Phenom or i7 for Terragen rendering?

[reck]

I'll probably be building a new PC at some point and thought I'd take a look at the sort of prices I'm going to be paying for the CPU. The last two system I've built have had intel chips inside but today I took a look at the AMD Phenom II X6. I suppose it's intel rival is the Core i7 960 and from a price\performance point of view it seems the Phenom wipes the floor with the i7.

The intel chip is a lot more expensive and only seems to offer a marginal increase in speed over the Phenom and the Intel only has 4 cores compared to the Phenoms 6.

Is the i7 really worth an extra £239 when it's passmark score is only 184 points faster than the AMD?

From a Terragen point of view do you think there would be much difference in rendering speed? The intel i7 has hyper-threading so would a 4 core cpu running with 8 threads render much faster than a true 6 core cpu?

These are the specs I'm basing my information on.

Intel Core i7 960 @ 3.20Ghz – 4 cores
Passmark score = 6688
Price = £475.99


AMD Phenom II X6 1090T @ 3.20Ghz – 6 cores
Passmark score = 6504
Price = £236.99 (on sale currently for £230.23)

Prices  are from Overclockers.co.uk


I know we have users using intel i7's, do we have any Phenom II x6 users who would be willing to offer their experience?

[cyphyr]

I'm interested in this too. I'd add however that the i7's support virtualisation (I think that's the right word, used to be called hyperthreading)  so you get the rendering power of 8 cores, not 4. Although the Phenom are true individual cores I don't "think" that they support virtualisation.

Richard

[reck]

Thought i'd pull up the passmarks for most of the i7 range and compare speed and prices with the Phenom II x6.

The table below is sorted by passmark speed, slowest to fastest.

i7 920 - 2.66Ghz - £184.99
passmark = 5575

I7 930 – 2.8Ghz  -  £229.99
passmark = 5847

I7 860 – 2.8Ghz  – £244.99
passmark = 5525

I7 870 -2.93Ghz  - £419.99
passmark = 5866

Phenom II x6 1090T – 3.2Ghz -  £236.99
passmark = 6504

I7 – 960 – 3.2Ghz  -£475.99
passmark = 6688

It's interesting to see that compared to the Intel i7 860 the Phenom has a faster clock speed, 2 more cores and consequently a high passmark yet costs less money than the i7 860.

[Henry Blewer]

The Intel chips have a feature called 'scaling'. This increases the number of cores utilized by a multi-thread program, and also calls on the hyper-threading capabilities of each core as needed. This results in increased voltage use and heat.
The AMD X6 is not capable of this to such an extent. It will draw on more cores during heavy usage. I am not sure about the hyper-threading of the AMD.
I am leaning towards an X6 AMD CPU because of the cost. I can afford more memory by going the AMD route. I can also get a faster motherboard. Eventually, if AMD maintains the pin configuration of the CPU, the CPU can be upgraded to a faster unit when they are available. This may be all wrong, but it is how I understand the differences and capabilities of each.

[reck]

The Intel chips have a feature called 'scaling'. This increases the number of cores utilized by a multi-thread program, and also calls on the hyper-threading capabilities of each core as needed.

AMD has this as well, only they call it "turbo core". It sounds like intel's version is better though in that it can shut down cores while AMD,s only under clocks the cores. I'm not sure about hyper-threading on the AMD either, i've not read anything about it so i'm thinking that it doesn't have it.

http://www.anandtech.com/show/3674/amds-sixcore-phenom-ii-x6-1090t-1055t-reviewed/2

I don't think the difference between "turbo core" and "scaling" is anything to worry about, but hyper-threading is a nice feature, just depends if a 4 core hyper-threading cpu is better than a 6 core non-hyperthreded cpu for rendering.

If there is a big difference in speed i'd consider paying out the extra for intel, but if there's not much difference it seems the AMD chip is the better choice leaving you with £230+ to spend on other goodies.

[Henry Blewer]

Interesting. From the article, I would think the Intel CPU would be more consistent with the clock speed across all cores and applications. I think for a user this would be a more consistent work environment.

With the amount of multitasking I do on my P4 HT. I now think the Intel i7 is probably a better choice.

[reck]

To be honest I wasn't even considering an AMD chip, I just had decide which i7 to get. But now I am seriously considering it as at least an option.

Reading that anandtech article their opinion is that if you use applications that take advantage of multiple cores (Terragen\Blender etc) the AMD chip is the one to get, for a more general purpose system the i7 chip is the one to get.

I'm still undecided, now that i've see the spec and especially the price of the Phenom II complete with 6 cores it makes the i7 chips look very expensive. I think more research is needed, i'd love to hear from Terragen users who have i7's and especially Phenom.

