Introduction

"What you have seen is a public demonstration of 4 GHz silicon straight off our manufacturing line. We have positive indications to be able to take Netburst to the 10 GHz space."

"While architectural enhancements are important, Intel intends to continue its lead in raw speed. Otellini demonstrated a new high-frequency mark for processors, running a Pentium 4 processor at 4.7 GHz."

The first assertion was made at IDF Spring 2002, and the second press release was broadcasted after Fall IDF 2002. Fast forward to the beginning of 2004, and we read in the Prescott presentation: "2005-2010: the era of thread level parallelism and multi-core CPU technology. " What happened to "the 10 GHz space"?


Fig 1. "2005-2010: the era of thread level parallelism and multi-core CPU technology ".

The presentation of the new 6xx Prescott even states that Intel is now committed to " Adding value beyond GHz". This sounds like Intel is not interested in clock speeds anymore, let alone 10 GHz CPUs.

Already, the hype is spreading: Dual core CPUs offer a much smoother computing experience; processing power will increase quickly from about 5 Gigaflops to 50 gigaflops and so on. It is almost like higher clock speeds and extracting more ILP (Instruction Level parallelism), which has been researched for decades now, are not important anymore.

At the same time, we are hearing that "Netburst is dead, Tejas is cancelled and AMD's next-generation K9 project is pushed back." Designs built for high clock speeds and IPC (Instructions per Clock) are no longer highly regarded as heroes, but black sheep. They are held responsible for all the sins of the CPU world: exploding power dissipation, diminishing performance increases and exorbitant investments in state of the art fabs to produce these high clock speed chips. A Prescott or Athlon 64 CPU in your system is out of fashion. If you want to be trendy, get a quad core P-m, also known as Whitefield [2], made in India.

To the point

I am exaggerating, of course. A good friend of mine, Chris Rijk, said: "PR departments having no 'middle gears': they either hype something to great lengths, or not at all." Trying to understand what is really going on is the purpose of this article. We are going to take a critical look at what the future CPU architectures have to offer. Is the traditional approach of increasing IPC and clock speed to get better performance doomed? Does multi-core technology overcome the hurdles that were too high for the single-core CPUs? Are multi-core CPUs the best solution for all markets? Will multi-core CPUs make a difference in the desktop and workstation market?

In this first instalment, we explore the problems that the current CPU architectures face. The intention is to evaluate whether the solution proposed by Intel and other manufactures is a long-term solution, one that really solves those problems. We will also investigate one CPU in particular, the Intel Prescott. So, basically there are 4 chapters in this article that will discuss:

  • The problems that CPU architects face today: Wire Delay, Power and the Memory wall.
    Chapter 1 - The brakes on CPU power
  • The reason why Intel and others propose dual core as a solution to these problems.
    Chapter 2 - Why single core CPUs are no longer "cool"
  • Whether or not these problems can be solved without dual core.
    Chapter 3 - Containing the epidemic problems
  • A case study of the Intel Prescott.
    Chapter 4 - The Pentium 4 crash landing

Although Intel is undeniably the industry leader in the CPU market, this doesn't always mean that the solutions proposed are the right ones. For example, remember MMX, which was a technology that should have turned the (x86-based) PC into a multimedia monster. In hindsight, the critics were right. MMX was little more than a marketing stunt to make people upgrade.

The first implementation of hyperthreading on Intel's Foster Xeon (Willamette Xeon) was turned off by default by all OEMs. And hyperpipelined CPUs with 30+ stages turned out to be an impressive, but pretty bad idea.

In other words, not all hypes have turned out to be beneficial for the customer. Millions of customers are still waiting for the rich content on the Internet that is enabled by and runs so much faster on the Netburst architecture...


CHAPTER 1: The brakes on CPU power
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  • Momental - Wednesday, February 09, 2005 - link

    #41, I understood what he meant when he stated that AMD could only be so lucky to have something which was a technological failure, ie: Prescott, sell as well as it has. Even the article clearly summarizes that Prescott in and of itself isn't a piece of junk per se, only that is has no more room for evolution as Intel originally had hoped.

    #36 wasn't saying that it was a flop sales-wise, quite the contrary. The thing has sold like hotcakes!

