The most powerful Nvidia-based card we’ve tested is the GTX 970. Nvidia originally pitched the GTX 970 as a die-harvested derivative of the flagship GTX 980 – this means the company would re-use chips that weren’t able to run at full GTX 980 speeds for the less powerful model, rather than let them go to waste. The GTX 970 was understood to have three fewer streaming processors than the GTX 980, meaning fewer texture units and a slower core clock speed, but otherwise retain the same 4GB of GDDR5 memory and 2MB of L2 cache for accessing it. However, it turns out an error in the specification tables that went out to reviewers and board partners means this isn’t the case.
Instead, one of the GTX 970’s four memory controllers is only partially enabled, meaning only 1.75MB of the L2 cache is switched on. As a result, the video memory is split between a high-performance segment containing 3.5GB and a low-performance segment with the remaining 512MB. The low-performance segment is significantly slower to access than the high-performance segment, hampering performance.
In practical terms, however, applications see the full 4GB of RAM and the video driver balances out the load. Only after the first 3.5GB is requested, to fill up the entire high performance segment, will the 512MB segment get used. At this point, Nvidia’s video driver attempts to put the least important data in the slower segment. Although the final 512MB is much slower than the high-performance segment, it is still fast enough for the graphics card to use it rather than rely on swapping data with system RAM.
Despite this specification stumble, however, the GTX 970 is still a seriously powerful GPU. The reference design has 1,664 CUDA cores running at 1,050MHz, boosting up to 1,178MHz when thermal limits allow. The 4GB of GDDR5 memory runs at 1,750MHz, operating on a 256-bit memory bus. The underlying GM204 GPU core has much in common with the GTX 980, except here it consumes less power as part of the chip is disabled. As with other cards that use the Maxwell architecture, the GTX 970 is surprisingly power-efficient, only drawing 145W when playing the most demanding games.
|Card||Rating||Award||Price inc VAT||Supplier|
|Asus GTX 970 DC Mini||4||£297||www.dabs.com|
|Asus STRIX GTX 970 DirectCU II||4||Recommended||£285||www.ebuyer.com|
|MSI GTX 970 Gaming 4G||4||£280||www.ebuyer.com|
|Zotac GTX 970 AMP! Extreme edition||3||£330||www.novatech.co.uk|
As with the rest of Nvidia’s range, it’s next to impossible to buy a GTX 970 with a reference cooler, or one using the reference clock speeds. Both Asus and MSI have used twin-fan designs that are highly effective at cooling the GTX 970. Asus has used the extra cooling headroom to overclock the Asus STRIX GTX 970 DirectCU II to 1,203MHz, and increase the boost clock to 1,355MHz. This helped it score 116.8fps in Dirt Showdown, 77.8fps in Tomb Raider and 44.7fps in Metro: Last Light Redux at 1,920×1,080 with Ultra and Very High detail settings.
All three games are easily playable at these frame rates. The card had no problem with Dirt Showdown or Tomb Raider once we increased our test resolution to 2,560×1,440, and we saw a smooth 49.7fps average in Metro once we disabled SSAA. Dirt Showdown was even playable at 3,840×2,160 with Ultra quality settings, with 48fps, and we saw a just-playable 29.9fps in Tomb Raider at this resolution once we swapped SSAA for FXAA. The card managed around 32fps in Metro after we’d dropped detail levels to High.
If you’re after an Nvidia GTX 970, the Asus STRIX is a quick model and is worth the extra fiver over MSI’s GTX 970 for a modest performance increase. However, you can get similar performance from the XFX AMD Radeon R9 290 for around £40 less, or a quicker card for similar money with the Sapphire VAPOR-X R9 290X.
