AMD Radeon HD 7850 and 7870 review (Page 23)

AMD Radeon HD 7850 and 7870 review

Graphics cards 1054 Page 23 of 24 Published 2012-03-04 14:00 by Hilbert Hagedoorn

Reviews

Overclocking the Radeon HD 7850 and 7870

Overclocking The Radeon HD 7850 & 7870

As most of you know, with most videocards you can apply a simple series of tricks to boost the overall performance a little. You can do this at two levels, namely tweaking by enabling registry or BIOS hacks, or very simply to tamper with Image Quality. And then there is overclocking, which will give you the best possible results by far.

What do we need?One of the best tools for overclocking NVIDIA and ATI videocards is our own AfterBurner which will work with 90% of the graphics cards out there. We can really recommend it, download here.

Where should we go?
Overclocking: By increasing the frequency of the videocard's memory and GPU, we can make the videocard increase its calculation clock cycles per second. It sounds hard, but it really can be done in less than a few minutes. I always tend to recommend to novice users and beginners, to not increase the frequency any higher than 5% on the core and memory clock. Example: If your card runs at 600 MHz then I suggest that you don't increase the frequency any higher than 30 to 50 MHz.

More advanced users push the frequency often way higher. Usually when your 3D graphics start to show artifacts such as white dots ("snow"), you should back down 10-15 MHz and leave it at that. Usually when you are overclocking too hard, it'll start to show artifacts, empty polygons or it will even freeze. Carefully find that limit and then back down at least 20 MHz from the moment you notice an artifact. Look carefully and observe well. I really wouldn't know why you need to overclock today's tested card anyway, but we'll still show it.

All in all... do it at your own risk.

The Radeon HD 7850

Original	This sample	Overclocked
Core Clock: 860 MHz	Core Clock: 860 MHz	Core Clock: 1050 MHz
Shader Clock: 860 MHz	Shader Clock: 860 MHz	Shader Clock: 1050 MHz
Memory Clock: 4800 MHz	Memory Clock: 4800 MHz	Memory Clock: 5800 MHz

Open up AMD Overdrive or AfterBurner. Now we need to free the card up from TDP restrictions first, so all the way down move the Power Control settings slider towards 20%. So hypothetically if the max allowed board TDP is 100 Watts x 1.20 = 120W of overclocking headroom.

Overclocking wise the card will allow itself to be clocked to 1050 MHz. Memory can be boosted as well, just max it out at 5800 MHz.

So for the 7850 you max out the sliders as that is the maximum allowed overclock by AMD overdrive. The performance however will increase directly to the level of a R7870. But sure, the R7850 definitely is more restricted when it comes to overclocking.

Radeon HD 7800

The Radeon HD 7870

Original	This sample	Overclocked
Core Clock: 1000 MHz	Core Clock: 1000 MHz	Core Clock: 1175 MHz
Shader Clock: 1000 MHz	Shader Clock: 1000 MHz	Shader Clock: 1175 MHz
Memory Clock: 4800 MHz	Memory Clock: 4800 MHz	Memory Clock: 5800 MHz

For the R7870 we once again open up AMD Overdrive or AfterBurner and free the card up from TDP restrictions first, so all the way down move the Power Control settings slider towards 20%.

Overclocking wise the card will allow itself to be clocked to roughly 1100 MHz on the core easily and that's without voltage tweaking. We where actually able to push he card towards a nice 1175 MHz on the GPU core, but that said it was barely stable enough, you'll likely end up at 1100~1125 MHz. Memory can be boosted as well, just max it out at 5800 MHz.

Below some numbers based on the overclock we where able to pull off. Both cards are very flexible in terms of overclocking alright. Granted he entire Radeon HD 7000 series is a gem when it comes to tweaking.

Radeon HD 7800