How good are the customised Radeon HD 7970s and 7950s? To give an answer to this question, we have looked in detail at the Asus, HIS, MSI, PowerColor, Sapphire and XFX releases as well as the reference cards. When heat, noise and overclocking are all taken into account, which one is the best Radeon HD 7900?
Numerous variants, out rapidly
Quite unusually for high end graphics cards, the customised models from AMD’s partners came onto the market very quickly, some even arriving at launch of the cards, notably the XFX Radeon 7970 Double Dissipation Edition, though of course this card is based on the reference PCB. Asus was the first to customise the Radeon HD 7970 entirely with the DirectCU II model, with the competition hot on its heels.
AMD actually produced two reference models of the Radeon HD 7950. The first, derived from the Radeon HD 7970, seems to have been reserved for the press and the second made available to the different graphics card manufacturers as a base model from which to come up with their own designs.
A graphics card can be customised either with a new cooling system or a new PCB or both at the same time. On most of the Radeon 7950s available at launch, the manufacturers have used the reference PCB (different to the press release) made in the factory of their choice with components of their choice (but which of course follow certain criteria) and have settled for modifying only the cooling system.
Customising the cooling system allows them to differentiate their cards or try to reduce somewhat their costs in comparison to the reference cooler which may be relatively costly. To keep production costs down on their high end in-house variants, the biggest manufacturers have elaborated more or less generic cooling systems that they can roll out on the maximum number of models, allowing them to benefit from an economy of scale in terms of production and R&D costs.
It's not all about the cooling system however, notably with the Radeon HD 7900s which have a very high margin for overclocking calling for a sufficiently sturdy power stage to make the overclocking potential fully exploitable. We will be checking to see if the power stages used are solid enough, particularly on the Radeon HD 7950s on which a second reference PCB optimised for cost reduction has been used by numerous manufacturers.
In this test we will concentrate on comparing the different Radeon HD 7900s between themselves. For more details on performance in comparison to the competition, we invite you to consult the reports dedicated to such comparisons: Radeon HD 7970
and Radeon HD 7950
Here’s the list of the cards tested. This will be added to as new models reach us:
AMD Radeon HD 7950 press edition
Reference AMD Radeon HD 7970
Asus Radeon HD 7970 DirectCU II TOP
HIS Radeon HD 7950
MSI Radeon HD 7950 Twin Frozr III
MSI Radeon HD 7970 Lightning
PowerColor Radeon HD 7950 PCS+
Sapphire Radeon HD 7950
Sapphire Radeon HD 7950 OverClock
XFX Radeon HD 7950 Black Edition Double Dissipation
XFX Radeon HD 7970 Double Dissipation
Defective test samples
Before getting further into the report, we can’t but mention the many problems we’ve had that have contributed to delaying it: defective fan fixtures, screws that have fallen off into our hands on removing cards from their packaging, insufficient coolers pressure against the GPU, changing of bios’ and so on. Some of the press samples seem to have been assembled slap dash before the employees of the different factories headed for the hills for the Chinese New Year. We certainly hope that more attention is given to the cards on sale in stores!
Although we were able to resolve most of these issues, sometimes with a second sample card that had been corrected, we still haven’t been able to test the Asus Radeon HD 7950 DirectCU II. The fixture system, such as the one on the first sample model, doesn’t exert enough pressure on the GPU and one of the four screws doesn’t have any purchase on anything. You can imagine what might happen when the card is placed horizontally in a casing... If you don't, here is what we noticed with the press sample as well as a commercial sample : GPU overheating
On one hand Asus has recognised the issue, which can be rectified simply by adding a washer to the screw (moreover, this is what all the other manufacturers have done, AMD's spec probably not proving sufficiently precise originally), but on the other Asus Taiwan is dragging its feet in terms of confirming that the first available cards in stores won’t suffer from this problem. As things stand, we therefore advise you to avoid this model. Our current interpretation is that the manufacturer has slightly modified its production procedure for this card, or is currently doing so, to make sure the cooler fixture functions properly but does not intend to admit to the fault on the first shipments, safe in the knowledge that the issue won’t cause an immediate crash on every sample.