X4 Ray Tracing - Optimal CPU

[Ian Pellant]

Lew,

The question is:

Will an AMD FX-8150 with 8 cores ray trace quicker than an Intel i7 that has 4 cores?

Cheers.

[lbuttery]

Ian:

not a clue

good luck

Lew

[Ian Pellant]

Lew,

Me neither... I don't know which is quicker.

The test plan ray trace averages about 68 seconds on the i7.

AMD FX8150 still unknown.

Cheers.

[SkagitDesign]

Ok... Here is an answer for you.

AMD FX 8120. Bumped up to 4GHZ, which it is happy to do. That is the way I run it. 1:31 to Ray trace that. (turn off Photon shooting and I get 27 seconds)

So, my opinion. It is a great CPU.

If you want to do 43 seconds, buy the full boat Intel.

My system is new and I have about $1100 USD into the whole thing, less monitors.

Weigh your cost benefit, I guess.

edit...I used to do multiple Ray Trace in que on my old system. I would set up the cameras, then hit "ray trace" on all of them when I walked out the door for the night. Que works just fine. Chief doesn't seem to care how many plans are open, just how many layouts.

Doug explaining how to shut off one core to Ray Trace, allowing the one to work on Chief is pretty cool too. It should work especially well since I have 8 to play with. I will use that.

[Ian Pellant]

Thanks James,

Yes, I ran X4 with 4 copies of the test plan and it queued them up and ran sequentially. All times were the same as the single test run.

The pain is tuning the settings for the ray tracer to get desired image quality. Times go up exponentially and hours or days can elapse before the balance is found. It used to be weeks.

Found a few reviews of the FX8150 that compared it with the i7 2600. Many of the tests indicated that the AMD was significantly slower than the Intel... until the AMD was overclocked to about 4.5GHz (without OC it bumps up to around 4.2GHz). Add water cooling and it will OC to 5GHz or more. 4.5GHz is okay on air cooling.

The CPU pricing is Aus $292 for the FX8150 and $334 for the i7 2600; but the AMD can use more expensive / faster DIMM so the total costs come out about the same.

From the web reviews it seems that most application code (compiled on Visual Studio) will not be optimal for high core count processors. Win 7 doesn't spread loads across cores. That is expected to be improved in Win 8. AMD have 2 cores per module - 8 cores / 4 modules. Intel have 4 cores with hyperthreading to virtualise cores.... at present, Win 7 and most code compilers favor the Intel model.

Single thread code seems to run 50% slower on the AMD compared to the Intel. With Overclocking the AMD comes closer.

In the longer view, AMD may be on the right track.... but Intel seem to have the speed edge today.

Cheers.

[Ian Pellant]

James,

Post script:

Have you tried running several intances of Chief at the same time and seeing if that loads up the cores more effectively?

It's am old Chief trick:
After starting Chief Architect once, start another session while holding down the <Ctrl> key. Then with 2 instances of Chief open, run the ray tracer in each.... halves the overall time?

Hypothesis:
With 8 cores, run 4 sessions of Chief and ray trace 4 plans at the same time.

Cheers.

[marty]

Ian you havent mentioned overclocking on the i7 2600k. I have mine clocked to 3.7 but reviews suggest it will go over 4.5 with suitable cooling.

[Ian Pellant]

Hi Marty,

Darn it.... oc the i7...

I'm using TechBuy (www.techbuy.com.au) as my supplier... they added some new i7 processors yesterday. But they all need really fast RAM to get the most out of them. RAM over 1600 is uncommon and expensive, in Aus. The new Intels seem to be asking for 2100 or even 2400 RAM.... If the i7 needs fast RAM to overclock then it really could be pricey... I dunno.

Web reviews indicated that the AMD with memory faster than 1600 will overclock fine (spent a lot of time parsing the motherboard, memory web sites for the best choices, then trying to find them on TechBuy was tedious).

I just did a 2 session Chief test, running the test plan ray trace simultaneously. Ran fine... but each ray trace took exactly twice as long as running a single session. In other words - no time improvement over running a single session queueing the ray traces conseqeutively.

I expected that since it ran on an old Intel single core, which hyperthreads to pretend it is 2 cores. (Intel: the core count pretender?)

So: now the big question is whether the AMD FX can run multiple sessions of Chief and the ray tracers simultaneously, at no speed loss in each session.... or can Intel do it better?

From what I read on the web reviews, they didn't load up 4 copies of an application and run those simultaneously. Possibly the AMD FX will run applications in its' modules (4 modules, 2 physical cores per module... thread sharing between those 2 cores... 4 virtual computers at the same time?).

If Chief has not been compiled to support multiple instances so each can run in a separate core... Doug: why not?

Cheers.

[marty]

I had a look on line and it seems 4.5Ghz to 5Ghz is easily achievable with the i7 2600k
http://benchmarkreviews.com/index.ph...&limitstart=14

[jpremodeler]

52 seconds raytrace time. I am already searching my next processor. I handle 3 new projects a week, each with anywhere from 18-40 raytrace images per project. anything i can do to speed up the process, I will.

[Ian Pellant]

Marty,

Dare I ask you to run the test plan ray trace on your computer; then overclock it and see what the difference is?

Thanks.

[jpremodeler]

Marty,

Dare I ask you to run the test plan ray trace on your computer; then overclock it and see what the difference is?

Thanks.

I had a tough time at 5.0 keeping stable. I am air cooled, and my ram config only let me use 1 fan on my heat sink. If you can keep the 2600k stable at 5.0 with air, hat's off.

I did not benchmark my pre/post overclock, but it was a decent bump in speed. If I burn the cpu in a year, the time saved is worth it.

[Ian Pellant]

Overclocking....

I'm applying OC to my old P4 3.6GHZ.

It lives in a Shuttle that has a liquid cooled heat pipe system.

Results so far:
No OC 200: 17:16 CPU temp + 0C
OC 210: 16:27 CPU temp +1C
OC 215: 16:03 CPU temp +1C

Becoming interesting. CPU is running at around 3.9GHz and the performance boost is noticeable.

Currently running a test at OC 220 (frequency boost by 10%)... fly or fry?

The CPU normally runs flat out at 71C. Intel throttles it down at around 90C (Those old Prescott processors were designed to run hot). Seems I have a lot more OC headroom.

Cheers.

[jpremodeler]

I run at 71-73 C during raytracing with air

[Ian Pellant]

... went back to the Intel web site and found the white paper for the P4 660 series. (It is 6 years old, after all). It was designed to cut in throttling at over 73C. I'm on the edge.

OC over 4GHz and Chief ray tracer starts failing. It may be CPU temp throttling.

Seems stable at 220 (3.94GHz) which cuts the test ray trace to 15:43. Shaving almost 2 minutes off the time.

Studying the fan speed settings to see if the CPU temp can be brought down a bit.

Cheers