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AMD A8-3850 APU Review: Llano Hits the Desktop

Author: MAC
Date: June 29, 2011
Product Name: AMD A8-3850
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An In-Depth Look at the HD 6000 Series IGPs



Llano is unique in the graphics department due to its use of the first ever integrated DX11 processing unit. Both Sandy Bridge and AMD’s last generation –the HD 4000-series which graced the Leo and Dorado platforms- IGPs were nothing more than warmed over DX10 parts. Intel’s own HD 3000 and HD 2000 Platform Graphics Controller was certainly a step in the right direction since it included support for DX10.1, Blu Ray 3D and a host of other features which brought it up to roughly the same level as an AMD HD 5450 DDR3. Unfortunately for Intel, the unit within the A8 series of APUs is an order of magnitude more powerful than anything previously installed as an integrated graphics processor.


At the heart of higher end Llano APUs beats an updated Redwood core which is code named Sumo. Many will remember the Redwood architecture from the popular HD 5600 series of discrete GPUs. While Sumo retains its Terrascale 2 DX11 architecture and VLIW5 design, a few improvements have been made along the way in order to bring this design up to modern standards.

One of the largest differences between Redwood and Sumo is the latter’s fabrication on Global Foundries’ new 32nm HKMG manufacturing process. This effectively cuts down on the physical die size while decreasing power consumption and thermal leakage and has effectively allowed AMD to cram more transistors into a limited on-die area.

Since AMD has done away with their 2-chip motherboard solution in favor of integrated Northbridge functionality onto the APU die, some changes to Redwood’s communication structure were necessary. The GPU core now interfaces with the built-in Northbridge via the 29.8 GB/s (and aptly named) Radeon Memory Bus to ensure latency is reduced to an absolute minimum.


The Sumo architecture adds two additional features which were lacking from the older AMD GPU designs: UVD3 and dynamic power gating. UVD3 brings increased HD output capabilities (which are detailed on an upcoming page) while dynamic power gating allows the GPU to shift though different power modes on the fly.

The primary use for power gating is to increase the battery longevity in the Sabine platform notebooks but it also has its uses in the desktop space. In order heighten overall efficiency, the graphics core will downclock to extremely low levels when an idle state is detected and increases clocks in proportion to the needs of the program being run.


The HD6550D graphics processor on the A8-series of APUs boasts 400 of the recently renamed “Radeon Cores” along with 20 texture units and 32 ROPs which basically makes it a Redwood XT core. Meanwhile, the slightly lower spec’d HD 6530D in the A6 APUs uses a design that’s similar to the Redwood LE but as with the HD 6550D, it uses slightly lower clock speeds in order to keep thermal output within reasonable limits. The HD 5670 / HD 6570 and HD 5550 are the discrete card analogs for these two cores and that’s actually quite impressive when you consider the perfectly respectable gaming performance each delivers.


The BIOS on any A75 or A55 board allows you to set aside a portion of the system memory to be used explicitly as the graphics core’s framebuffer. Anything from 32MB to 2GB can be selected in most motherboard BIOSes.

Using onboard memory as a means to interact with the graphics core means that both the system memory and the portion set aside for the GPU will be running at the same speeds. Therefore, AMD recommends that higher speed DDR3 is used. We’ll be testing the effect of memory bandwidth and capacity on in-game performance a bit later in this article.


While the power of AMD’s new class of onboard graphics controllers should be apparent by now, there are several periphery benefits as well. With UVD3’s proper support of stereo 3D content at a possible 120Hz, these APUs are better prepared for upcoming display technologies. As we can see above, anisotropic filtering is also a clear win for AMD but hopefully these impressive hardware specifications and a feature rich architecture translate into useful real world performance gains.
 
 
 

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