AMD Completes Its GCN Lineup With Impressive Mid-Range 7850/7870 Cards

Advanced Micro Devices, Inc. (AMD) today pushed out yet another graphics processing unit design.  This hard launch means that the chipmaker has produced 3 launches in the last 3 months — an alacritous release pace, to be certain.  

There are plenty of pressing questions surrounding the latest launch — the 78xx series.  How does it perform?  Does it suffer the same overpricing issues as its most recent Southern Islands predecessor?  

But for a moment AMD’s critics and proponents alike should pause and appreciate the solid launch it has put together at the 28 nm node.

I. Meet Pitcairn

The latest hardware, unsurprisingly, is the Radeon HD 7850 and 7870.  Code-named Pitcairn, after the tiny British island located far to the west of Chile in the South Pacific, the 78xx cards join the lower-range Radeon HD 7750/7770 and the high-end Radeon HD 7950/7970.

With the latest addition Southern Islands — the lineup that introduced AMD’s new GPU-computing-friendly “Graphics Core Next” architecture — finally feels like a true family.  And there’s a nice symmetry to the offerings.  If you take the Radeon HD 7750, 7850, and 7950, each step bumps the core count by a factor of two; likewise for the Radeon HD 7770, 7870, and 7970.  For those interested, the ’50 cards are dubbed “Pro” in their extended code-names, while the ’70 cards are dubbed XT.

Pricing is also rather periodic, with each model towards the higher end commanding an extra $100 USD.  The family members, from Radeon HD 7750 to Radeon HD 7970, are priced at $109, $159, $250, $350, $450, $550.

While everyone appreciates new technology, buying it is a distinctly different tale.  To sell, graphics cards must be priced right.  

The $250 USD Radeon HD 7850 falls somewhere between rival NVIDIA Corp.’s (NVDA) GeForce GTX 560 Ti and Geforce GTX 570 in price.  The GTX 560 Ti is currently $200 USD at best, while the GeForce GTX 570 can be found for $305 USD.  Price-wise, the card is closest to NVIDIA’s lesser known GTX 560 Ti 448 Cores, a GPU computing-centric card with 14 SMPs, which retails for $270 USD.

The new Radeon HD 7850 from AMD [Image Source: Tech Report]
Meanwhile the $350 USD Radeon HD 7870 HD has a tougher lot in life, falling midway between the aforementioned GeForce GTX 570 ($305 USD) and the $415 USD GeForce GTX 580.

In other words, 7800 series cards are priced at a rather interesting pair of points, directly straddling its rival’s major prices.  So do the cards split the difference in performance between the GeForce high and low comparables, the bear minimum to recommend a purchase?

II. The Specs, and First Thoughts

Let’s find out, beginning with the specs (past generations and other Radeon HD 7xxx series models included, for comparison).

General1 2

In power and temperatures Pitcairn and its peers are model citizens, easily outdoing their hot, power hungry predecessors.  This shows the merits of the move to the 28 nm process, but may be disappointing (a bit) to those hoping that the new architecture would bring an even greater leap downwards.  You won’t find miracles here, but things have improved slightly.  

Noise is somewhat of a holding pattern as the cooler is still similar to the last generation.  OEM cards will obviously vary greatly in terms of noise (and temperature), as past generations have shown.  The good news here, is that the already low base temperatures in the somewhat noisy stock cooler, mean that likely you will be able to find a quieter OEM solution, hence winning on all fronts — power, temperature, and noise. 

While the Radeon HD 78xx series is seemingly a successor to the Radeon HD 68xx (Barts) in name and core count, its transistor count and price hint that its true comparable is the Radeon HD 69xx SKUs (Cayman), hence we’ll use that comparison, from here on out. (If you prefer a comparison to the Radeon HD 68xx, you can jump to Wikipedia‘s tables.)
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(1 “Real world” Power, Noise, and Temperature levels taken courtesy of AnandTech)
(2 All 7000 series GPUs are produced on processes by Taiwan Semiconductor Manufacturing Comp., Ltd. (TPE:2330).)

  In general terms the latest GCN cards — like their Southern Islands peers offer less of almost everything, at least at face value.  Core counts, texture units, etc. are all chopped down.  However, the increased transistor count hints that the smaller counts may be more due to differences in how these units are structured in the GCN architecture.  

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Thus reserve your judgment until we come to actual real world performance — AMD’s older Terascale 2 (Radeon HD 5xxx, 6xxx series) architecture is not an apples and oranges comparison to the new and different Graphics Core Next (GCN) architecture.

In Graphics Core Next’s architecture (see below) cores are arranged in blocks called “Compute Units” (CUs).  Each compute unit packs 64 stream processors and 4 texture units.  The 7800 cards use the same 4 CU block as the 7900 cards.  The Radeon HD 7850 has 4 such blocks, while the Radeon HD 7870 has five.  Each 4 CU block has its own L1 instruction and an L1 read-only cache (NVIDIA CUDA users will recognize this as similar to constant memory). 

