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The Radeon HD 5830 Architecture

ATI Radeon HD 5830: Bridging The 5700- And 5800- Price Gap
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There are a lot of graphics cards from AMD in and surrounding the new Radeon HD 5830's price point, so let's have a look at the relevant players:


Radeon HD 5850
Radeon HD 5830
Radeon HD 5770
Radeon HD 4890
Shader Processors:
1,440
1,120
800
800
Texture Units:
72
56
40
40
Color ROPs:
32
16
16
16
Core Clock:
725 MHz
800 MHz
850 MHz
855 MHz
GDDR5 Memory Clock:
1,000 MHz
1,000 MHz
1,200 MHz
975 MHz
Memory Bus:
256-bit
256-bit
128-bit
256-bit
Memory Bandwidth (GB/s):
128
128
76.8
124.8
Compute Power (TFLOPs):
2.09
1.79
1.36
1.6
Transistors (billion):
2.15
2.15
1.04
0.959
Maximum Power:
151W
175W
108W
190W
Idle Power:
27W
25W
18W
60W


There's so much information to process here. At first glance, the new Radeon HD 5830 seems to completely outclass the Radeon HD 5770 with far higher memory bandwidth and almost a third more shader cores. Indeed, the new card looks comparable to the powerful Radeon HD 5850. Yes, there's a 22% reduction in shader cores, but there's also a 10% increase in GPU core clock speed to help offset the deficit.

Things look exceptionally positive for the new Radeon HD 5830 until you notice its Achilles heel: a lack of ROPs compared to the Radeon HD 5850. And we thought we were so very close to having Radeon HD 5850-class performance at $240! Of course, this is precisely the reason AMD cut the number of render back-ends in half compared to the Radeon HD 5870 and 5850. To put things in perspective, the Radeon HD 5830 might be able to execute shader operations almost as fast as the 5850, but its ability to render pixels to the screen has been crippled to the same specification as the Radeon HD 5770. We can expect the new Radeon HD 5830 to perform between the Radeons HD 5770 and 5850, but probably closer to the 5770 or Radeon HD 4890.

Speaking of the 4890, the Radeon HD 5830 looks to outclass it on all fronts, except the ROP count. Remember though, the Radeon HD 4000-series have been repeatedly proven to demonstrate a sizable shader-versus-shader performance advantage over the Radeon HD 5000-series when it comes to raw game performance. As a result, we'd expect the new card to demonstrate performance comparable to the Radeon HD 4890.

A Familiar Graphics Processor

The Radeon HD 5830 does not sport a new GPU, it simply employs the Radeon HD 5870 "Cypress" processor, crippled to the new specification and dubbed Cypress LE. In fact, AMD's power usage specifications suggest that the Radeon HD 5830 will be based on the high-end Radeon HD 5870 card instead of the smaller 5850. And our reference card was built on a full-sized Radeon HD 5870 PCB, though we'll go into that in more depth on the next page. For now, here is a Radeon HD 5870 block diagram that shows how much of the GPU has been disabled.

We've been through the Radeon HD 5000-series architecture in detail in our Radeon HD 5870 launch article so I won't rehash the minutia. We will look at the differences in the new Radeon HD 5830 though: as you can see, the new Radeon HD 5830 has 13 SIMD engines, compared to the 5870's 20, but only half of the render back-ends. We can definitely see where the performance bottleneck will lie. Each of the 14 SIMD engines hosts four texture units and 16 stream processors, and each stream processor with five ALUs (AMD calls these stream cores). As a result, this GPU boasts 1,120 stream cores and 56 texture units.

Note that the GPU retains its four 64-bit memory controllers, even though the number of render back-ends has been halved from four to two. Each render back-end contains eight color ROP units, resulting in a total of 16 ROPs and a 256-bit memory interface.

As with the rest of the Radeon HD 5000 family, AMD dedicated a lot of its transistor budget to features like DirectX 11 and Eyefinity. Of course, all of these features carry over to the Radeon HD 5830. With the aforementioned launches this month, we've covered them ad infinitum, so to read more about these features please check the other Radeon HD 5000-series stories linked to at the end of this piece.

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