ATI Radeon HD 5970: The Undisputed Performance Champ

norman

AMD’s Radeon HD 5970 takes the performance crown, and now offers DirectX 11 GPUs top to bottom.

You can forgive AMD for stealing a line from Nvidia’s playbook. From the name and marketing materials, it’s not obvious that this card is a dual GPU card. One AMD chart even refers to the card as the “ATI Radeon HD 5970 GPU,” much like Nvidia’s 295 GTX is a dual GPU card that’s sold as if it were a normal graphics card.

Let’s take a quick look at the speeds and feeds of the new card, and then discuss additional features. We’ll compare them to the Radeon HD 5870 single GPU card; there are differences in core and memory clock speeds.

ATI Radeon GPUs Compared
Model
HD 4870
HD 5970
GPU
Single HD 5870 GPU
Dual HD 5870 GPUs
Stream Processors
1600
3200
Core Clock
850MHz
725MHz
Memory
1GB 1200MHz GDDR5 2GB 1000MHz GDDR5
Texture Units
80
160
ROPs
32
64
Memory Data Rate
4.8Gbps
4.0Gbps
Compute Performance
2.72TFLOPs 4.64TFLOPs
Idle Power 27W
42W
Max Power
188W
294W


Most features simply double, since there are two identical GPUs with the same memory per GPU. However, note the memory bandwidth is lower, since the memory clock is lower. Also, overall compute performance isn’t quite double, since the engine clock for each GPU defaults to 725MHz, rather than the single GPU 5870’s 850MHz.

In addition to the paired GPUs, the card maximizes performance with a new second generation PLX PCI Express 2.1 bridge chip. This speeds up communications between the two GPUs.

The older Radeon HD 4870 X2, AMD’s last dual GPU card, often suffered from serious overheating problems, so AIT has taken steps to improve overall thermal efficiency. The first step is to used specially screened GPU chips with the minimum amount of leakage current. The thermal system consists of a vapor chamber, with heat dissipation via a fully vented exhaust system. Finally, a multipoint, programmable PWM fan controller ensures fan speeds consistent with overall thermal output. The whole affair is rated to dissipate 400W, or over 100W of headroom.

The use of low leakage GPUs suggests that the core clock speeds could be pushed higher than the default 725MHz. Given that the card can dissipate 400W of overall thermal output, ATI has decided to leave the card unlocked, letting users overclock it to their heart’s content. The company is even making available an overvoltage tool, and suggests that the card has enough headroom to push the engine clock to above the 850MHz of the single GPU HD 5870 and the memory speeds up to the 1200MHz of the 5870. In The HD 5970 also sports sophisticated digital voltage regulators, real time power monitoring and Japanese pure ceramic capacitors, which facilitate higher clock speeds. (The reason for the more conservative default clock speeds is that the company needs to make allowances for the thermal environment inside PC cases, which may be less optimal.)

What about power efficiency? The HD 5970 offers the same clock gating capability as the single GPU variant. In addition, the card offers an ultra low power state that puts one GPU to sleep, which cuts the overall power draw of that GPU by half the normal idle performance. The card idles at 42W, only 15W higher than the 27W of the HD 5870. Of course, the card sucks 294W at full throttle – and that’s at the default clock speeds. So you’ll need a power supply with the later PCI Express 8-pin power connector – the HD 5970 uses one eight pin and one six pin connector from the PSU.

The onboard connectors are slightly different from the original HD 5870: two DVI-I connectors and one mini-DisplayPort attachment, first popularized with Apple’s MacBook Pro laptops and iMacs. All three can be attached simultaneously, and drive three displays at the same time. Note that most DisplayPort enabled monitors which aren’t Apple displays ship with standard sized DisplayPort cables, so you’ll need to obtain a mini-DisplayPort to standard DisplayPort cable if you want to take advantage of that connection option.

Performance

We tested three graphics cards: the Radeon HD 5970, the Radeon HD 4870 X2 and the GeForce 295 GTX . Note that the 295 GTX only ships with 1792MB of GDDR3 memory (896MB per GPU). The Nvidia GPUs on the 295 GTX have a full complement of 240 shaders, like the 285GTX, but only a 448 bit wide memory bus, similar to the GeForce GTX 260 line of graphics chips.

All games were run at two settings: 1920x1200, 4xAA and 2560x1600 4xAA. All detail settings on all games were maxed out. We also report the results from 3DMark Vantage’sdefault, performance setting and the extreme setting. In addition, we’re tossing in the results from the eVGA GeForce 285 GTX SSC and XFX Radeon HD 5870 at the 1920x1200 resolutions, so you can get an idea as to how much you gain from the dual GPU cards.

We used our standard graphics test system for benchmarking graphics cards:

Test System
Component
Model
CPU
Intel Core i7 975 @ 3.33GHz
Motherboard
Asus Rampage II ExtremeX58
Memory
6GB Corsair Dominator DDR3-1600 @ 1333MHz
Hard Drive
Seagate 7200.12 1TB
PSU
Corsair 850W
Operating System
Windows 7


The HD 5890 seems much better behaved than its predecessor, the HD 4870 X2. Although the HD 5970 fan noise became quite audible at high loads, it seemed much quieter than the 4870 X2. More telling was our experience removing the cards immediately after completed benchmarking runs. The 4870 X2 was extremely hot to the touch – we had to handle it carefully to avoid burnt fingers – while the 5970 was cooler to handle (though still very warm.) Much of this was no doubt due to the vapor chamber covering the back side of the card.

