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AMD Radeon HD 6450 and HD 6670 graphics card review

by Tarinder Sandhu on 19 April 2011, 05:00 3.0


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Almost-complete 6-series line-up

Mainstream love

The big guns of the graphics-card world have already fired for this year. Heck, even the mid-range stack for AMD and NVIDIA is pretty well set, with Radeon 6000 series going up against the GeForce GTX 500 cards. But now it's time for the little fellas to strut their stuff, as the two GPU companies release a wave of low-end discrete cards.

Discrete graphics cards - and these are add-in boards that usually slot into a motherboard's PCIe x16 slot - start at around £30 for a bottom-feeding model and rise up to £600 for a card with more computational ability than a fully-functioning Deathstar.

Cheap(er) graphics cards are like ants, because it's by sheer volume that they make themselves felt. AMD and NVIDIA know that the sub-£80 market is absolutely critical to the bottom line, and enticing users away from a PC's integrated graphics and locking them into your brand is one sure-fire way to keep the bean counters at bay.

AMD's current sub-£100 stack is composed of last year's Radeon HD 5000 family of GPUs, going from the £30 HD 5450 to the £95 HD 5770. The higher the number, the better the performance, generally speaking.

Now, though, the chip company is bringing Radeon 6000-series love to this market by releasing the HD 6450, HD 6570 and HD 6670 GPUs. Here's how they line up against the established Radeon brand.

Price R5K R6K
<£40 5450 6450 D3 and G5
£50-£60 5550/5570 6570 D3 and G5
£60-80 5670 6670 G5
£80-£99 5750/5770 ?

The table makes sense insofar as AMD has introduced a 'new' generation of GPUs at roughly the same price as the incumbents. The one identifiable gap remains the £80-£99 market, where the HD 5750/70 aren't due to be replaced this quarter. This means that AMD will have a couple of 5-series cards wedged between an otherwise top-to-bottom 6-series line-up.

Minor improvements

But here's where it becomes difficult for AMD. You see, the Radeon HD 5K GPUs are (almost) the pinnacle of the engineering efforts that began with the Radeon HD 2900 XT. These graphics cards are based on a mature 40nm process from TSMC and feature DX11, multi-screen Eyefinity and GPGPU compute technology. There's not a whole lot more you can cram in without an architecture redesign and, relatedly, a shift to a smaller manufacturing process.

For various reasons that are outside the scope of this review, AMD has not been able to transition to a smaller process for these chips. A 28nm node and new architecture are both coming, but, and this is important, the sub-£80 Radeon HD 6K GPUs are practically identical to their 18-month-old brethren.

Let's spell it out with ye old table.

HD 6450
HD 6570
HD 6670
HD 5670
HD 5770
HD 6790
GT 440
GTS 450
GTX 550 Ti
Transistors 0.37bn 0.72bn 0.72bn 0.63bn 1.04bn 1.75bn 0.59bn 1.17bn 1.17bn
Die size Unknown Unknown Unknown 104mm² 170mm² 255mm² 116mm² 238mm² 238mm²
General clock 750MHz 650MHz 800MHz 775MHz 850MHz 840MHz 810MHz 783MHz 900MHz
Shader clock 750MHz 650MHz 800MHz 775MHz 850MHz 840MHz 1,620MHz 1,566MHz 1,800MHz
Memory clock 3,600MHz 4,000MHz 4,000MHz 4,000MHz 4,800MHz 4,200MHz 3,200MHz 3,608MHz 4,104MHz
Memory size 1,024MB GDDR5 1,024MB GDDR5 1,024MB GDDR5 1,024MB GDDR5 1,024MB GDDR5 1,024MB GDDR5 1,024MB GDDR5 1,024MB GDDR5 1,024MB GDDR5
Memory interface 64-bit 128-bit 128-bit 128-bit 128-bit 256-bit 128-bit 128-bit 192-bit
Memory bandwidth 28.8GB/s 64GB/s 64GB/s 64GB/s 76.8GB/s 134.4GB/s 51.2GB/s 57.7GB/s 98.5GB/s
Shaders 160 480 480 400 800 800 96 192 192
GFLOPS 240 724 768 620 1,360 1,340 311 601 691
Texturing 8ppc bilinear
4ppc FP16
24ppc bilinear
12ppc FP16
24ppc bilinear
12ppc FP16
20ppc bilinear
10ppc FP16
40ppc bilinear
20ppc FP16
40ppc bilinear
20ppc FP16
16ppc bilinear
16ppc FP16
32ppc bilinear
32ppc FP16
32ppc bilinear
32ppc FP16
ROPs 4 8 8 8 16 16 4 16 24
ROP rate 3.0 5.2 6.4 6.2 13.6 13.4 3.2 12.5 21.6
GTexel/s bilinear 6 15.6 19.2 15.5 34 33.6 13 25.1 28.8
FP16 rate 3 7.8 9.6 7.8 17 16.8 6.5 25.1 28.8
Power connectors None None None None 6-pin 6-pin + 6-pin None 6-pin 6-pin
Board power (TDP) 27W 60W 66W 64W 108W 150W 65W 106W 116W
Retail price £35 £55 £75 £75 £90 £105 £50 £85 £110

Analysis - HD 6450

The three new GPUs line the left-hand side. We've thrown in a Radeon HD 5670 next to the HD 6670 for comparison's sake. Radeon HD 6450 is the cheapest of the trio and goes by the codename of Caicos. It's based on a distinct core that has 370m transistors. We've listed the top-line configuration and speeds and feeds, though AMD is to make it available to retail partners with various core and memory frequencies - 625MHz - 750MHz core and either DDR3 or GDDR5 memory.

A 27W TDP will enable partners to cool the GPU passively, and we expect to see the majority of retail cards sport a half-height form factor and a large, fan-less heatsink.

Analysis - HD 6570

AMD drops the two 5550/70 parts and simplifies down to a single card - the 'Turks' HD 6570. A second version will be available with the same specs but with DDR3 memory instead of GDDR5, reducing bandwidth by more than half, though this is offset with a drop of the TDP from 60W to 44W.

Analysis - HD 6670

Assuming this card is a like-for-like replacement of the HD 5670, which seems a reasonable assumption, the new GPU receives a slight bump in core speed, shading and texturing cores jump by 20 per cent, but the memory throughput remains the same. A direct consequence of adding in more cores and TMUs is a larger die than HD 5670's, to the tune of an additional 90m transistors. In fact, the specifications indicate that the HD 6670 is not much more than a faster-clocked HD 6570 GDDR5 card.

So, generalising massively, the new GPUs will offer, say, around 10 per cent more performance than the 18-month-old cards they replace. Doesn't seem like much of a gain, does it? But AMD is keen to promote the non-gaming enhancements, so here they are.

6K vs 5K - multimedia benefits

Caicos- and Turks-based Radeons have the latest video-logic block, UVD 3. Compared to the last generation this brings DisplayPort v1.2, HDMI 1.4a, and hardware-based acceleration for Multi-View (MVC, Blu-ray 3D) DivX and Xvid codecs. We suppose this is really where AMD is putting the efforts, for any sub-£80 GPU cannot be considered a proper gaming card.

The HD 6670 also extends Eyefinity coverage from three to four screens - two have to use a DP v1.2 splitter - which may be of benefit for users looking to add more pixels and screen real estate for a relatively small additional outlay.

First-page summary

AMD's three mainstream GPUs are incremental improvements over well-established Radeon HD 5-series technology. A little extra performance and an enhanced multimedia feature-set provide a tenuous base on which jump generations and nomenclature.