6GB 800Mhz RAM
ATI HD3870 512MB
I want to upgrade my GPU, but i am not sure which one to choose for this older CPU. I am running it just on stock frequency (2,4), because it´s kinda damaged or just "lazy" one - i can overclock to 2,9 max with high voltage raise, so it´s too hot to overclock further. I am considering HD 6850, but i am worried it will be throttled by slow cpu, and cheaper GPU (6770 for example) will run approx. the same. Which GPU would you recommend for my configuration?
Btw. i want it just for gaming, at 1280x1024 or 1280x720 with slight use of AA + AF.
Thanks for advices
At your resolution your framerates are going to be more CPU bound than GPU bound in most cases. If you can overclock your CPU to 2.9 GHz that will certainly help. If you don't intend to upgrade to a higher resolution display, a 6770 will do fine and should be able to deliver high setting without much trouble, though some CPU intensive games, particularly the ones that really favour quad cores may run poorly. The 6850 is a good deal faster than the 6770 but it is overkill for 1280x1024 and 720p, and probably will be bottlenecked unless you overclock up to 2.9 GHz, and even then there may be bottlenecking issues for the more CPU heavy titles.
i have the same cpu as you, it can get to 2.7ghz without voltage and my 3.24 ghz is achievable with a small voltage increase. I can tell you the cpu will be holding you back along with the gpu. I have upgraded to a 6850 and in some games its still a bit slow. You really need a quad core for many new games to run smoothly. At that resolution there is no point going to a 6850, just get a 5770/6770.
Thanks for advices!
My CPU asks for lot of voltage, when i overclock to 3,2ghz i have to set cca 1,4V voltage, otherwise the system is unstable and i experience artifacting in videos and games. Temperatures are really high too, after running som burn tests CPU soon reaches t-case max 85°C and is throttled. It´s too warm anyway, with stock cooler i had 65°C at idle on stock frequency, i changed it for Scythe Ninja and i have cca 52 (idle, stock frequency).
I don´t plan display upgrade for year or two, so i just stick with 6770.
Or is there some better option? From nVidia for example?
The nvidia equivalent would be the GTX 550Ti it has similar performance to the 6770. The 550ti does tend to be a little pricier than the 5770/6770 though, so unless you really want PhysX, you play a game that very heavily favours nvidia cards, or you have an application that would run faster with CUDA, it probably wouldn't be worth getting, unless you can find a good deal on one.
What you are referring to is memory bandwidth. A higher number is generally better but it is only one of many factors in determining how fast a graphics card is. The 6770 has a a lot more shaders, and considerably faster memory than your old 3870, leading to considerably greater performance, despite the lower memory bandwidth. The 550Ti's slightly faster memory bandwidth does not really translate to significantly higher performance vs. the 6770. For cards in the performance bracket you are looking at, you are unlikely to saturate a 128 bit memory bandwidth anyhow, they simply aren't fast enough for that.
judging by the heat of the cpu you need some exhaust fans in your case, or the room needs aircon to bring down the ambient temps. Heat would be the reason for the instability. If the cpu is getting that hot with aftermarket cooler, any GPU you put in there will probably overheat also.
There are two 12cm fans in my case, intake(front) and outtake(rear), another 12cm fan is on Ninja cooler blowing "through" it. Whole Ninja cooler is really hot in burn mode, so i believe it´s CPU own fault, not bad cooling system. (But i blame 775 plastic cooler clips a bit, if there were screws i would just tighten it really hard and temperatures would be better, maybe).
BUT I changed thermal grease compound recently, cleaned both CPU and cooler before, and temepratures are much better now, i can run cpu at 3,0 ghz without problems, in heavy load burn test (which before failed because of passing 85°C) it runs "cool" - just around 72°max