HyperTransport and Opteron/Athlon64 Overclocking

The first question many will have about our efforts to look at how Athlon64 will perform is how we can possibly compare an overclocked Opteron to a chip that is not overclocked. In the case of the Opteron, the comparison is more accurate than you might first think.

In normal setups (e.g. Athlon/P4), the CPU gets its clock from the FSB clock and multiplies it by the “clock multiplier” to determine how fast its internal clock should be. With a 16x multiplier, when the external clock ticks once, the CPU ticks 16 times. However, with the Athlon 64/Opteron, there is no FSB, so the CPU must get its clock from somewhere. It doesn't produce it internally; instead, it derives it from the native HT (HyperTransport) frequency, which is 200MHz, but because of the bus' nature, it runs at an effective 800MHz.

So, for our 1.8GHz Opteron 144, the multiplier is 9x, which is why raising the HT frequency to 222MHz increases the clock speed to around 2GHz. But we are increasing the HyperTransport clock in our overclocking, and not a FSB clock, which does not exist on Opteron/Athlon64. In real terms, this means our CPU overclocking has a significant impact on Performance, but it is unlikely that our increase in memory speed will have nearly as much impact on performance. Since we are nowhere near saturating the Hypertransport bus at 200 (effective 800), increasing HyperTransport to 222 (888) will not likely have much, if any, impact on overall performance. Our performance improvements, with Opteron/Athlon64, are mainly coming from increase in CPU clock — much more so than on the Pentium 4 or Athlon architectures.

Obviously, the PCI bus operates at a different frequency than the HT bus than the CPU, but they all operate based on multiples of each other, and are all derived from the HyperTransport clock.

nVidia nForce3 Chipset Performance Test Configuration
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  • Anonymous User - Saturday, October 25, 2003 - link

    I found it difficult to compare products because of the way the descriptions of processors and components were laid out.
  • Anonymous User - Wednesday, September 24, 2003 - link

    Well for any Intel posters you can avert your eyes. I've recently been doing some shopping to piece together a new system for myself. I'd decided on AMD since their systems have always been good to me and cuz ..screw the big boys.
    Anyways I've been out of the hardware game for a while and the 64bit cpu is really interesting for me. I do a lot of 3d animation and video editing. SO my question is this 1)is there a trustworthy, compatible Mobo out there now that will work with amd64 that I could build now and upgrade up to later? 2)Is there another solution from the current 32bit amd processors that could give me all my needs (gaming, animation, editing, etc..)? or should I just wait for 64 to come out (which I really REALLY need to build a pc fast)??
    I'm open to any and all suggestions :)
  • Anonymous User - Saturday, September 13, 2003 - link

    Speaking of AMD vs Intel & the Sysmark 2002 cheating allegation, just wait until XP-2003 for AMD comes out and you install Sysmark 2002. Anyone with half a brain will understand what Intel & Bapco did to stack the deck when the system reboots after install. Very revealing.

    Remember this.
  • Anonymous User - Saturday, September 13, 2003 - link

    Hmmm, talking about stocks. Actually in the last 3 months, AMD also doubled its price. So, if you own either Intel or AMD stock, you will have gain a lot of money. The stock increase occurs because investor expect that the chip sector is improving this year, i.e. there is an increase in the demand of cpus.
  • Anonymous User - Saturday, September 13, 2003 - link

    I don't know if anyone is considering this but don't you think the prices for a processor are becoming a tad bit HIGH!? As it stands in order for me to get a piece of this new technology(Athlon 64 and its motherboards) I would have to cough up $1000+! $1000 for a cpu and motherboard!!! For companies that want its customers to flock to thier stuff when they release them that is TRULY not encouraging anyone to go out there and buy at all. As it stands I don't think a lot of people will be able to buy this thing right off the back no matter how bad they want it. The Opteron 940 is higher than my HOUSE NOTE right now for my 2-story home. The AthlonFX isn't any better. Right now Directron.com has the Athlon64 up for pre-order at the price $489. Ladies and gentleman that is a whole f***ing check for most people. I really do think that the Athlon64 and the Opteron are an advancement and a powerful one but could they please stop raising these prices?
  • Anonymous User - Friday, September 12, 2003 - link

    Please stop repeating the same questions...

    The only thing I wanted to point out is that the drivers that are recompiled for the Athlon 64 are going to make a difference more than anything else discussed in this comment section.

    As for this Pentium 4 arguement, the P4 3.2 GHz 800MHz is $613. That is about $200 more expensive than the Opteron 242 and $150 more thank an Opteron 144. The MBs will become cheaper due to the lack of a Northbridge and ease of design. $130-140 is the price I expect the Nforce 3 boards to sell.

    Whatever you want is what CPU you should use. Just know that if you buy an Opteron or Athlon 64, that every driver update is going to get you more speed. Every update patch to games will get you more speed. And you have the ability to go to Windows XP 64 when it is finished and run even faster. Over time, you may have a 20% or more improvement in speed. If it doesn't, then you have a really fast CPU at 1.8 GHz running less than 39c while benchmarking.

    It will be a nice laptop.


  • Anonymous User - Thursday, September 11, 2003 - link

    The testing methology is flawed here.

    You have an Opteron that is OVERCLOCKED to 222MHz HT bus/RAM, versus a stock standard 3GHz P4 (why no 3.2GHz?)

    It's like comparing a 2.8C @ 3.2GHz and comparing it to a 1.8GHz Opteron. I'm sure that would create an uproar of 'Intel BIAS!' type of comments. ;-)

    Don't get me wrong, Opteron/A64 is an impressive processor, but the review would've been much more credible had Anandtech reviewed a stock 2GHz Opteron vs a 3.2GHz P4, instead of an overclocked Opteron 1.8GHz @ 2GHz with faster HT bus and RAM, compared to a 3GHz P4, which isn't even the fastest available.
  • Anonymous User - Wednesday, September 10, 2003 - link

    I'm a noob and I have a question. I'm not understanding how us gamers will be able to play our games (like bf1942) when these processors come out if there isn't a 64 bit OS out for us to run. Can anyone clear this up for me?
  • Anonymous User - Wednesday, September 10, 2003 - link

    Considering this was testing its performance on a 32bit OS, I cannot wait to see how well it fairs in a true 64bit enviroment!

    I say....each to their own preference. Be glad you have the option to choose Intel or AMD and that their competion produces a less noticable strain on our pockets!

    **Ignorance is the weapon weilded by the man with closed eyes!**
  • Anonymous User - Monday, September 8, 2003 - link

    #18, some Xeon's (not XeNon) have 1 meg L3, as well as 512 K L2 like any nortwhood. The L3 is inclusive however, which basically means that data stored in L2 is also duplicated in L3 to allow faster chaches. This results in a "net" cache size of 1 Mb, not 1.5.

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