panel was how to benchmark multi-threaded and multi-core processors. In my view, this theme highlights a key problem with many benchmark approaches: too many benchmarks are designed to exercise hardware features, rather than to provide information that system developers need. In most embedded applications, system developers care about high-level system attributes such as low cost, long battery life, Read more...