AMD’s Radeon HD 6670 & Radeon HD 6570: Two’s Company, Sub-$100’s A Crowd

Two weeks ago we saw the paper launch of the Radeon HD 6450, the low-end member of AMD’s Northern Islands family of GPUs. It was a solid product for HTPC use and a very notable improvement over the 5450 it replaced, but it was an uncharacteristically delayed launch for AMD. At the same time we noted that the Northern Islands family had one more GPU we had not seen: Turks.

As it turns out, Turks-based video cards will be launching alongside the 6450 today, delivering all of the remaining Northern Islands products in a single push. Turks will be powering the Radeon HD 6670 and Radeon HD 6570, replacing the Redwood-based Radeon HD 5670 and Radeon HD 5570 respectively. Considering that we saw AMD deliver a solid update for their low-end lineup with the 6450, will we see the same with Turks and the 6670/6570? Let’s find out.

Turks is the 4^th and final member of the Northern Islands family, or to be more practical the 3^rd and final member of the revised Evergreen family. Based on Redwood before it, Turks implements the Northern Islands series’ architectural improvements while also implementing a larger number of SIMDs in order to give AMD a mid-cycle performance boost on the same TSMC 40nm process.  With the 6450 dragging up the low-end of the market and competitive pressure from NVIDIA, AMD needed a product above the 5670 but still smaller/cheaper than the 5750, and that is what Turks will provide.

Architecturally, Turks is very close to Redwood. Compared to Redwood it has 6 SIMDs instead of 5 SIMDs, giving it 480 SPs and 24 texture units versus 400 SPs and 20 texture units on Redwood. The ROP count remains unchanged at 8 ROPs, while the memory bus is still 128 bits wide. Of course being a Northern Islands GPU, Turks implements all of the common improvements we see with NI: UVD3, improved texture filtering, HDMI 1.4a (e.g. Blu-Ray 3D), a revised tessellation unit, and DisplayPort 1.2 support.

These improvements have of course added some bulk to the die; Redwood was comprised of 627 million transistors while Turks is 716M. This in turn has increased the die size slightly to 118mm2, coming from 104mm2 on Redwood. Power consumption has also gone up accordingly, but less so than the transistor count or die size did. For the 6670 the TDP is 66W, versus 60W for the 5670. The 6570 GDDR5 meanwhile is rated for 60W versus 43W for the 5570; this is largely a consequence of switching to GDDR5. Meanwhile idle power consumption is 10W for the 6570 DDR3, 11W for the 6570 GDDR5, and 12W for the 6670.

As far as performance is concerned, the 6670 is close to the 5670 on paper. At 800MHz the 6670 has a 25MHz (3%) core clock advantage, while the 1GHz (4GHz data rate) memory clock is identical to the 5670. The big advantages for the 6670 are any gains in architectural efficiency, combined with the additional SIMD; the SIMD alone gives the 6670 a 20% shading and texturing improvement over the 5670. With the same 8 ROPs between the two cards, the 6670 should excel in shading and texturing bound situations, while ROP or memory bandwidth bound situations will be much closer.

Top: Radeon HD 6670. Bottom: Radeon HD 6570

For the 6570 on the other hand, the performance advantage is quite a bit larger. The original 5570 – and the one we continue to test today – launched with DDR3 memory. AMD did introduce a GDDR5 variant in the summer of 2010, but it never gained much traction. So compared to the 5570, the GDDR5 6570 with its 1GHz (4GHz data rate) GDDR5 has 222% the memory bandwidth of the DDR3 5570 and its 900MHz (1.8GHz data rate) RAM. Now there’s a catch in all of this: similar to how the 5570 ended up, AMD will be launching cards with both GDDR5 and DDR3. The GDDR5 cards like the one we’re reviewing today will come with 512MB of RAM, while the DDR3 cards will come with 1GB of RAM. The extra RAM has its advantages in some edge cases, but our advice always has been and remains to be that you should pick the GDDR5 versions of most video cards over the (G)DDR3 versions. The only notable downside to the GDDR5 card in this case is that GDDR5’s power consumption is much higher, which is why the GDDR5 6570 is a 60W card while the DDR3 6570 is 44W.

RAM aside, the 6570 has the same advantages over the 5570 as the 6670 has over the 6570. With identical core clocks of 650MHz, the performance difference comes down to the RAM, followed by the 20% increase in the SIMD count. The GDDR5 6570 should outperform the DDR3 5570 by quite a bit at all times, but it’s going to absolutely shine in memory bandwidth or shader-bound situations, while anything that’s ROP-bound will be closer.

AMD will be launching the 6670 at $99 and the 6570 at $79, putting both cards right in the middle of the highly-competitive sub-$100 market. Competing cards include the Radeon HD 5670, the frequently discounted to $99 Radeon HD 5770, the similarly discounted GeForce GTS 450, and the GeForce GT 440 – a higher clocked GF108 (GT 430) part with GDDR5 that NVIDIA quietly released back in February. As was the case with the 6450 and most other sub-$100 launches, without a die shrink new parts cannot compete with discounted parts from a higher tier, so it shouldn’t come as a surprise that the 6670 in particular is easily beaten on performance at $99.

Thankfully unlike the 6450, the 6670 and 6570 are hard launching today. They will be appearing at e-tailers later today alongside the 6450.