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Does a CPU/GPU bottleneck occur? possible solutions

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  • Overclocking
  • Processors
  • CPUs
  • GPUs
  • Bottleneck
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June 24, 2013 9:30:14 AM

Hi. I currently have a Bulldozer FX4100 processor (3600MHz), with 8GB of 1866MHz RAM (custom profile in bios), and a GTS250 (256bits, 1GB DDR3) video card. I'm planning on buying a GTX770 Phantom(256bits, 2GB, 7000MHz) video card. Will it bottleneck my processor or not?

I'm mainly using the rig for gaming. There was another thread about a Radeon 7950 that is close in specs to the 770 Phantom, and someone said that an overclock of the CPU will do the trick. I did manage to take the CPU up to 4000MHz without any problems but right now that is a bit of an issue. So,

- how can i find out whether a bottleneck occurs or not?

- how much to overclock the CPU (or how to find out how much to do it?); currently it is very hot in my country and i had to disable the turbo boost of the processor as it led to operating temperatures of over 70 degrees Celsius, which made my computer shut down all of a sudden. I just cleaned the fan and the radiator and it seems to have solved the issue, but i can't be sure in the long run (i'm testing things in similar conditions right now).

- is there some kind of unwritten law about CPU/GPU bandwidth or operating frequencies that can give me some idea about the occurrence of bottlenecks? (basically the 770 Phantom has ~20 times more bandwidth than the CPU and twice the frequency).

- i've read that the FX4100 is a fake quad core and that in fact it has only 2 active cores. Is there a way to unlock the other two? (i suppose this ensures the GPU will not bottleneck it; also in my bios it appears there are 4 active cores and not 2 - is this fake?).

Thank you

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June 24, 2013 9:33:34 AM

Long story short, your GPU will not bottleneck the CPU. However, your CPU will bottleneck the GPU. Even if you overclock it very high, there will still be some bottleneck. The FX-4100 is not a very powerful CPU.
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June 24, 2013 9:35:24 AM

ksham said:
Long story short, your GPU will not bottleneck the CPU. However, your CPU will bottleneck the GPU. Even if you overclock it very high, there will still be some bottleneck. The FX-4100 is not a very powerful CPU.


If it's not too much to ask, could you explain (as thoroughly as you want) why this happens?
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June 24, 2013 9:37:47 AM

If you are considering a 770 (which is $$$), why not replace the CPU with a fx-8320?
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June 24, 2013 9:37:48 AM

If you are considering a 770 (which is $$$), why not replace the CPU with a fx-8320?
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June 24, 2013 9:40:10 AM

envy14tpe said:
If you are considering a 770 (which is $$$), why not replace the CPU with a fx-8320?


I don't have the money right now, and my current video card is almost 4 years old :)  in the long run i want to upgrade to an i5 or i7 but until then i'm wondering how the current(i.e. desired) cpu/gpu combination will perform.
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June 24, 2013 10:01:31 AM

Let's see...

A Gtx 770 is at least a 399.99 GPU.

If you want an overall system boost you could get fx-8320 and HD 7870 XT (Tahiti) for around 409.99.

You would have a 8 core CPU with plenty room for overclock and 1080p fully playable GPU.
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June 24, 2013 10:09:54 AM

psychatog said:
Let's see...

A Gtx 770 is at least a 399.99 GPU.

If you want an overall system boost you could get fx-8320 and HD 7870 XT (Tahiti) for around 409.99.

You would have a 8 core CPU with plenty room for overclock and 1080p fully playable GPU.


Like i said before, i have other plans for upgrades (basically i don't want any Radeon cards and i will get an intel quad core in some months because they should be better with nvidia cards), but until then i want to get the best video card for my budget since that is the oldest component i have. In my country the 770 Phantom is around 550$ (i live in Europe) and i would like to stick with it :)  As stated before, i'm trying to find out how bad the bottleneck is going to be and what can be done to alleviate it (including unlocking the 2 other cores of the CPU if they are indeed locked, even though my bios doesn't say that they are).
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June 24, 2013 10:10:56 AM

Crusader2010 said:
Hi. I currently have a Bulldozer FX4100 processor (3600MHz), with 8GB of 1866MHz RAM (custom profile in bios), and a GTS250 (256bits, 1GB DDR3) video card. I'm planning on buying a GTX770 Phantom(256bits, 2GB, 7000MHz) video card. Will it bottleneck my processor or not?

