Intel Dual Core Performance Preview Part II: A Deeper Look
by Anand Lal Shimpi on April 6, 2005 12:23 PM EST- Posted in
- CPUs
Final Words
The point of this article was to present you with the choice that you'll be making, should you decide to upgrade to a new system in the coming months; the choice between very fast single task performance (and to some extent, light multitasking performance) or more responsive, heavy multitasking performance. No one is really exempt from this decision and you'll have to come to the decision based on your own needs.
We've shown the Athlon 64 to have extremely solid single threaded performance. With the exception of our encoding tests, the Athlon 64 really can't be beat when it comes to running a single application.
The tables are turned as soon as multitasking is introduced, where you can't beat the fact that the Pentium D is able to fulfill the needs of more applications running in the background.
So, the question quickly becomes, how heavy of a multitasker are you? If you're primarily a gamer and you find your gaming performance gets bogged down at all by the tasks you're running in the background, then dual core will most likely outweigh the benefits of a strong single core CPU. If not, then your answer is clear: go for the faster single core.
For encoding performance, you still can't beat the Pentium D. Even a dual core Athlon 64 isn't going to help enough in that area.
To characterize all other non-gaming, non-encoding performance is extremely difficult. For the most part, if you're doing a lot of things at the same time or if you have a lot of applications eating up CPU time - you're better off with the Pentium D. If you are a much cleaner operator and don't have all that much going on, then a single core CPU will still be your best bet; and what better single core to have than the Athlon 64.
The surprise here is the impact of NCQ on multitasking performance. The difference in two of our tests was not only measurable, but also quite noticeable in real world usage. Given that NCQ is quickly becoming a "free" feature of new hard drives, it's a feature that we'd strongly recommend to have in your next system. It doesn't improve performance across the board, but it doesn't hurt things and when it does work, it works extremely well.
With all this excitement, we still have to keep ourselves grounded in the thought that dual core isn't here yet; it's still as much as two months away. For AMD, as we've known all along, the wait is going to be a bit longer on the desktop. The workstation and server markets will be serviced by AMD first, and we will have a look at workstation/server dual core performance as soon as AMD launches those parts. It's looking like, at least on the desktop, if you want dual core at a reasonable price point, your only option will be Intel. But the prospect of more affordable dual core chips out of AMD in 2006 is quite exciting as well.
A dual core Athlon 64 solves a lot of our dilemmas simply because you get stronger single threaded performance than the Pentium D (in everything but encoding) while also getting the multitasking benefits of dual core.
For Intel, the Pentium D is a saving grace - it's the first time that we've been interested in any processor based on the Prescott core. It's also perfect timing; if it weren't for the Pentium D, we'd have no interest in the Intel 945 and 955 chipsets, and definitely not in NVIDIA's new nForce4 SLI Intel Edition product. With that said, it should be pretty clear what our next article in this series will be...
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BoBOh - Monday, April 11, 2005 - link
Where are the code compile tests. We're not all gamers, some are software developers! :)BoB
NightCrawler - Saturday, April 9, 2005 - link
Dual core Athlon 64's in June ?fitten - Saturday, April 9, 2005 - link
- also, there should be (SMT) after simultaneous multi-threading in the quote from the paper on the IBM site.fitten - Saturday, April 9, 2005 - link
- quote should be in front of "Scalable not after.fitten - Saturday, April 9, 2005 - link
a) By definition, Intel's implementation must be different than IBM's or anyone elses' because the CPUs aren't implemented the same. Not only do they implement different ISAs, but the entire architectures are different... different number of registers, different ISA, different designs.2) Intel's definition of HyperThreading: http://www.intel.com/technology/hyperthread/
D) This paper http://domino.watson.ibm.com/acas/w3www_acas.nsf/i...$FILE/heinrich.pdf , found on IBM's site by searching, is entitled Scalable "Multi-threaded Multiprocessor Architectures". The first paragraph states: "The former [hardware multi-threading], in the form of hyper-threading (HT) or simultaneous multi-threading, appears in the Intel Xeon and Pentium 4, and the IBM POWER5."
Reflex - Friday, April 8, 2005 - link
Well first off, I am not going to do everyone's homework on this, the info is out there, you all have Google. If you ask a IBM engineer if what Intel is doing is the same as what they are doing, or even if it is really SMT, they would tell you flat out that it is not and they fullfill completely different needs in their products and are implemented completely different. Your definition seems to be that the hardware can accept two threads, therefore it is SMT. That is a VERY simplisitic definition of what SMT is, when there are actually many variations on the concept(HT is a variation, but it is not what most CPU engineers consider actual SMT).One of the primary issues here is that HT does not actually allow two simultanious threads, it is more of a enhanced thread scheduler that attempts to fill unused units with jobs that are pending. A true SMT CPU is actually architecturally able to execute two simultanious threads, its not just filling in idle parts of the pipeline with something to do(highly parallel designs). There is a ton of info on this, if you care I suggest you do the research yourself, I don't have the time(and in some ways the expertise) to write a lengthy article on the topic.
Alternatly, you can just buy into the marketing I suppose, its no skin off my teeth.
fitten - Friday, April 8, 2005 - link
I was going to comment on the phrase "true SMT" above. I'm wondering if this comes from the same lines of thought as the "true dual-core" arguments.Anyway, "HyperThreading" (HT) is just Intel marketing terminology for Symmetric MultiThreading (SMT). They are one and the same, with the same design goals... to more effectively utilize core resources by keeping the resources more busy instead of sitting around idle, particularly at the time granularity of cache misses and/or latencies.
defter - Friday, April 8, 2005 - link
#93 "Intel has labeled it as SMT, however there is another name for what they are doing(that I cannot remember at the moment). What they are calling SMT is nowhere even close to solutions like Power."Well please tell us the exact definition of SMT and the difference between the multithreading in Power and P4?
"That aside, the implementation Intel has chosen is designed to make up for inefficiencies in the Prescott pipeline"
In Prescott pipeline? Why did the HT exist in Northwood based Xeons then? Of course the SMT is designed to reduce inefficiencies in the pipeline. If the CPU can utilize most of its resources when running a single thread there isn't a point of implementing SMT.
saratoga - Friday, April 8, 2005 - link
#93: Intel labeled SMT Hyperthreading. It is effectively the same as what the newer Power processors do (make one core two threads wide).It also was not designed for Prescott, rather it was included in the P7 core from the beginning. For this reason it was available on P4s prior to Prescott.
saratoga - Friday, April 8, 2005 - link
#80:HT improves the utilization of execution resources. Its not a bandaid, its a design choice. In some cases it can be used to compensate for some other weakness, in others it can simply be to increase throughput on multithreaded workloads.
Sun and IBM use it because they build server systems and SMT makes a large difference in traditional server loads.
Intel uses it because they realized it would work well with the P4. I don't know why AMD does not use it. Probably because they don't think the Athlon has enough unused hardware on typical loads to justify the extra transistors. Or maybe just because the Athlon was not designed with it in mind and they can't justify redoing the whole thing to add a single feature. Or maybe a combination of the two.