Why video card disrupts the processor performance (CPU)?

[Helton Bayer]

Hello good afternoon.
I am Brazilian and I'm using google translator, so sorry for some mistranslated term.
My computer is old and slow compared new technologies, but still able to convert and burn Blurays 1080p.
A Q9450 Core2Quad, Asus Rampage Formula motherboard socket 775, 4gb DDR2 800, FN-R 750W F-NEW supply, video card MSI GeForce 210 - 1GB DD3 - 64 bits.
Round 1:
With this setting, converting 4 episodes of Dragon Ball Super 001-004 - 1080p - HDTV - x265 + Legend, set to 4 conversions with cpu and 2 for hardware optimization, the score was 2 episodes to 4 fps each with GPU and 2 episodes to 7 fps with CPU.
Trying to improve performance, I bought a video card GeForce 9800 GT - 1 GB DDR3 - 256 bits. And really happened, episodes converted by GPU accelerated from 4 to 5x faster than the old video card. HOWEVER, the processor almost stopped working.
And the new score was 2 episodes 17-20 fps each with GPU and 2 episodes 1 fps each, reaching ZERO each after 10 minutes conversion. While GPU was up from 17 to 20 fps each episode.
That is, in my humble opinion, this new 9800 GT video card is disturbing, for some reason unknown to me, the processor performance C2Q 9450.
If the score stayed 17 fps for GPU and 7 for CPU, I was really happy, this was the intention to buy a new video card.
Round 2:
How not to give up easily, I changed again the video cards, I could have given some problem in the processor, motherboard or power supply.
But no, the score remained the same.
I changed again and put back the 9800 GT, the same score.
Round 3:
More dissatisfied than ever, I decided to do another test, this time on another platform. I asked a friend from installing the 9800 GT and the 210 on your PC AMD Phenom X4 2.5 GHz - 4 GB DDR2, power supply Seventeam 500W.
And the result was remarkably equal, saved the performance ratios from one platform to another, which in this case is not very big, while my C2Q is at 7 fps, the phenom x4 it is at 5 fps with 210. It seems, but results in 1 hour difference in the final of 10 episodes.
And with the 9800 GT his cpu is at zero from the beginning.
That is, the 9800 GT hurt the performance of the AMD Phenom X4 much as hurt the performance of my Intel C2Q 9450.
Round 4:
Now I'm using this forum, because I really do not know what to do.
Unfortunately, here in Brazil, the most expensive parts cost 4x than in the USA, because here one US dollar costs 4 reais. So, the changes need to be studied.
I thought of changing the 9800GT with 112 cores by GTX 750 TI with 640 cores, to improve the speed of further conversions, since my processor is very limited to 1080p.
But now comes the reason I'm writing here: there is a risk of happening the same problem, and the processor being limited by the increased GPU processing capability with 640 cores? Or he can go back to work at 7 fps when working alongside the 16 cores of the Geforce 210?
Logically, I imagine that the problem may worsen.
But it can also be an outdated technology problem, and you guys are always updating the software (magnificent, in my opinion, only lack in advanced customization of menus because the basic is a show).
Anyway, I reported the problem and what I did to try to solve, now would like a software support, if possible, as the next step in my choice.
I accept different suggestions, provided they are not too expensive.
Thank you in advance.
Helton

[Helton Bayer]

Hello good day.
I do not correctly explained the problem or the situation is new for everyone who saw and said nothing?
No idea?

[JJ]

One possibility; your system is too slow to handle the amount of data that video card can process.
Memory and harddrives simply can't handle that much and CPU tries to use harddrive as swap memory slowing everything to crawl.

[Helton Bayer]

thanks JJ
I think that your idea is the best hypothesis.
Thank you so
Helton