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View Full Version : Interesting note on render times w/Pentium-M

rnb2
09-14-2003, 10:24 PM
Haven't done much testing over the last few days, as I've been busy configuring the new Dell Latitude D800 that just arrived for me at work (my "day job" is IT for a group of non-profits). It sports a 1.6Ghz Pentium M processor, 512mb of RAM, 30Gb HD, WUXGA+ screen (1920x1600, 15.4" wide-aspect) and a 64mb GeForce4 4200 Go graphics chip. Yes, I speced the machine hoping to take advantage of any "down-time" at work to do something, well, creative.

So, I got LW 7.5 and messiah:studio Rev9b loaded and configured, and both seem to run quite well on it. It appears that the OpenGL performance is a bit slower than my home rig (an Athlon 2100+ with 1Gb of RAM and a GeForce4 4200), but nothing dramatic, and completely useable.

I hadn't tried a render test until today, however, and I was shocked. No, wait, make that *****SHOCKED******. While it renders a bit faster in LW (scene that took 10m40s on the Athlon took 8m30s on the Pentium M), the speed difference in messiah:render is dramatic, to say the least - so far, scenes are rendering anywhere from 2.5-3 times as fast.

For instance, a scene with one metanurbed character, an area light (direct illumination only, no radiosity), floor, and UV colormap rendered in 2m32s on the Athlon, and rendered in 49s on the Pentium M. The same scene with Monte Carlo radiosity clocked in at over 13 minutes on the Athlon, and at 4m55s on the Pentium M. All benchmarks were run with the Dell running on its AC adapter - not sure if performance will be similar on battery power, and if that can be tweaked via system power settings.

So, a question for pmG (or anybody else who might know) - is this performance due primarily to the large L2 cache the Pentium-M is running (1mb)? Or is there something else going on here? I know that LW takes advantage of Intel's SSE2 instructions, so I expected a performance boost in Lightwave (and got about 15% in my test), but I'm not aware of messiah operating in the same fashion. The two renderers are fundamentally different, of course, with Lightwave using a Zbuffer technique while messiah uses scanline, and I'm not sure how much effect that has on this test.

So, anybody know the scoop on this? Needless to say, I'm happy that I now have a very serviceable animation and render box that I can carry around with me.

Rick
Qslugs
09-15-2003, 05:43 AM
Probabaly has a bunch to do with the cache, however I am getting what I consider descent times with my dual 1.7 xeon machine. Thoes chips however only have 256k on each chip. Could just be that the app is not optimmized to run on amd hardware.

Also that sounds like a kick ass portable you got there.
chikega
09-15-2003, 11:53 AM
this is an email that my twin brother sent me concerning this - he works at Cisco Systems:

"Here's the reason why the Centrino Mobile P4 is faster (not to be confused
with the regular Mobile P4) - the Centrino has 1MB of Secondary L2 "on-die"
Cache. Normal P4s have 512KB of Secondary Cache. 512KB has been the standard
size since the old PII's except that the 512KB cache was on the package
(remember the old Slot 1s?). The 512KB cache moved from the package to
the "die" with the advent of the PIIIs. It's very unusual that a mobile
processor gets the larger secondary cache vs. their workstation class CPUs.

http://www.intel.com/products/mobiletechnology/docs/performance_brief.pdf?iid=ipp_perf+perf_brief&


Even the latest desktop P4, the 3.2Ghz (800mhz bus) only has 512KB of
secondary cache. I can only imagine if that was bumped up to 1MB.

http://www.intel.com/products/compare/index.htm?iid=ipp_dlc_procp4p+tools_compare&

Cheers,
Gerry
"
Wegg
09-15-2003, 05:17 PM
Yikes.

I have an entire room full of Athlons here at Eggington. . .

Can anyone else confirm this dramatic speed increase in Intel chips?
rnb2
09-15-2003, 05:44 PM
Wegg,

As I noted, the render speed difference in Lightwave is notable (between 15-20% on one test scene, so YMMV a lot), but not overly dramatic. I've always heard that the P4 FP unit was a bit weak compared to the Athlon, so while the clock speed would be higher, you wouldn't see as much of a difference as you might think.

My gut feeling is that the Pentium-M performance is partially due to the design of the chip (it does more with each clock cycle to save power) and partially due to the 1mb L2 cache (which will apparently grow to 2mb on the 2nd gen Pentium-M that is due late '03/early '04).

The thing you need to balance is, of course, rendering-muscle-per-dollar, and I think the Athlon would still win that battle. I don't think you're likely to see the same sort of speed on straight P4s (especially not the ones you can buy for cheap these days), so the Athlon should still be the best value for rendering. You can build Athlon boxes like my home machine (with cheap video if they're just rendering) for probably $300-400 these days, so you can make it up on volume :)

BTW, are you guys planning on going to messiah:render? The render speed difference there is very dramatic, but I still think you'd get better value-for-money out of Athlon boxes in the end. I'm just happy because I've got a portable animation/rendering box that I didn't have to pay for :) Pretty radiosity renders are a lot less painful at 5 minutes per frame than at 15.............

Rick
Wegg
09-15-2003, 05:49 PM
We like Sasquatch, and Darktree, and are looking into G2 and Shadow Designer so. . . I'm not sure we will be switching to Messiah:Studio's renderer any time soon.

But I like doing little tests every now and then to get a feel for it.
TRick
09-15-2003, 07:46 PM
[i]...not sure if performance will be similar on battery power, and if that can be tweaked via system power settings....[/B]

If you set Quickset to max.performance you will get the same power/speed as with AC...I let it render with only the primary 7200 batt. (LW scene with volumetrics and every raytrace parameters on, which garantees a full 100% processor use) and after 50 minutes he started begging for AC...so use it wisely...
chikega
09-16-2003, 03:20 AM
Originally posted by Wegg
We like Sasquatch, and Darktree, and are looking into G2 and Shadow Designer so. . . I'm not sure we will be switching to Messiah:Studio's renderer any time soon.

But I like doing little tests every now and then to get a feel for it.

I know what you mean, I have so heavily invested in the same plugins for LW it would be very difficult to make a transition ... Sasquatch, Darktree 2.5, G2, IFW2 textures, etc...
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