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A Look At The Tech Specs

Benchmarking AMD's 768-Shader Pitcairn: Not For Public Consumption
By , Benjamin Kraft

We can’t help but wonder why AMD leaves such a large gap in its line-up instead of plugging it with a card that would practically be without a direct competitor. Even overclocking our Radeon HD 7770 to 1.15 GHz doesn't reliably push it to that half-way point between a stock 7770 and 7850. So, filling the void by simply increasing the clock speed of an existing product is not an option for AMD. How about tacking on a few more shader units to a Cape Verde GPU? That seems just as unlikely since it requires a redesign.

Now, we could speculate that the yields for AMD’s Pitcairn chips are apparently so good that there simply aren’t enough partially-defective chips to “harvest” and recycle into a card that slots in between the 7700 and 7800 families (a move we’ve seen from AMD and other companies in the past). AMD's Radeon HD 5830 and Nvidia's GeForce GTX 560 TI 448 Core are good examples.

On the other hand, it's just good business to address an audience looking for a better card at a certain price point, even if it means artificially paring down an otherwise healthy existing product. Again, that’s something we’ve seen in the past on a number of occasions.

Here’s how our engineering sample would fit into AMD’s existing portfolio of GCN-based cards:


Radeon HD 7770
Radeon HD 7850
768-Shader ES
Radeon HD 7850
Radeon HD 7870
Stream Processors
640
768
1024
1280
Texture Units
14
64
64
80
Full Color ROPs
16
32
32
32
GPU CLock
1000 MHz
860 MHz
860 MHz1000 MHz
Texture Fillrate
40 Gtex/s
41.3 Gtex/s
55 Gtex/s
80 Gtex/s
Memory Clock
1125 MHz
1200 MHz
1200 MHz
1200 MHz
Memory Interface
128-bit
256-bit
256-bit
256-bit
Memory Bandwidth
72 GB/s
153.6 GB/s153.6 GB/s
153.6 GB/s
Video-RAM
1 GB GDDR5
2 GB GDDR52 GB GDDR52 GB GDDR5
Transistors (Billion)
1.5
2.82.8
2.8
Manufacturing Process
28 nm
28 nm28 nm
28 nm
Aux Power
1 x 6-pin1 x 6-pin1 x 6-pin
2 x 6-pin
Power Consumption (max. measured)
80 W
120 Watt*
130 W175 W
Market Price
(Newegg, May 08, 2012)
~$149+
~$200+ (If we got our way)
~$250+
~$330+

*Note: This is an engineering sample, not a final GPU.

Actually, the tech specs represent a pretty plausible starting point for our analysis, since a 25 percent reduction in shader units should translate to between 20 and 25 percent less performance, depending on the workload. Since we’re dealing with an engineering sample on a prototype board intended to bring up full Radeon HD 7850 cards, attributes like power consumption and heat don't bear the weight they would if we were looking at a piece of production hardware. Let’s not forget, the express purpose of the card we have in-house is to give board partners a way to tweak and improve their designs, bringing down power consumption and optimizing cooling on final boards. With that said, we don’t think AMD has anything to worry about, based on the numbers we got from our engineering sample. For what it is, the board returned completely acceptable results.

Even in its prototype stage, our review sample does not disappoint. So, without further ado, let’s get cracking on those benchmarks!

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  • 0 Hide
    jakjawagon , 9 May 2012 02:01
    Why bother editing out the vendor? The previous story and some of the picture names on this article clearly show it's Afox.
  • 0 Hide
    LePhuronn , 12 May 2012 09:51
    7830 1GB all the way - I reckon price-conscious gamers would be ALL over it (and one would be going into my Sugo SG05 immediately)
  • 0 Hide
    asal1980 , 16 May 2012 15:29
    Instead of coming equipped with the usual 1024 shaders, our engineering sample sported only 768 active shader cores.