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SLI bottleneck

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December 12, 2010 12:11:20 AM

will an Athlon II x4 640 3.0 GHz bottleneck a GTX 460 SLI setup.


More about : sli bottleneck

a b à CPUs
December 12, 2010 12:15:27 AM

A little, try overclocking to around 3.4ghz
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December 12, 2010 2:17:25 AM

so if I overclock it over 3.4 ghz, will it run fine or still be a bottleneck.


the reason why I am asking you this is I saw a review somewhere on toms hardware forums of Athlon II x3 440 compared to the rest of the cpu's and there was a lot of performance difference compared to the others which included the phenoms and the i7's on an SLI setup.
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December 12, 2010 11:23:17 AM

3.4 is a guess you'll have to do some testing. That chip is speedy enough to handle sli with some overclocking. Make sure you watch your temperatures and voltagea if you are overclocking.
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a b à CPUs
December 12, 2010 11:35:23 AM

No matter how much? He'll have to give it a healthy overclock to 3.4 or higher, But that should run the two cards.
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a b à CPUs
December 12, 2010 11:42:24 AM

Even pushing 4.0Ghz?
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a c 115 à CPUs
December 12, 2010 11:48:09 AM

If we knew what motherboard you were using (along with your RAMs) you will get a bit better advice and suggestions. Your rez and games you play would help, too.

I imagine your frame rates are very good right now. If you feel like you are being held back in any way or want better frame rates, you will get a nice bump by overclocking the processor and memory controller -- by raising the system clock and making a few adjustments in the BIOS.

Otherwise, you probably shouldn't worry about it.
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a c 103 à CPUs
December 12, 2010 1:07:24 PM

The resolution you are using will make a big difference to the bottleneck but what ever it is its a very powerful GPU setup with a weak (but very good value) CPU
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a b à CPUs
December 12, 2010 1:53:19 PM

Quote:
^Dude of course it will run two cards.But it will badly bottleneck.


Could you provide some proof of that please, hard numbers from reputable sources only by the way.
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a b à CPUs
December 12, 2010 2:44:27 PM

The biggest differences between the Athlon II and Phenom II cores is the amount of cache and the speed of the HT links to the mainboard (the Athlon II uses HT 2.0, while Phenom cores use HT 3.0). What may be slowing down the Athlon II is a combination thereof. As more and more operations saturate the HT channels going in and out of the processor, the processor will start caching process results and then fetching the results whenever it comes across an operation that already exists in cache.

Since the Athlon II has a smaller cache, there is a point where it has to start accessing the main memory instead of the cache, and do so on a slower HT link. Thus, the Athlon II will find itself very quickly becoming i/o bound, much earlier than Phenom II cores, which have a bigger cache and a faster HT link to the memory and chipset.

Dipankar is right that the graphics will bottleneck well before the GPU is truly taxed, compared to other systems with a similar setup. Hence, the reason why others suggested overclocking the CPU. This gives the Athlon II a much better chance at keeping up with the data coming in. If this doesn't satisfy the OP, then he can check to see if his mainboard supports any of the Phenom II processors (some of the NForce chipsets do, some don't, depending on the manufacturer) and go that route for an upgrade.
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a c 115 à CPUs
December 12, 2010 4:01:35 PM

Houndsteeth said:
The biggest differences between the Athlon II and Phenom II cores is the amount of cache and the speed of the HT links to the mainboard (the Athlon II uses HT 2.0, while Phenom cores use HT 3.0). What may be slowing down the Athlon II is a combination thereof. As more and more operations saturate the HT channels going in and out of the processor, the processor will start caching process results and then fetching the results whenever it comes across an operation that already exists in cache.

Since the Athlon II has a smaller cache, there is a point where it has to start accessing the main memory instead of the cache, and do so on a slower HT link. Thus, the Athlon II will find itself very quickly becoming i/o bound, much earlier than Phenom II cores, which have a bigger cache and a faster HT link to the memory and chipset.

Dipankar is right that the graphics will bottleneck well before the GPU is truly taxed, compared to other systems with a similar setup. Hence, the reason why others suggested overclocking the CPU. This gives the Athlon II a much better chance at keeping up with the data coming in. If this doesn't satisfy the OP, then he can check to see if his mainboard supports any of the Phenom II processors (some of the NForce chipsets do, some don't, depending on the manufacturer) and go that route for an upgrade.