I'm mainly using the rig for gaming. There was another thread about a Radeon 7950 that is close in specs to the 770 Phantom, and someone said that an overclock of the CPU will do the trick. I did manage to take the CPU up to 4000MHz without any problems but right now that is a bit of an issue. So,

- how can i find out whether a bottleneck occurs or not?

- how much to overclock the CPU (or how to find out how much to do it?); currently it is very hot in my country and i had to disable the turbo boost of the processor as it led to operating temperatures of over 70 degrees Celsius, which made my computer shut down all of a sudden. I just cleaned the fan and the radiator and it seems to have solved the issue, but i can't be sure in the long run (i'm testing things in similar conditions right now).

- is there some kind of unwritten law about CPU/GPU bandwidth or operating frequencies that can give me some idea about the occurrence of bottlenecks? (basically the 770 Phantom has ~20 times more bandwidth than the CPU and twice the frequency).

- i've read that the FX4100 is a fake quad core and that in fact it has only 2 active cores. Is there a way to unlock the other two? (i suppose this ensures the GPU will not bottleneck it; also in my bios it appears there are 4 active cores and not 2 - is this fake?).

Thank you


OK this is gonna take some time...

1. Easiest way is to view whether your GPU is ever running at 100% when playing a game that is pretty demanding.

2. OC only with a decent aftermarket cooler, You can not OC a 4100 enough to avoid a bottleneck with a GTX770.

3. Ignore all frequencies and bandwidth, they are fundamentally different so it those numbers will not help you. Only way to realize where a bottleneck would be is by expanding your knowledge, reading reviews or testing equipment yourself, since the last point is expensive, stick to 1 and 2 points.

4. The FX4100 is a Quad core in most sense, it shares SOME resources that are used less often in CPU operation, but it still behave as a true quad core, more so than hyperthreading.

NOW, why does something bottleneck.

The CPU controls ALL communication within a system, this means that the tectures and any sort of "permission to execute" commands have to got to the CPU first before it can be sent to a GPU.
Now if a GPU can do MORE than a CPU can sent to it at any given time, that is what we call a bottleneck.
The CPU can not feed the GPU fast enough... So buying a GPU that is bottlenecked by the CPU is a waste of money unless you plan on upgrading the CPU in the near future...

SHo ok lets hope that was clear enough. Questions?
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June 24, 2013 10:18:21 AM

@Novuake: thank you for the explanations. I am indeed planning on upgrading the CPU too, hopefully this year. I'm thinking about a quad core i5 at around 3300MHz or something like that. An i7 is too pricy and i'm trying to avoid having internal an GPU since i will never use it.

One more question: how severe will the bottleneck be? (between my fx4100 and the gtx770). Can someone give me some quantifiable data? (e.g. the GPU will run at most at 80% because of the CPU)
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June 24, 2013 10:31:58 AM

if u manage to O.C afx4100 to 4.3-4.4ghz, then also it would bottleneck a gtx770.
Either upgrade up cpu or get a hd7870, it should work fine :) 
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June 24, 2013 10:47:32 AM

Crusader2010 said:
@Novuake: thank you for the explanations. I am indeed planning on upgrading the CPU too, hopefully this year. I'm thinking about a quad core i5 at around 3300MHz or something like that. An i7 is too pricy and i'm trying to avoid having internal an GPU since i will never use it.

One more question: how severe will the bottleneck be? (between my fx4100 and the gtx770). Can someone give me some quantifiable data? (e.g. the GPU will run at most at 80% because of the CPU)


Its not that clear unfortunately, but it will be a large percentage. My guess, GPU will max out at 70%.
What mobo do you have? You may be able to get a FX6300 into that board instead of getting a whole new mobo and i5 CPU.

What are your full system specs for that matter? Power supply exact model especially.
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June 24, 2013 11:06:02 AM

PSU: HPS-500-G12S, 500W (i know it's going to be close in power requirements but i think it will manage just fine from what i've read)
MBoard: Gigabyte 970A-DS3
RAM: 2x4 GB 1866MHz Kingston, 9-11-9-27 latencies
HDD: Seagate baracuda 1TB, 7200RPM
Asus DVDRW on SATA
Running Windows 7 Pro

Another question: is UNDERclocking the video card a solution for the time being? (until i change everything). I'm also hoping programs like Furmark or MSI Kombustor will give me an idea about the bottleneck after i get the 770gtx, but i'm not really sure they work that way. Can anyone recommend some software to test things out at max?