    I, like many others here, literally got dizzy as I struggled to keep up with all of the technical terminology and mathmetical formulas. My brain is, as of this moment, threatening to strike if I don't get it a better health and retirement plan along with a shorter work week. ;)
    Reply
  • Ivo - Wednesday, February 09, 2005 - link

    1. About the multiprocessing: Of coarse, there are many (important!) applications, which are more than satisfied with the existing mono-CPU performance. Some other will benefit from dual CPUs. Matrix 2CPU+2GPU combinations could be essential e.g. for stereo-visualization. Probably, desktop machines with enhanced voice/image analytical capabilities could require even more sophisticated CPU Matrices. I suppose, the mono- and multi-CPU solutions will coexist in the near future.

    2. About the leakage problem: New materials like SOI are part of the solution. Another part are the new techniques. Let us take a lesson from the nature: our blood-transportation system consists of tiny capillaries and much thicker arteries. Maybe it could make sense to combine 65 nm transistors e.g. in the cash memory and 90 nm transistors in the ALU?
    Reply
  • Noli - Wednesday, February 09, 2005 - link

    "Netburst architecture is very innovative and even genial"

    genius-like?
    If by genial you mean 'having a pleasant or friendly disposition', it sounds weird. It can mean 'conducive to growth' in this context but that's not so intuitive because a) it wasn't and b) at best it was only theoretically genial.

    Presumably it's not genial as in 'of or relating to the chin' :)

    Agree monolithic was confusing but it was the intel dude who said it - I thought it meant 'large single unit' rather than 'old (as in technology)' as in: increasing processing power by increasing the size and complexity of a single core is now not as efficient as strapping two cores together - a duallithic unit :)

    Sorry to be a pedantic twat.
    Reply
  • Xentropy - Wednesday, February 09, 2005 - link

    Some of the verbage in that final chapter makes me wonder how much better Prescott might have done if Intel had just left out everything 64-bit and developed an entirely different processor for 64-bit. Especially since we won't have a mainstream OS that'll even utilize those instructions for another few months, and it's already been about a year since release, they could have easily gotten away with putting 64-bit off for the next project. It's pretty obvious by now even the 32-bit Prescotts have those 64-bit transistors sitting around. Even if not active, they aren't exactly contributing to the power efficiency of the processor.

    I think one big reason Intel thinks dual core will be the savior of even the Prescott line is supposedly dual cores running at 3Ghz only require equivalent power draw to a single core at 3.6Ghz and should be just as fast in some situations (multitasking, at least). Dual core at 85% clockspeed will be slower for gaming, though, so dual core Prescott still won't close the gap with AMD for gaming enthusiasts (98% of this site's readership), and may even represent an even further drop in performance per watt. Here's hoping for Pentium-M on the desktop. :>
    Reply
  • piroroadkill - Wednesday, February 09, 2005 - link

    #36 -- You really didn't read the article and get the point of it. It wasn't a failure from a sales point of view, and this article was not written from a sales point of view, but a technical point of view, and how the Prescott helped in furthering CPU technology.

    Thus, a failure.
    Reply
  • ViRGE - Wednesday, February 09, 2005 - link

    Although I think I sank more than I swam, that was a very good and informative article Johan. I just have one request for a future article since I'm guessing the next one is on multi-core tech: will someone at AT run the full AT benchmark suite against a SMP Xeon machine so that we can get a good idea ahead of time what dual-core performance will be like against single core? My understanding is that the Smithfields aren't going to be doing much else new besides putting 2 cores on one die(i.e. no cache sharing or other new tech), so SMP benchmarks should be fairly close to dual-core benchmarks. Reply
  • Griswold - Wednesday, February 09, 2005 - link

    Point and case as to why the marketing department is the most important (and powerful) part of any highly successful company. It's not the R&D labs who tell you what works and what comes next, it's the PR team. Reply
  • quidpro - Wednesday, February 09, 2005 - link

    Someone needs to make a new Tron movie so I can understand this better. Reply
  • tore - Wednesday, February 09, 2005 - link

    Great article, on page 3 you talk about BJT transistor with a base, collector and emitter, since all modern cpu's use mosfets should you talk about a mosfet with a gate, source and drain? Reply
  • Questar - Wednesday, February 09, 2005 - link

    "The Pentium 4 "Prescott" is, despite its innovative architecture, a failure."


    AMD wishes they had a "failure" that sold like Prescott.


    Reply

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