Size, noise and heat generation
The generic models sent to the press look exactly like the Radeon HD 7970 and Radeon HD 7950. The Radeon HD 7870 is nevertheless 2.5 cm shorter than the 7970, making it 'just’ 25 cm long.
A radial fan (or blower) is still used in the cooler. This has the advantage of sending the hot air straight out of the casing, unlike models with an axial fan such as the Radeon HD 7770 for example.
The fan nevertheless proved slightly disappointing as it makes quite a whirring noise, even at idle, though we should say that in a standard casing it shouldn’t be louder than your other components. In a casing designed to be quiet however, it could be a little more annoying. Once you’ve fired up a video game, the whirring is kept at an acceptable level and shouldn’t be too disturbing.
We may be repeating ourselves but we do want to underline the excellent energy consumption of the AMD Radeon 7000 series. The 7870 is no exception to the rule and gives a very good showing: 89 Watts at idle and 312 Watts in games. These readings represent the energy consumption of the entire test machine and are identical to those taken under the same conditions for the Radeon HD 6870. As we'll see below, performance is significantly up, which only goes to show how well AMD has done here.
Better still, the excellent ZeroCore Power feature is of course included and gives a 16% reduction in energy consumption at idle and allows you to turn the fan off. For this, the computer has to be configured so that it switches the screen off after a given period of time. As soon as the screen goes into standby, the card is almost entirely switched off and only consumes 3 Watts, bringing the overall energy consumption of our test machine down to 74 Watts. This feature will delight those who leave their computer turned on all the time.
Technically speaking, the Radeon HD 7870 falls between the Radeon HD 7770 and the Radeon HD 7950, but remains closer to the HD 7950. The GPU clock is thus identical to that on the 7770, namely 1 GHz, while the processing units - which can, to simplify, be compared to the cores on a CPU - number 1280, which is double the number on the 7770. The Radeon HD 7950 has 1792.
To finish with the tech spec, the 2 GBs of memory are at 1200 MHz, compared to 1250 MHz on the 7950. The memory comes with a 256-bit memory bus, which is almost exactly midway between the bus on the 7770 (128-bit) and the 7950 (384-bit).
So then, what do all these processing units, memory and clocks give in terms of performance? Well, the HD 7870 is a faster card than the Nvidia GeForce GTX 570 (+4%) and most impressively 37% up on its predecessor, the Radeon HD 6870. The Radeon HD 7950 is still 11% faster.
Once again, AMD has given us a very good card: current games can be played with all the graphics options on and on Full-HD screens. The real achievement is that the notable performance gain has been achieved without any increase in energy consumption!
Consult the performance index table