PS: at first i didnt want to get this AMD processor but i didnt have money for anything else (i upgraded from an intel E5300 if i remember correctly), and this one was the cheapest on AM3+ (i know i had the AM3 phenom4 choice, but i wanted to get the newest thing).
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June 24, 2013 11:24:50 AM

Well you are in luck. That board supports an FX6350 with a BIOS update. Which is what I would suggest you get in time.

Unfortunately you really need to consider getting a better PSU, its really not a true 500w and not good quality at all.

You also can not OC much on it either thanks to the 970 chipset. But that is fine if you get the FX6350.

Underclocking is pointless, you may as well get the GTX770 and just let it run till you get a better CPU.
HOWEVER my suggestion would be to wait for the GTX760 and GTX760 ti before you make your decision, the GTX770 would be an unnecessary waste of money considering your situation, for a single 1080p monitor its more power than you need.

DO NOT use Kombuster or Furmark, they are very bad benches and should only be used for burn ins.
Use Unique Heaven or 3D mark to bench.
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June 24, 2013 11:38:21 AM

Regarding the PSU, it is certified for 80% (which is more than enough for my current power requirements, and, as i've seen, for changing the video card to the 770 too), and i have read good reviews on it (and to my knowledge Sirtec is a reliable manufacturer). That's why i bought it actually :)  it was basically the best choice for price/efficiency/reliability. But this was a year ago :) 

The power requirements for the fx6350 are 30W higher than the fx4100, which means that i may need to also change the PSU to a more expensive one, which i don't really have the money for right now. That's why i was thinking about an i5, because it has 77W max power drain, and together with a newish motherboard it will lead to almost the same amount of money as the fx6350 + better PSU. The only added benefit to my choice is the intel-nvidia "link", rather than amd-nvidia (and going for a radeon is out of the question for me).

I'm hoping they will release the 760 at a reasonable price (and lower than the one of 770). Thanks for letting me know about it :) 
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June 24, 2013 11:48:39 AM

80 plus certification is only a measure of efficiency. NOT of the actual PSU, where did you get those reviews? Link me to them if possible.
A new CPU/mobo would cost considerably more than a 6350 and a PSU...
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June 24, 2013 11:58:48 AM

Novuake said:
80 plus certification is only a measure of efficiency. NOT of the actual PSU, where did you get those reviews? Link me to them if possible.
A new CPU/mobo would cost considerably more than a 6350 and a PSU...


I looked it up when i bought it a year ago (and i think some websites are in my native language, where some people tested the PSU to its limits and put forward some opinions). I don't have the links anymore unfortunately but i do remember researching several days about something for my budget and i ended up buying that one (i'll try to search again and see if anything comes up). There was also a Mushkin i think but that was too expensive.

I'm not sure, but i don't think i'm allowed to link the website from which i bought it (i.e. i would very much like some tips as to what PSUs are better in general).
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June 24, 2013 12:03:19 PM

Crusader2010 said:
Novuake said:
80 plus certification is only a measure of efficiency. NOT of the actual PSU, where did you get those reviews? Link me to them if possible.
A new CPU/mobo would cost considerably more than a 6350 and a PSU...


I looked it up when i bought it a year ago (and i think some websites are in my native language, where some people tested the PSU to its limits and put forward some opinions). I don't have the links anymore unfortunately but i do remember researching several days about something for my budget and i ended up buying that one (i'll try to search again and see if anything comes up). There was also a Mushkin i think but that was too expensive.

I'm not sure, but i don't think i'm allowed to link the website from which i bought it (i.e. i would very much like some tips as to what PSUs are better in general).


Well there are quiet a few. I generally stick to Seasonic manufactured ones. Here is an interesting article : http://www.tomshardware.com/reviews/power-supply-oem-ma...