MSI’s GTX 970 Gaming 4G has a slightly less aggressive overclock, running at 1,140MHz and boosting to 1,279MHz. 115.5fps in Dirt Showdown is almost twice what we would deem playable, while 80.3fps in Tomb Raider and 46fps in Metro: Last Light were also excellent results. As with the Asus STRIX GTX 970 card above, there’s enough headroom to increase the resolution to 3,840×2,160 in some games, and 2,560×1,440 in others – the MSI card is very slightly slower, but only by a frame or two. The Asus STRIX remains our favourite GTX 970 card, however, and AMD’s top-end cards are still better value.
In terms of customisations, Zotac’s GTX 970 AMP! Extreme edition goes even further than the MSI and Asus cards, replacing the reference cooler with a massive three-fan system. It’s the fastest GTX 970 we’ve seen out of the box, with a 1,203MHz GPU core clock and 1,355MHz boost clock, as well as memory overclocked to 1,800MHz. This helped the card achieve impressive scores of 118.9fps in Dirt Showdown, 82.7fps in Tomb Raider and 47.5fps in Metro: Last Light, putting it towards the top of the performance charts, but there’s a lot of headroom for pushing it further. All the power circuitry has been upgraded over the reference design and a microUSB port is built onto the card for extreme overclocking through the Windows desktop.
This is the fastest GTX 970 card we’ve seen, but all this performance comes at a price. We don’t think the Zotac’s extra few frames are worth the extra £50 over the other GTX 970 cards, and compared to the faster Sapphire VAPOR-X R9 290X it starts to look like poor value.
The Asus GTX 970 DC Mini is designed specifically for Mini-ITX gaming PCs and home theatre systems, and Asus has managed to reduce the length of the card to just 170mm. The single fan might have to work a little harder, and make slightly more noise than cards such as the Asus STRIX GTX 970, but scores of 118.2fps in Dirt Showdown, 77.3fps in Tomb Raider and 44.8fps in Metro: Last Light suggest this card would be overkill for a 1,920×1,080 display. As with the other GTX 970 cards, gaming at 2,560×1,440 is possible in the most demanding titles at sky-high detail levels, and 3,840×2,160 gaming is on the cards if you reduce detail levels slightly.
If you need the ultimate card for a compact gaming PC, the Asus GTX 970 DC Mini is the one to have; it’s much more expensive than the Sapphire R9 285 2GB GDDR5 ITX Compact Edition, but also much more powerful.
|Model||GTX 970 DC Mini||STRIX GTX 970 DirectCU II||GTX 970 Gaming 4G||GTX 970 AMP! Extreme edition|
|Slots taken up||2||2||2||2|
|GPU||Nvidia GeForce GTX 970||Nvidia GeForce GTX 970||Nvidia GeForce GTX 970||Nvidia GeForce GTX 970|
|GPU clock speed||1,088MHz||1,203MHz||1,140MHz||1,203MHz|
|GPU clock boost speed||1,228MHz||1,355MHz||1,279MHz||1,355MHz|
|Memory||4GB GDDR5||4GB GDDR5||4GB GDDR5||4GB GDDR5|
|Max memory bandwidth||224.4GB/s||224.4GB/s||224.4GB/s||230.4GB/s|
|Graphics card length||170mm||283mm||264mm||300mm|
|Mini HDMI outputs||0||0||0||0|
|Mini DisplayPort outputs||0||0||0||0|
|Power leads required||1x 8-pin PCI Express||1x 8-pin PCI Express||1x 6-pin PCI Express, 1x 8-pin PCI Express||2x 8-pin PCI Express|
|Accessories||DVI to VGA adaptor||DVI to VGA adaptor||DVI to VGA adaptor||DVI to VGA adaptor, 2x twin Molex to 8-pin PCI Express adaptors, Mini USB to internal USB header cable|
|Price including VAT||£297||£285||£280||£330|
|Warranty||Three years RTB||Three years RTB||Three years RTB||Five years RTB|
|Part code||GTX970-DCMOC-4GD5||STRIX-GTX970-DC2OC-4GD5||GTX 970 GAMING 4G||ZT-90103-10P|