AMD Radeon HD 6450 Review: Caicos Cometh

AMD populates the entry-level tier with its new Radeon HD 6450, based on the Caicos graphics processor. Does this board have what it takes to stand out in the crowded sub-$100 market and vie for a spot in your next home theater PC?

Hot on the heels of its Radeon HD 6790, AMD is releasing another new graphics card today. This time, the target is the sub-$60 price range, bringing Radeon HD 6000-series features to the entry-level market. Meet the Radeon HD 6450.

Low-end graphics cards account for the bulk of sales, and that means competition; the Radeon HD 5450, Radeon HD 5550, GeForce GT 220 and GeForce GT 430 are only a few of the models that you'll have to consider if you're looking for alternatives. Before we compare them, let’s see what this new Caicos GPU has to offer:

So, this card's Caicos core is based on the same architecture that we first saw in the Barts GPU, which drivesthe Radeon HD 6800-series cards. The new model is far less complex, with only one-seventh of the Radeon HD 6870’s compute resources. Instead of 14 SIMD engines, the Caicos has two, each containing four texture units and 16 stream processors. With 5 ALUs per stream processor (yes, we're still talking about the older VLIW5 design, not the newer VLIW4 arrangement featured on Cayman), the resulting total is 160. These are coupled to a single render back-end with four color ROPs, attached to a lone 64-bit memory controller.

It’s as though AMD paid close attention to our Radeon HD 5450 review in February of 2010, where we said: “It is unfortunate that that the SIMD engines have been cut in half compared to the GPUs found on… …higher models that sport a more robust 16 stream processors per.” Each of Caicos’ SIMDs sport the same specifications as Barts', so we can expect a sizable performance gain over the Radeon HD 5450.

But that’s not the only improvement. The Radeon HD 6450 comes in two flavors of memory technology: DDR3 and GDDR5. Since GDDR5 memory doubles the theoretical throughput of DDR3, given the same base clock, this option should compensate for the narrow 64-bit memory interface.

Finally, like all products in the Radeon HD 6000 family, this latest model improves tessellation performance, includes Eyefinity enhancements, and, of course, features UVD 3, including the ability to accelerate Blu-ray 3D video over HDMI 1.4a.

Now that we have a good idea how powerful the Radeon HD 6450 should be, let’s take a closer look at the playing field:

	Radeon HD 5450	Radeon HD 6450	Radeon HD 5550	GeForce GT 220	GeForce GT 430
Shader Cores:	80	160	320	48	96
Texture Units:	8	8	16	16	16
Color ROPs:	4	4	8	8	4
Fabrication process:	40 nm	40 nm	40 nm	40 nm	40 nm
Core/Shader Clock:	650 MHz	625 MHz DDR3 750 MHz GDDR5	550 MHz	625/1360 MHz	700/1400 MHz
Memory Clock:	400 MHz DDR2 800 MHz DDR3	533-800 MHz DDR3 800-900 MHz GDDR5	900 MHz DDR3	790 MHz DDR3	900 MHz DDR3
Memory Bus:	64-bit	64-bit	128-bit	128-bit	128-bit
Memory Bandwidth:	6.4 GB/s DDR2 12.8 GB/s DDR3	8.5-12.8 GB/s DDR3 25.6-28.8 GB/s GDDR5	28.8 GB/s DDR3	25.3 GB/s DDR3	28.8 GB/s DDR3
Thermal Design Power (W)	19.1 W (typical)	20 W DDR3 27 W GDDR5 (typical)	40 W (maximum)	58 W (maximum)	42.7 W (maximum)

We can see a clear evolution from the Radeon HD 5450 and Radeon HD 6450,, with only the number of stream processors doubled. This should enable a quantifiable performance difference, though. And when it's equipped with GDDR5, the new card should serve up modest gaming results.

The Radeon HD 5550 is far more interesting competition. It essentially doubles all of the Radeon HD 6450’s specifications: 320 shader processors, 16 texture units, and 8 ROPs operating on a 128-bit memory interface. Although the GDDR5-equipped version of the 6450 might match the older board's memory bandwidth, its higher core clock does not compensate for its resource deficiency. Of course, the Radeon HD 5550 doesn’t support Blu-ray 3D decode acceleration, though it is capable of playing back this format over HDMI 1.4a. It simply relies on more host processing to power through the decode pipeline.

The GeForce GT 220 DDR2 is also priced similarly to the Radeon HD 6450 GDDR5, and while it sports a powerful GPU and a 128-bit memory interface, it is crippled by slower DDR2 memory. Ironically, despite Nvidia’s lead in 3D alacrity, this card is not capable of playing back Blu-ray 3D over HDMI. The GeForce GT 430 is Nvidia’s lowest-end card capable of this feat, and it typically costs about $70 (although a couple models can be found for $10 cheaper than that online). Indeed, with twice as many shader cores as the GT 220, the GeForce GT 430 may offer the strongest competition for the 6450 on both the HTPC and gaming fronts.