You can also use this limited list, stick to Tier 1 to 3.
http://www.eggxpert.com/forums/thread/323050.aspx
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June 24, 2013 12:23:25 PM

Interesting read, thanks. Sirtec is not even on that list :)  but at least it's a legitimate OEM. Here's the site i buy from:

http://www.mediadot.ro/surse/filtre/sursa-modulara-nu/

It's in my native language, but you can use the filters at the top to search for manufacturers/power etc. I also found a website with a review on my PSU but it's all in my native language and there's no need to link it i believe. All of the manufacturers from tiers 1-3 i've looked at have quite high prices for a PSU of 650-750W and most don't even have the 80plus certification. Anyway, my PSU is made in China so maybe it's not truly Sirtec after all :)  but that's the quality of products we have here and there's very little i can do about it.

Also, adding up the prices again, a new intel CPU+mobo may cost around 30-40$ more than an fx6350+PSU - if i choose one of the more expensive motherboards, the total price being around 300$. Unfortunately these are the prices in my country.
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June 24, 2013 12:34:49 PM

Sirtec is on there as an OEM... They are not well known though.

Will that Intel setup have a decent mobo and CPU? Overclockable? Enough ports?
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June 24, 2013 12:53:41 PM

Novuake said:
Sirtec is on there as an OEM... They are not well known though.

Will that Intel setup have a decent mobo and CPU? Overclockable? Enough ports?


I haven't researched enough yet, but i'm thinking something in the lines of:

http://www.mediadot.ro/procesoare/procesor-intel-core-i...
(or the 3470 one, but it has integrated video and i'm trying to avoid it).
+
http://www.mediadot.ro/placi-de-baza/placa-de-baza-giga...

There may be better motherboards(more USB 3.0 ports, more SATA 3 ports) but i didn't have time to look thoroughly enough yet. The motherboard should allow the processor to be O.C.ed i believe.

Hopefully this processor will not be bottlenecked by the GPU :)  any idea how much i can overclock it(safely)?
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June 24, 2013 12:56:51 PM

You need a Z77 chipset and a K-series(3570K for example) to OC an Intel CPU. Z77 is considerably more than a H77 chipset.

Also why do you want to avoid onboard graphics?
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June 24, 2013 1:03:14 PM

Novuake said:
You need a Z77 chipset and a K-series(3570K for example) to OC an Intel CPU. Z77 is considerably more than a H77 chipset.

Also why do you want to avoid onboard graphics?


Someone said that the processor can be overclocked if the mobo allows it, but not too much (something like max +x4 more than the turbo frequency); for higher it does need the "K" suffix. Is that true?

It's not that i want to avoid them, but having a dedicated graphics card, i don't see the need for an on-board one (unless something happens to the former and i need to work on the computer). The problem is the processors tend to cost a lot more because of those integrated graphics, and also draw more power - both being things that i want to avoid if possible :)  i basically don't gain anything from having an integrated gpu right now.

The price for a Z77 is similar it seems: http://www.mediadot.ro/placi-de-baza/placa-de-baza-msi-...
Not sure about the quality though.
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June 24, 2013 1:12:25 PM

Crusader2010 said:
Novuake said:
You need a Z77 chipset and a K-series(3570K for example) to OC an Intel CPU. Z77 is considerably more than a H77 chipset.

Also why do you want to avoid onboard graphics?


Someone said that the processor can be overclocked if the mobo allows it, but not too much (something like max +x4 more than the turbo frequency); for higher it does need the "K" suffix. Is that true?

It's not that i want to avoid them, but having a dedicated graphics card, i don't see the need for an on-board one (unless something happens to the former and i need to work on the computer). The problem is the processors tend to cost a lot more because of those integrated graphics, and also draw more power - both being things that i want to avoid if possible :)  i basically don't gain anything from having an integrated gpu right now.

The price for a Z77 is similar it seems: http://www.mediadot.ro/placi-de-baza/placa-de-baza-msi-...
Not sure about the quality though.


First part, true. But that kind of OCing does not gain you anything.

The integrated graphics cost very little extra.
The only CPUs from intel without onboard graphics are are P-versions. They are chips that are defective in small ways which has had their onboard GPUs disable by Intel. They do not use less power if you have a discreet GPU installed, as soon as the GPU is installed the onboard graphics disables anyway. On top of that onboard can be useful as you said.