A 512 KB L2 cache pool is shared by all the CU blocks, which works out to 32 KB per CU on the Radeon HD 7850 and 25.6 KB per SP on the Radeon HD 7870.  This sounds worse than NVIDIA’s Fermi architecture from a compute perspective as Fermi currently offers 48 KB per computing unit.  However, it’s important to consider than even the compute-centric GeForce GTX 560 Ti 448 Cores only has 14 streaming multiprocessors (SMPs).  In other words, AMD’s CU is a bit smaller than NVIDIA’s SMP and has a bit less memory — but AMD has more CUs in comparable cards.


Versus the 7900 series, which received a nice memory bump, the 7700 series sees a small drop in memory clock, which affects the bandwidth.  FP64 performance is also more limited that in the previous generation.

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III. Real World Performance Reports, New Features

Aside from its stock performance AMD’s new cards do offer some nice perks.  Among the biggest is support for Direct3D 11.1, which will air inside the upcoming Windows 8.  PowerTune and Fast HDMI are appreciated perks as well, with the former allowing easier power management and the latter allowing faster connections to your displays.  The new Video Codec Engine (VCE) is supported, but AMD has yet to deliver this feature, which looks relatively exciting, in providing acceleration for standard video codecs.

Performance wise, Pitcairn looks very good, based on AnandTech‘s thorough benchmarking.  In most titles the Radeon HD 7850 trades blows with the GeForce GTX 570, while the Radeon HD 7870 is competitive with the GeForce GTX 580.  The cards tend to perform better at higher resolutions, but are overall right where AMD wants them to be — nearing the performance of its competitors’ cards that are currently $55 USD or more extra.

The Radeon HD 7870 outperforms the GeForce GTX 580 on The Elder Scrolls V: Skyrim, on “ultra” settings. [Image Source: GameRant]
This is a strong turn around from the Radeon HD 77xx launch, which saw AMD struggling to justify the higher price point of cards that lost, in many cases, to cheaper NVIDIA cards.  It’s consistent, though with the initial Radeon HD 79xx, which saw high prices — but also a new industry high-mark in single-card performance.

IV. To Buy?

With the Radeon HD 79xx launch AMD gave gaming high-end enthusiasts notice — buy AMD or buy an inferior card/wait months for an alternative.  

With the Radeon HD 77xx launch, AMD’s pricing was laughably bad.  There was really no reason for budget buyers to even consider the card, unless they were hugely biased AMD/Radeon fans.

The Radeon HD 78xx launch sees a return to pricing that may leave one a bit unsatisfied, but which at least can’t be beat by anything in the current field.  At the end of the day AMD’s $250 USD Radeon HD 7850 card performs close to NVIDIA’s $305 USD card, and AMD’s $350 USD Radeon HD 7870 performs close to NVIDIA’s $415 USD card.

In other words, Pitcairn is a winner.  If you’re in the market for a $250-300 or $350-400 USD card, you should consider these models your best buy.

AMD has done well to get a head start on NVIDIA.  NVIDIA’s 600/700 (Kepler) series announcement is rather tardy.  At this point AMD is capitalizing on the mid-to-high end.  That’s both good and bad news for enthusiast gamers — good news because they get superior product, bad news because they suffer higher prices.

On the other hand, reportedly yield difficulties are contributing to AMD’s poor pricing on the bottom end.  The Radeon HD 7850 and Radeon HD 7750 are night and day in terms of bang for your buck.  The former card is a great deal — the latter is a horrid deal.

In terms of general profits, high-volume parts often drive a major percentage of total revenue.  Thus NVIDIA may not be suffering that much, even with Kepler missing-in-action, as AMD and TSMC have been unable to capitalize on the low end.

That said, it’s hard to be too cynical with AMD’s lone miss (the Radeon HD 77xx) — the chipmaker has delivered 3 new chips in 3 months, and more are on the way.  And it’s important not to underestimate the tremendous value add that these GPUs cores are to AMD’s accelerated processor units (APUs), chips that proved a smash sales success in 2011.

AMD may see even greater gains by incorporating GCN into its Trinity APU (middle) and future chips.  (The Radeon HD 79xx Tahiti chip is seen on the left.) [Image Source: Jason Mick/Global Tech News]
In that sense GCN cards may be exciting to enthusiasts.  But their greatest value may come when the architecture’s improvements are incorporated into APUs.  AMD’s the new Trinity APUs will incorporate pieces of GCN, and their next-generation 2013 successor, Kaveri will dive even deeper.  With our own polling showing strong interest in AMD’s promised sub-$500 ultrathin laptop solutions, Pitcairn‘s GCN “little brothers” inside APU dies may in time bring AMD far more revenue that it’s first 28 nm discrete graphics push, which is currently completing its rollout.