The Quest for More Processing Power, Part Three: "Multi core of Intel and AMD compared"

Introduction

The Pentium-D dual core Pentium 4 and Opteron 875 dual core are launched. At the end of 2007, a quad core Whitefield CPU will be launched by Intel, and a quad core “K9” of AMD will make a stand against Whitefield. The multi core train has picked up speed and is unstoppable. But what will be the challenges ahead? What are the architectural advantages of the current cores? What will set the different architectures apart? Read on in this third part of The Quest for More Processing Power series.

In case you missed it, in our first article, we explained that dynamic power, power leakage, the memory wall and wire delay have forced CPU designers to rethink the methods that they use to achieve higher performance CPUs.

In Part 2, Tim Sweeney, the leading developer behind the Unreal 3 engine, explained the challenges of multi-threaded development of the next generation of games.

The multi-core future...

In the past 15 years, architectural improvements have made sure that the Pentium 4 issues and retires about 6 times more integer instructions each clock cycle than an Intel 486 could on average. At the same time, the die size would have been 15 times bigger if there were no advancements in silicon process technology, and even those aggressive advancements could not avoid the fact that the Pentium 4 needs almost 20 times as much power.
 
Clock speed increased from 33 MHz to 3800 MHz, so it is clear that clock speed, not extracting more ILP (Instruction Level Parallelism), has been the main reason why a Pentium 4 performs so much better than an i486.

However, the next generation of CPUs will be based on a completely different philosophy. The Xeon MP Version 2007, alias Whitefield, will have 4 cores, and run at speeds at around 2.6 GHz. At that speed, there are reports that it would consume less than 90 Watt. Intel will use its P-m “know-how” to keep the power dissipation so low. Each core is not really a P-m, but it is clear that the pipeline will be shorter than the one of Willamette, the first implementation of the Pentium 4’s Netburst architecture.

AMD’s K9 seems to be a slightly different beast. Andreas Stiller of C’t reported that this Quad core CPU monster would have a TDP of 140 Watt, and run at about 3 GHz.

So, it seems that clock speed will no longer drive performance, but higher IPC and more cores will.