That board, HORRIBLE... LOL
Cheapest suggested Z77 to OC on is the Asrock extreme 4 Z77 mobo and a 3570K.
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June 24, 2013 1:15:50 PM

Why is that mobo so bad? :)  the asrock z77 extreme4 is around 60$ more expensive. I need to look up what is so special about it with respect to the other non-extreme ones :D 
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June 24, 2013 1:26:58 PM

Crusader2010 said:
Why is that mobo so bad? :)  the asrock z77 extreme4 is around 60$ more expensive. I need to look up what is so special about it with respect to the other non-extreme ones :D 


Hahaha the Extreme is just a branding. When OCing stuff like VRM quality determine lifespan of the mobo. The Extreme 4 is meant for OCing, the G41 is not. Hell the cheapest MSI OC board I can suggest is a G65, even the G45 is crappy.
Quality = reliability and stable OCing.
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June 24, 2013 1:32:58 PM

Novuake said:
Crusader2010 said:
Why is that mobo so bad? :)  the asrock z77 extreme4 is around 60$ more expensive. I need to look up what is so special about it with respect to the other non-extreme ones :D 


Hahaha the Extreme is just a branding. When OCing stuff like VRM quality determine lifespan of the mobo. The Extreme 4 is meant for OCing, the G41 is not. Hell the cheapest MSI OC board I can suggest is a G65, even the G45 is crappy.
Quality = reliability and stable OCing.


Question is, do i really need to OC an i5 well above let's say 3700-3800MHz? i hope it won't get bottlenecked by the gpu :)  won't cheaper mobos handle that too?

As i understand it (http://www.tomshardware.co.uk/forum/316547-30-differenc...) there's really no need for more expensive ones unless you want to test stuff or go near the limits (and i'm in no need for extra slots/ports in general). Please correct me if i'm wrong :D 

PS: Thanks everyone for your answers and your help in making me reach a decision!
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June 24, 2013 2:00:24 PM

Crusader2010 said:
Hi. I currently have a Bulldozer FX4100 processor (3600MHz), with 8GB of 1866MHz RAM (custom profile in bios), and a GTS250 (256bits, 1GB DDR3) video card. I'm planning on buying a GTX770 Phantom(256bits, 2GB, 7000MHz) video card. Will it bottleneck my processor or not?

I'm mainly using the rig for gaming. There was another thread about a Radeon 7950 that is close in specs to the 770 Phantom, and someone said that an overclock of the CPU will do the trick. I did manage to take the CPU up to 4000MHz without any problems but right now that is a bit of an issue. So,

- how can i find out whether a bottleneck occurs or not?

- how much to overclock the CPU (or how to find out how much to do it?); currently it is very hot in my country and i had to disable the turbo boost of the processor as it led to operating temperatures of over 70 degrees Celsius, which made my computer shut down all of a sudden. I just cleaned the fan and the radiator and it seems to have solved the issue, but i can't be sure in the long run (i'm testing things in similar conditions right now).

- is there some kind of unwritten law about CPU/GPU bandwidth or operating frequencies that can give me some idea about the occurrence of bottlenecks? (basically the 770 Phantom has ~20 times more bandwidth than the CPU and twice the frequency).

- i've read that the FX4100 is a fake quad core and that in fact it has only 2 active cores. Is there a way to unlock the other two? (i suppose this ensures the GPU will not bottleneck it; also in my bios it appears there are 4 active cores and not 2 - is this fake?).

Thank you


Well i know AMD is not the best option for gaming, and your 4100 is not a very powerful CPU, but im sure if you play @1080p or higher you won't lose a lot of performance while gaming.

Your CPU performance is located between AMD A6 3650 and AMD A8 3850: http://www.tomshardware.com/reviews/gaming-cpu-review-o...

And those CPUS had a great performance handling a single GPU in this article: http://anandtech.com/show/6985/choosing-a-gaming-cpu-at...

So if you are going to play your GTX 770 at least 1080p, you will enjoy higher frame rates.



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June 24, 2013 2:25:44 PM

@psychatog: yes, i intend to play everything at a 1900x1080 resolution or 1900x1200. Thank you very much for your links!

One last question: what's the best software to test cpus/gpus/bottlenecks etc? i want something that pushes everything to the limit (like furmark and msi kombustor). Anyone knows others(better)?
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June 25, 2013 12:18:13 AM

to check ur cpu's stabililty after O.C ing run PRIME95 and test it for 5-6hrs and see whether ur cpu is stable or not.
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