As we expected from our previous experience with the Radeon HD 5870, the dual GPU HD 5970 pretty much smokes the competition. At its targeted $599 price point, the performance needs to be stellar – and it is. Let’s check out the performance charts.

1920X1200 4XAA
Model
eVGA 285 GTX SSC
Radeon HD 4870 x2
GeForce GTX 295
XFX 5870 Radeon HD 5970
3DMark Vantage (Perf)
13941
14458
19342
17089
21089
3DMark Vantage (Extreme) 6276
6574
9241
8312
12084
HAWX 62
78
93
68 104
Far Cry 2 (Action)
47
67
62
62
75
Far Cry 2 (Ranch Long)
56
77
73
74
116
BattleForge (DX10)
46
36
33
47
61
Crysis (DX10)
22
33
29
32
44
Resident Evil 5
87
126
115
100
135
X3: Terran Conflict
93
101
100
101
107
STALKER: Clear Skies
27
38
40
36
53

2560x1600 4XAA
Model
Radeon HD 4870 X2
GeForce GTX 295
Radeon HD 5970
HAWX
53
54
76
Far Cry 2 (Action) 18
59
65
Far Cry 2 (Ranch Long) 50
55
82
BattleForge (DX10) 23
20
39
Crysis (DX10) 19
18
24
Resident Evil 5 88
85
102
X3: Terran Conflict 90
59
101
STALKER: Clear Skies 22
20
31

There’s no question the Radeon HD 5970 is the fastest single desktop graphics card you can buy today. The real question is if it’s worth $200 more than a single Radeon HD 5870. Certainly if you’re running a 1920x1200 display, we’d recommend the single GPU card. But if you’re running triple displays, or a 30-inch, 2560x1600 monitor, and you want to push polygons at full resolution, you should consider the Radeon HD 5970. But make sure you’re willing to pay the cost.

Another note: this card is enormous. It’s an actual foot-long graphics card; make sure you’ve got a case deep enough to handle it.

Then there’s the whole issue of CrossFire. The HD 5970 is essentially a pair of downclocked HD 5870s in CrossFire mode. When the game can take advantage of CrossFire – as it does in our benchmarks – you can see huge performance gains. If the game can’t make use of CrossFire, then you own a pricey single GPU card that doesn’t run as fast as the HD 5870.

But what about running TWO of these cards in CrossFire mode? Find out on the next page.

Dual-5970 CrossFire Performance

We were fortunate enough to get not one, but two 5970 cards to test in our lab. The two cards came in Falcon Northwest's brand new Talon PC, which is the first 5970-equipped system we've reviewed.

You can read our full review of the kick-ass Falcon Northwest Talon here , but the system specs are below for your reference. Note that the Talon is a Lynnfield-based Core-i7 system, overclocked to 3.93GHz, as opposed to the 3.33GHz Core i7-975 Bloomfield proc we used in our testbed to benchmark the lone 5970 card.

Specifications
Processor Intel 2.93GHz Core i7-870 @3.83GHz
MOBO
MSI P55-GD65
RAM 8GB Crucial DDR3/1600
Videocard
Two MSI Radeon HD 5970 in CrossFire mode
Soundcard
Onboard
Storage
Two Intel X25-M 80GB in RAID 0; 1TB Samsung Spinpoint 7,20rpm hard drive
Optical
Lite-On 22x DVD burner
Case/PSU
Silverstone case with Exotix paint job and 1,000 Silverstone PSU

In addition to a 48-hour plus burn-in period, we wanted to push Falcon Northwest’s dual-Radeon HD 5970 cards on something a bit harder so we connected the FNW Talon to a 30-inch 2560x1600 panel and cranked several benchmarks to maximum. The result? Impressive. Although, the drivers we used were still fairly early, the performance of the card is unquestionable. We had some concerns of running the card in a dual x8 mode (a limitation of the P55 chipset and Lynnfield platform) instead of full x16’s that an X58 platform would give us but the results don’t seem to show too much to be concerned about. The cards seem to offer better than expected scaling, even with early drivers.

Dual-5970s on Falcon Northwest's Talon PC

HD 5970 Crossfire On
HD 5970 Crossfire Off
3DMark Extreme Overall (1900x1200)
18954
11686
3DMark Extreme GPU (1900x1200) 18763
11384
3DMark Extreme CPU (1900x1200) 23498
23561
3DMark Extreme GPU (2560x1600)
13494
9076
3DMark Extreme CPU (2560x1600) 23387
23399
Crysis, Very High, (2560x1600) 34.4 FPS
27.1 FPS
Far Cry 2 Ultra High (2560x1600)
185.2 FPS
107.4 FPS
Crysis, 1900x1200 (NO AA) 66.3 FPS
(did not run)
Crysis, 1900x1200 (16X AA)
64.3 FPS (did not run)

Note that in Crysis, enabling 16X Anti-Aliasing doesn't seem to affect the framerate with CrossFire enabled.

Finally, a note on overclocking. The AMD overvolting tool has two settings for core and memory. You can overvolt the GPUs, overvolt the memory or both. Using the tool, we pumped up both voltage settings, then found the card to be stable at 870MHz core and 1250MHz memory (17 and 25% respectively.) Curiously, though, we saw little actual performance gain. 3DMark Vantage (extreme setting) only saw a 1% increase, from 12084 to 12182. We got two additional FPS in Crysis and either no increase or slight decreases in frame rate for Far Cry 2 and STALKER: Clear Skies. We probably need to do a better job of balancing memory and core clocks, but our initial experiences suggest that overclocking may not be worth the effort.

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