That's all nice ... but it's pretty much a load of crap.

AthlonII Lack of L3 General Rule of Thumb: 5-10% less performance than comparably clocked PhII

You don't know what HT is, do you? Or even know the difference between HT2 & HT3? And - LOL - The AthlonII and PhenomII each use the same HT, anyway, so whatever point you are trying to make is pure garbage.

As with the PhII, with the AthlonII in memory intensive applications (and gaming), for each 10% the IMC/NB speed is increased, bandwidth is increased 3-4% and latency is reduced 3-4%. Stock is 2000MHz - 2400MHz is a 'slam dunk' without touching the volts. Beyond 3000MHz is not uncommon with enthusiasts.

At 2400MHz IMC/NB the AthlonII will perform in a quite similar fashion to a comparably cpu-clocked Phenom II.

And btw, I/O (even in over-clocked operation) will not exceed 50% of HT2, much less HT3.

And finally: If the OP has 2x460s he is running an NF chipset. Some older boards, exactly like AMD, also, may be limited to 95w, but dang that AMD backward socket compatibility ?? Is that what you are saying here ?


Quote:
The Athlon x4 lacks level 3 cache which is basically a small amount of very fast memory on the cpu itself. This is the main difference between current Athlons and Phenom II's and it means that instead of being able to keep vital parts of data on the CPU it will have to send it back and forth to the slower ram. There aren't many games that actually utilize 4 cores all at once, most modern games will only use 2 (even GTA4 will run optimally with 3 cores although you may need to turn clip recording off) so If you can't quite stretch to a quad core Phenom II then a dual or triple core version would serve your needs just as well.

www.anandtech.com/bench/Product/188?vs=109
That benchmark shows how much athlon bottlenecks a 5870.And when more powerful gpu setup will be used amount of bottlenecking will only increase.


This is piled even higher. The ignorance is strong on this one, and the link is some type of bait and switch. A listing of benchmarks with a few games thrown in? That's a bad joke and in no way backs up the premise of a "...severe bottleneck..."

The higher the resolutions, the less the lack of L3 will have any significant impact. If you force a lower resolution (which begs the question, "Why would you with 2x460s?") to prove a 10% bottleneck between a PhII and AthlonII, what exactly have you accomplished, again?







Quote:
...Overall, the main performance differentiator between the Athlon II X4 and the Phenom II X4 is clock speed. A simple 200 MHz increase for the Athlon II X4 would probably match the performance of a Phenom II X4, despite its large 6MB L3 cache....


From Tom's: Athlon II Or Phenom II: Does Your CPU Need L3 Cache?



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December 13, 2010 2:22:55 AM

thank you for providing such a brief and a clear explanation. I understood it very well.

let me tell you that I have an ASUS M4N75TD sli motherboard.

I would be gaming at 1680*1050 resolution.


so please tell me if I should go with an Athlon II x4 640 or a Phenom II x3 720 or is it mandatory to get a Phenom II x4 itself.
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a c 115 à CPUs
December 13, 2010 1:10:46 PM

irfan88 said:
thank you for providing such a brief and a clear explanation. I understood it very well.

let me tell you that I have an ASUS M4N75TD sli motherboard.

I would be gaming at 1680*1050 resolution.


so please tell me if I should go with an Athlon II x4 640 or a Phenom II x3 720 or is it mandatory to get a Phenom II x4 itself.


Depending upon the games you play, 2 or 3 fast cores might well work just dandy :lol: 

It also depends upon your budget, and I suspect (especially with that motherboard) you are anticipating a little performance tweaking, so here is the deal:

AMD Phenom II X3 715 Black Edition Heka - OEM: $71

CM Hyper N 520: $38 (before $10 rebate)

Luv that solid-copper base. Depending upon your RAMs you will be able to raise the system clock to 240-250MHz. With the unlocked cpu multiplier it's then up to you. 14x250MHz should not be an issue with 1333 RAM --- probably around 1.35v.

With 1600 RAMs 15x240MHz - probably around 1.375v.

My understanding is that the PhII x3 715BE is the 95w business-class B-73 providing max spec 1.425v to 73c. Looks spiffy - LOL


edit: I fergit ... it might unlock to a quad, too [:jaydeejohn:5]
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