New mainstream and enthusiast Radeons

AMD's add-in board (AIBs) partners have stood by impatiently as archrival Nvidia has launched four new desktop graphics cards over the summer. Based on the energy-efficient Kepler architecture, GeForce GTX Titan, 780, 770, and 760 have improved the green team's performance at the serious end of the market, with partners releasing a roster of retail cards in the GTX wake.

Announced on September 26, AMD has come back swinging with gusto. Six Radeon GPUs have been unveiled, providing much-needed impetus to partners, and AMD has seen fit to change the naming convention along the way. Quite a mouthful, the Radeon R9 290X, R9 290, R9 280X, R9 270X, R7 260X, and R7 250 cards are busy being packed into containers destined for your favourite retailers.

Now, while we'll get onto nomenclature in a moment, the R9 290X and 290 are being officially released at a later date. These are brand-new GPUs designed to compete against the ultra-powerful GeForce GTX Titan and 780 cards. The remainder, however, should be available from today onwards, meaning four new GPUs for the likes of Sapphire, Asus, MSI, et al, to get their teeth stuck into.

R9 and R7 what?

AMD has sampled the press with a trio of X-rated cards - namely the R9 280X, R9 270X and R7 260X. The names bear little correlation to previous Radeon branding, so let's first take a moment and help explain AMD's thinking.

Taking the R9 280X as an example, the 'R' denotes Radeon, '9' the market segment (higher is better), '2' the generation, '8' the position occupied by the particular GPU in the generation (higher is better), and an optional 'X' that flags the card as the fastest variant. R9 280X, then, is an enthusiast card of what is now termed the second generation. It sits high in the overall stack because it is only bettered by the R9 29x cards.

Generalising heck of a lot, R9-type cards should be able to run the latest games at 2,560x1,440-resolution settings with eye candy turned all the way up, while R7 cards are well-suited for 1,920x1,080 (full-HD) gaming with decent image quality. The subsequent nomenclature dictates just how well a particular card is able to meet this overarching definition, but you get the picture, we hope.

And The Great Rebrand of 2013

OK, so we have brand-new cards based on next-generation silicon, right? The as-yet-unreleased R9 290X and R9 290 are certainly distinct from any Radeons that we've seen before - they really need to be, in order to mix it up with the Tesla-derived GeForce GTX Titan and 780 - but the remaining cards are, for the most part, a rebrand of existing Radeons.

The following table lists the R9 280X, R9 270X and R7 260X alongside their closest relatives in the current 7-series line-up. Take a minute or two to cross compare.

GPU Radeon R9 280X 3GB Radeon HD 7970 GHz 3GB Radeon R9 270X 2GB Radeon HD 7870 2GB Radeon R7 260X 2GB Radeon HD 7790 1GB Launch date October 2013 June 2012 October 2013 March 2013 October 2013 March 2013 DX API 11.2 11.1 11.2 11.1 11.2 11.1 Process 28nm 28nm 28nm 28nm 28nm 28nm Transistors 4.3bn 4.3bn 2.8bn 2.8bn 2.08bn 2.08bn Approx Die Size 352mm² 352mm² 212mm² 212mm² 160mm² 160mm² Processors 2,048 2,048 1,280 1,280 896 896 GPU Boost None AMD-specific None None None None Texture Units 128 128 80 80 56 56 ROP Units 32 32 32 32 16 16 GPU Clock/Boost (MHz) 1,000 1,000 (1,050) 1,050 1,000 1,100 1,000 Shader Clock/Boost (MHz) 1,000 1,000 (1,050) 1,050 1,000 1,100 1,000 GFLOPS 4,096 4,096 2,688 2,560 1,971 1,792 Memory Clock (MHz) 6,000 6,000 5,600 4,800 6,400 6,000 Memory Bus (bits) 384 384 256 256 128 128 Max bandwidth (GB/s) 288 288 179.2 153.6 102.4 96 Power Connectors 8+6-pin 8+6-pin 6+6-pin 6+6-pin 6-pin 6-pin TDP (watts) 250 250 180 175 115 85 GFLOPS per watt 16.38 16.38 14.93 14.63 17.14 21.08 TrueAudio DSP No No No No Yes No Current price $299 $399 $199 $199 $139 $129/$139

Architecture analysis - R9 280X

Scanning the first two columns reveals that the R9 280X is almost identical to the incumbent Radeon HD 7970 GHz Edition (GE) from an architectural standpoint. In fact it should be marginally slower as its core speed runs at a maximum 1,000MHz, compared a possible 1,050MHz for the core-boosting HD 7970 GE. This means AIBs with stock of HD 7970 GE GPUs, or any qualified Tahiti parts, can generally relabel them as R9 280Xs, creating a 'brand-new' card from thin air: nomenclature changes masking the recycling of technology.