[Oshyan]

The i7's dynamic overclocking feature is called "Turbo Boost" not "scaling". Hyperthreading is still called Hyperthreading (Intel's term for what is really simultaneous multithreading). "Virtualization" is the ability to create "virtual machines", a form of whole system hardware emulation, to effectively allow running multiple separate "systems" off one set of system hardware. So it's unrelated, and probably unnecessary for Reck's needs, or most TG'ers for that matter. Nonetheless the Phenom II X6 should support a form of hardware virtualization anyway.

As to the original question, Passmark is a fairly simplistic test, or more accurately it is a theoretical rather than real-world benchmark. It's not throwing real workloads at the CPU, they're abstract mathematical tests to assess theoretical performance. Real-world workloads are much more telling as they give you a better idea of how issues like contention, memory bandwidth, cache sizes, etc. can affect your actual software use, or at least something like it. So seeing some benchmarks of a multithreaded rendering application on both CPUs is pretty important to get a real idea.

So for example:
http://www.tomshardware.co.uk/charts/2009-desktop-cpu-charts-update-1/3DS-Max-2009,1380.html
Notice the i7 920 (which has similar performance to the 860 which is not on that chart) is ahead of the Phenom II X6 at 3.2Ghz.
Another take here, where the X6 does a bit better:
http://www.tomshardware.com/reviews/amd-phenom-ii-x6-1090t-890fx,2613-8.html
And one with a wider variety of tested apps:
http://www.anandtech.com/show/3674/amds-sixcore-phenom-ii-x6-1090t-1055t-reviewed/7
Mixed results for the X6.

In general where Terragen is concerned, i7's do seem to have the edge, and while there are no 6 core Phenom II results at the TG2 benchmark page, you can potentially extrapolate based just on comparative clock speeds and number of cores:
http://3dspeedmachine.com/?page=3&scene=47
Hopefully we'll get some Phenom II X6 results soon.

All things considered I think it's pretty clear the Phenom has the price/performance edge. However you can go for an i7 860 rather than 960 and be trading places with the Phenom depending on the benchmark you try, and it'll perform better in single-threaded tasks to be sure. On Newegg the 860 just edges out the X6 for price, though total system cost would be the same or higher since i7 motherboards are more expensive.

There's also power use to consider, as that can give you a nice bill at the end of the month if you run them constantly (as I do). 125W for the Phenom vs. 95W for the i7 860.

Anyway, I bought my i7's before the X6 was out, but I'm not sure I'd decide differently now. It's important to remember that it's not clock-for-clock parity; the i7's are higher performing per clock. You need to look at the right benchmarks and compare performance-for-performance. When you do that the prices are a lot closer.

- Oshyan

[reck]

Very informative post Oshyan, thanks.

I think just looking at the passmark scores is misleading because it makes the i7's look very overpriced. But looking at the rendering benchmarks you posted I can that the price/performance isn't as bad as I first though. After reading your post and looking at the links I think that an i7 is the way to go.

But. I've just read this article which says that intel's next generation of cpu, Sandy Bridge, is coming out sooner than expected, within months. If this is the case then I think it makes sense to hold off for a while until after release to how the Sandy Bridge affects prices. I would assume the SB chips will be very expensive to begin with but may lead to price reductions on the i7 chips.

http://www.pcworld.com/article/201041/intel_to_ramp_up_sandy_bridge_faster_than_expected.html

[Oshyan]

Cool, I hadn't heard about SB coming out so soon. You may be right about price drops, then again Intel has a habit of introducing such chips at the high end and then simply retiring the high-end competition, leaving the mid and low range at roughly the same price, and not competing with those existing offerings. In other words they may bring out SB CPU #1 in their "Extreme" range priced at $999 or something, and leave the i7 860, etc. where they are. Basically like swapping out the 980 for the next generation.

Also it looks like it won't be out until maybe the end of the year still, and any impact from it wouldn't be until early 2011 in that case (most likely). Not sure what I'd do if I was in the market now, hehe. The i7's are still awfully good right now.

Having said that, the benchmarks do look interesting in some cases. Just wish we knew what CPU models would be released first. One thing is for certain, if you're doing AES encryption you'll want one.
http://hwbot.org/blog/wp-content//S91.png
I'm not entirely clear what each benchmark represents or the comparative value for an i7 of similar clock speed, but:
http://hwbot.org/article/newsflash/639_sandy_bridge_benchmark_results_leaked
Assuming those are real, there are some pretty amazing numbers... And if a 2.5Ghz chip will actually debut at launch, well that ought to be in the mid range and therefore affordable!

- Oshyan