Date:
Monday , September 18, 2006
Author:
Kyle Bennett
Editor:
Joey Seiler
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AMD Quad Core Discussion & Editorial

A chat with AMD's CTO about the upcoming K8L Quad Core AMD processor gives us some new insight as to just how AMD is looking to handle the newly competitive market served up by Intel's Core 2 Duo and beyond.

Introduction

A couple of weeks ago I had the opportunity to sit down and chat with Phil Hester, Senior VP and CTO of AMD, and also have a phone conversation with AMD Senior Technical Architect Pat Conway. I would like to take this time to talk about some of the issues we covered while peppering the information with my own thoughts.

When I talk to upper-ranking executives with tech companies, I like to ask, “Do you build your own machines?” Phil let me know that, like many [H] enthusiasts, he had been experimenting with his own AMD 4X4 box. He and his son are currently sharing a dual-processor, dual-core system based on a Tyan workstation board. You have to appreciate a CTO that still gets his hands dirty like the rest of us, and it goes a long ways towards letting me know that this guy really does know what is going on at an enthusiast level. If you understand that, you’ll know where the market is moving.

What’s in a Name?

Our conversations covered many topics, but of course I am most interested in AMD’s next-generation desktop processors. Many of us have seen this technology referred to as AMD’s “K8L” architecture, but AMD wants to stay away from codenames altogether, as they undermine AMD’s branding initiatives with Opteron, Athlon, and Sempron. According to Phil Hester, “The K8L name has a life of its own.”

Since many folks still refer to the Intel Core 2 Duo as the “Conroe” and many others wonder what they are talking about, I can see where AMD is coming from. The hardware enthusiast crowd is all about code names, though. The names let enthusiasts in the know represent a special knowledge and feel a connection to the technology. It’s a bonding process.

Regardless, “Next-Generation Processor Technology” is a bit dry. Given that AMD officials have been quoted using the “K8L” code name, I’ll stick with that for this article, but AMD wants you to remember it as an Opteron or Athlon when it is unveiled.

Update: 5PM CDT 9/18/06 – AMD has contacted me with information that backtracks on all of the branding information above. AMD has chosen to refer to the quad core code name for this next gen processor as “Barcelona.”

The Barcelona Facts

AMD’s Barcelona is a native quad-core die design as shown in this representation. Referring to this as “native” is a strike at some of Intel’s previous dual-core designs and their upcoming “Kentsfield” quad-core processor that is simply two Core 2 Duo processors placed side by side on a single package. “Native” highlights the technology as new, not just two older technologies dropped onto a single piece of silicon.

The new quad core is all about parallelism and power—and using that power sparingly. Consider the Barcelona as four processors laid on a single silicon die that have had a new cache support and interconnect technologies bound around them to make them work more efficiently. The most obvious change we will see will be the addition of a shared L3 cache. This new L3 cache, debuting at 2MB in Athlons and Opterons, will be used by all four cores. Each core will also have their own smaller L1 (64KB) and L2 (512KB) caches that can be shared by all the cores as well. This moves towards latency reduction in an attempt to lay the hardware groundwork for truly parallel software programming that can use all the cores simultaneously.

Another key here is controlling these cores. Certainly there is no need for all four cores to be running all the time, and AMD has implemented some spiffy controls when it comes to the Barcelona. There are basically nine knobs that can be turned to effect clock rates and voltages. The clock generators, or PLLs as they are commonly called, reside on each core of the quad-core processor. They are also present on other components as well. This allows AMD to run a single core on the processor at full load while the others remain dormant, or it allows the system to scale the cores independently. To put it simply, the cores only receive the power that they need when they need it.

Now many of us enthusiasts know that true parallel software is hard to find once you leave the video and audio encoding segments. And many of us are concerned with games. This is where Instructions Per Clock (IPC) come in.

IPC and Power Envelope

When talking to both Phil and Pat, we got some interesting answers about advancements in Instructions Per Clock with the Barcelona Pat Conway said that we will see a “performance improvement of 150% over the next two years that will be within the same power envelope.” If you take into account that you can back off frequency and add more cores, some of this can be achieved now if you are counting IPC across all cores. (See below how simply pulling back on frequency by as little as 16% can have a huge impact on power draw.) Intel is bound by the same principles as well.

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On IPC and AMD’s Barcelona Phil Hester had this to say: “We want to stay focused on upgrade compatibility. We must realize more IPC per watt, and our next-generation architecture will show a 50% improvement of IPC per watt.” So I came away with a somewhat clouded view on IPC, but I did get the distinct impression that AMD’s next-generation architecture would be on par or better than what we have seen with Intel’s Core 2 Duo, which is the low benchmark AMD must shoot for.

Wanting a more defined answer about IPC and where it will be in relation to Intel’s Core 2 Duo architecture, we went back to AMD and asked for exactly that. Gamers know this is going to be of the utmost importance. Phil Hester left us with this:

“With our next-generation architecture we expect to continue our track record of delivering industry-leading performance. When you combine this with 4X4 you change the rules of the game, and provide an enthusiast-class platform that is upgradeable, scaleable and unparalleled in terms of performance.”

Sounds to me that AMD is confident of their position against Intel’s Core 2 Duo when compared with Barcelona.