The key difference between the two parts is price. Stock-clocked R9 280X cards are set to be around $100 cheaper, at $299 (£230). It's this reduced pricing that's the headline here, not the technology, so having the very best of the last generation available at this price point is sure to put pressure on Nvidia's performance-equivalent cards.

AMD says that the passage of time and TSMC's - the Radeon manufacturing partner - process improvements have enabled the base Tahiti architecture to be uplifted in terms of speed. The R9 280X is the only Tahiti-class GPU being released, and achieving a core speed of 1,000MHz is now relatively easy. Perhaps, then, it's better to think of the R9 280X as a Tahiti card as opposed to a direct Radeon HD 7970 GE replacement.

Architecture analysis - R9 270X

Hey, if the rebranding trick works on the one card why not use it again? The R9 270X uses the same Pitcairn XT silicon as the presently-available Radeon HD 7870. AMD provides a little extra performance by increasing the core frequency by 50MHz and GDDR5 memory by an effective 800MHz. Overall performance should go up by around 10 per cent, we imagine, so the $199 (£150) price looks good. A second version, equipped with 4GB of memory, is to be made available from $229 (£170).

Architecture analysis - R7 260X

Three time's the rebranding charm, folks! The R7 260X is a faster-clocked version of the Radeon HD 7790 (Bonnaire XT) that's been doing the review rounds for the last six months. Now outfitted with 2GB of GDDR5 memory as standard, R7 260X will come in at $139 (£110) or so, matching the price of the slower-clocked HD 7790 2GB.

Upgrades to R-series GPUs - outputs, TrueAudio, DX 11.2

Perhaps we're being unkind in liberally using the term rebrand. AMD's finally improved the display-output mechanism by enabling both HDMI ports to be used in conjunction with HDMI - 7-series cards couldn't run all three due to sharing a clock generator between two digital outputs. Getting into detail, the cards use an updated firmware that enables three screens from the three outputs. We note that, in a different way, AIBs such as Sapphire have already circumvented this silly obstruction with its FLeX cards.

AMD's debuting a new hardware technology called TrueAudio on select new GPUs. Though we'll go into the technicalities in the R9 290 and 290X reviews in due course, TrueAudio is a digital signal processor (DSP) that, AMD says, offloads complex audio calculations from the GPU.

Game developers haven't historically been eager to include complex audio in games because of the potential performance hit on framerate, and while a DSP make sense - Creative and Aureal have championed them before - the success of TrueAudio is only likely to be heard (excuse the pun) if AMD can convince enough middleware vendors and developers to code for its nascent technology.

It's therefore interesting that the only GPU in our line-up imbued with TrueAudio is the R7 260X; on first glance, there's little reason, other than cost, for it not to be present on the higher-specified cards, but AMD has gone on record as saying that newer features, such as TrueAudio HD, are typically implemented into new GPUs. The R7 260X, based on Bonnaire, is simply more recent than Tahiti or Pitcairn XT and is therefore the logical recipient of newer technology.

But the TrueAudio IP block is part of the GPU silicon, not a separate chip, so, reading between the lines, it cannot be readily implemented into existing GPUs. The very fact that it's on the Bonnaire-class GPU actually means it's been baked in from the get-go. In other words, Bonnaire GPUs, manufactured months ago, may well have been sold with this new TrueAudio feature under cover and disabled.

Oh, and did you catch the DX 11.2 upgrade? Part of upcoming Windows 8.1 (though not standard 8) and the Xbox One console, DX 11.2, as the name suggests, brings with it incremental improvements to the application programming interface. Chief amongst these is a feature known as tiled resources, where system and graphics memory can be used to hold high-quality textures, rather than on the graphics framebuffer alone. The DX 11.2 spec is only software-supported by the cards being released today; you will have to wait until the R9 290 and R9 290X to have hardware support (read better performance).

Summary

Focussing on the three X-branded cards in the new R-series line-up shows that, aside from minor changes, they are the same as the now-redundant 7-series GPUs which have been available for some time now. It would have perhaps been foolish to expect AMD to launch an entire new architecture in one fell swoop, sub-divided into numerous cards, so a little silicon finagling and lower street prices suffices for now. The real acid test for AMD is how the upcoming R9 290 and R9 290X compare against the best Nvidia has to offer, but that's another story for another day.