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Single core vs Dual core

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December 20, 2005 2:57:37 AM

I am getting ready to puchase a new DELL PC (not AMD as I have some Dell store credit and employee discounts to apply). What processor would be the fastest processing for running video compression software? And if so, by how much?

Especially if I am launching multiple (2 or 4) compression jobs at one time?

a. PentiumĀ® 4 Processor 670 with HT Technology (3.80GHz, 800 FSB)
b. PentiumĀ® D Processor 840 Dual Core Technology (3.20GHz, 800FSB)
c. PentiumĀ® Extreme Edition Dual Core w/ HT Tech (3.20GHz, 800FSB)

Straight Ghz would make (a) 16% faster than (b) or (c), but would the dual core actually run two jobs simultaneously if I launched the software twice? If so, theoretically the (c) option would be ~42% faster than (a)

Example:
Job 1 = Job 2 = 100s @ 3.8Ghz, 115s @ 3.2Ghz

Single Core HT runs 100s+100s=200s for two jobs
Dual Core Core HT runs 115s for two jobs
Where 1 - (115/200) = 42.5%

Correct? Am I missing something?

More about : single core dual core

December 20, 2005 4:24:57 AM

Video compression software is multithreaded. In otherwords if you have two cores, a single video will have its encoding spread over 2 cores for added speed. Or if you are running 2 applications, each core will run 1 application or encoding process in parallel. Theoretically, you could encode 2 DVDs at once without them interferring with each other. Of course, in reality the result is far less than that.

You can flip through these charts to compare the processors in encoding tasks.

http://www.tomshardware.com/2005/11/21/the_mother_of_al...

In the Xvid comparison they had, the 840 is fastest at 4:19, then the 670 at 4:51, then the 840EE at 4:54.

The problem with the 840EE, is that while XP can recognize the 2 virtual HTT cores in the 670 are actually 1 physical core, it doesn't know that the 4 virtual cores in the 840EE are actually only 2 physical cores. As such, it sometimes schedules 2 processor heavy tasks on the 2 HTT cores of 1 physical core. The result is of course a performance reduction. Vista is supposed to correct this problem, but in the meantime program manufacturers have to sort it out themselves. Most programs don't hence the low results.

My recommendation is therefore to get the 840. It's much cheaper than the 840EE and in general you get better performance. Sadly I don't think Dell offers the possibility of having DDR2 800 as the added bandwidth and synchronous mode squeeze out a bit more performance, which is important for the 8xx series as the 800MHz FSB is an extreme bottleneck in the case of dual cores.

I don't know how much of a rush you are in. Intel will be releasing the 9xx which will replace the 8xx on December 27. Dell probably won't have systems available until early January though. The benefit of the 9xx is that it runs with only 79% the power and it also has double the cache which should help alleviate the FSB bottleneck somewhat. As well, the 940 will likely be introduced at a lower price point than the current 840 in order to make room for the 950 above. If you really plan on running 4 encoding processes at once then the new 955EE will definitely be for you. Although it still has the core scheduling problem, it can make up for the performance hit by sheer speed at 3.46GHz and its 1066MHz FSB greatly reduces the bottleneck.

If you need a new computer now, you should see if Dell offers one of ATI's new x1xxx series graphics cards. The ATI 5.13 driver is arriving on December 22 allowing these graphics cards to take over a lot of the video encoding processing.

This is only converting to PSP but it handles a variety of formats. It's certainly worth a look.

http://www.anandtech.com/video/showdoc.aspx?i=2645&p=4
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December 20, 2005 6:42:39 PM

I just wanted to take a minute to thank you for taking the time. The information you supplied was very clear.

Thanks again! :p 
December 23, 2005 8:39:43 AM

I would wait for the 900 series. Many users say that dual core P4s have heat and stability issues. Once the P4 gets to a certain temp, it will throttle itself down to 2.8 ghz and that is a total Rip if you ask me. What program are you going to be using? The helium codec from Divx can really increase performance of hyper threaded P4s as well as dual core systems (up to 90%). So if you have a P4, you may be able to live with what you have until the 900 xeries comes out or Dell starts selling AMD CPUs. On another note, my buddy uses a AMD X2 setup to rock and roll. but he only uses one HDD to run two encoding programs at the same time. He had a fairly new SATA HDD and its giving him problems all the time since he started running the programs simultaneously. Many movies had sync problems and other errors. He is planning to get another HDD and add another IDE channel.
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