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Topic Title: Need help in deciding on processor.
Topic Summary: Not sure whether to stay Opteron w/HyperTransport or go Nehalem w/QuickPath and Hyperthreading.
Created On: 04/01/2009 02:55 PM
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 04/01/2009 02:55 PM
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pencil_lead
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I am researching to build a workstation for modeling and animation in Autodesk Maya. I am a mid-level user looking for a CPU with lots of power to allow me room to grow. I desperately want to stay AMD and go Opteron, but am now having doubts due to Intel's switch to a NUMA architecture and resurrection of Hyper-threading. Intel fans are now starting to get to me with their arguments for Nehalem processors. How different, really, are HyperTransport and QuickPath from each other, and will hyperthreading really make that big of a difference?

Does anybody have any support in favor of staying Opteron? Any comments, facts, articles, etc. would be appreciated.
 04/01/2009 09:31 PM
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austinbike
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Well, if you price out opteron vs. xeon configurations on most websites you will see 50-100% price premiums for nehalem.

Don't get too fired up about hyperthreading, especially for workstation applications (that may not be that threaded.)

I have seen some nehalem benchmarks where hyperthreading actually slows down the performance. If you look closely on Intel's submissions, they turn OFF Hyperthreading AND Turbo for many of their benchmarks. Why?

If you market a feature as giving you better performance and then you turn it off for a benchmark you are either being dishonest in your marketing claims or sloppy in your benchmarking.

Take your pick.
 04/03/2009 05:06 PM
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pencil_lead
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I did notice that Nehelam Xeons were much more expensive than Opterons, but I just figured that was due to the DDR3 cache and Hyperthreading, although I did not know that Intel turned off Hyperthreading and Turbo for some of their benchmarks. Do you happen to remember where you found these benchmarks, or the programs they were for? And will DDR3/Hyperthreading really make that big of a difference in those programs which are threaded? To not beat around the bush, what I'm getting at is are there any advantages left in having an Opteron based workstation now that Intel has there Nehelam architecture, or is it a "take your pick" sort of thing?
 04/05/2009 10:01 PM
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austinbike
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I don't recall the benchmarks, but I did find this:

http://it.anandtech.com/IT/showdoc.aspx?i=3536&p=9

and

http://it.anandtech.com/IT/showdoc.aspx?i=3536&p=10

This is just a couple of data points, but it does point to the fact that you can't say HT will always increase performance. This was no different than when they did HT circa 2003 and recommended that you turned it off to get better performance from SQL server (google it.)

But think for a second about turbo. Do you need "extra performance" when some cores are sitting idle, or does it make more sense that you need more performance when all of your cores are maxed out (and less likely to have any headroom for increasing the speed)?

There are some great hype features of nehalem, but you have to look deeply into them.

It is not just the processor that is more expensive and cache is relatively cheap to add to processors (it consumes real estate but is far less technical to implement than core or other logic circuits.)

If you go to Dell's website, an apples to apples nehalem to shanghai comparison shows the nehalem is several thousands more - making the price premium 80-100% above the AMD system.
 04/09/2009 05:04 PM
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pencil_lead
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I read the benchmarks and saw what you are talking about. And no, it does not make sense to make some cores work faster than others while some are sitting idle. But from what I understand thus far, the Nehalems currently have the advantage over Opterons, even when considering decreased performance from HT. But I figure that HT would allow me headroom for programs that are threaded, and I can always just turn it off when it hinders performance. Same with Turbo. And I guess I can benefit from the bandwidth from the DDR3 cache/RAM and higher speeds, while Opterons have not yet made released a Hypertransport 3.1 compliant processor. If this sounds not right, let me know.
 04/12/2009 10:18 AM
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austinbike
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OK, a couple of things. If this is for a server, you don't get the benefit of just "turning things off" - it forces a reboot/reconfigure.

This issue with hyperthreading is that there are some apps that take advantage of it, and others that it actually hinders performance.

The biggest issue on nehalem systems is that they cost delta is so huge. More expensive processor, more expensive motherboards, more expensive memory, you get the picture.

The configuration options are limited. You only get the big performance gains if you populate all 3 memory channels. That is 50% more DIMMs, 50% more power being consumed (and DDR-3 actually draws more wattage than DDR-2, by ~1W per DIMM.) While the voltage is lower, the higher speed and higher amperage nets higher wattage.

You only get the 1333 memory speed with 1 DIMM per channel. 2 DIMMs per channel = 1066. 3 DIMMs per channel = 800MHz. Not good. The more memory you add, the slower it gets.

Latency? How about CL=7 and CL=9. Compare that to the CL=5 on DDR-2 and you see that higher latency drives you to lower performance overall. Not good.

The cost of DDR-3, latency and power will all come down. But not until next year, so buying nehalem in 2009 is not so great.

If you go to Dell's site, for instance and configure an apples to apples nehalem vs shanghai system, you see 80-100% price premium.

You can configure a price matched system, but against a 2.7GHz dual Shangahi (2970) with 16GB, the best nehalem to match that price is the 1.86GHz DUAL core nehalem.

Its an interesting product, but in today's economy, overspending for technology is not a great move.

Plus, you have new shanghai models coming out in a few weeks, and istanbul, the 6-core, is close by as well. And istanbul fits into the same platforms as shanghai for the most part, so you get to take advantage of all of the infrastructure benefits of the current platform (and lower costs.)
 04/23/2009 03:29 PM
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pencil_lead
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Forgive my naivety about the hyperthreading issue; I have never used it before and should not have assumed it could just be "turned off." I have been researching DDR2/DDR3 memory, and most people are saying that DDR3 memory does not make that big of an impact just yet--you are right.
Where did you hear about new Shanghai models coming out this year? I can't seem to find anything, and I already know about Istanbul.
 04/28/2009 03:27 PM
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austinbike
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AMD just announced new parts last week:

SE: 3.1GHz
Standard: 2.8GHz, 2.9GHz
HE: 2.4GHz, 2.5GHz
EE: 2.1GHz, 2.3GHz

EE is a new 40W part
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