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ATI Radeon HD 3850 Graphics Card

PCB Design and Technical Characteristics

The PCB of the less expensive and less advanced RV670-based graphics cards is 1.5-2 millimeters longer than the PCB of the faster model. Its overall component layout resembles the ATI Radeon HD 3870, but there are a few differences:

 

For some reason the developer used a different component layout for the power circuit of the junior model. This cannot be explained by the lower power consumption of the Radeon HD 3850 as it uses the same two-phase circuit with four power transistors Infineon BSC 042N03LS in each phase and with an uP6201AQ chip as the controller. The uP6101BSA chip is responsible for memory. It’s clear the power circuit of the ATI Radeon HD 3850 can yield as much power as the one of the senior model although its load can hardly be more than 60 watts. Anyway, the card carries an external 6-pin PCI Express 1.0 connector, too. The other differences in the PCB wiring are due to the use of a different memory type: GDDR3 instead of GDDR4.

The reference sample of Radeon HD 3850 carries eight memory chips (Samsung K4J55323QI-BJ11, 256Mb, 8Mbx32, 1.9V). These chips are rated for a frequency of 900 (1800) MHz but they are clocked by the card at 830 (1660) MHz. There is some room for overclocking, but you can hardly achieve a frequency of 1000 (2000) with regular overclocking methods. Each chip has a capacity of 256Mb and a 32-bit bus, so the Radeon HD 3850 has a total of 256MB of memory accessed across a 256-bit bus. The memory bandwidth at the reference frequency is 53.1GB/s, which is lower than that of the senior model but higher than that of the GeForce 8800 GT 256MB. This should be quite enough considering that the Radeon HD 3850 is obviously not meant for high display resolutions.

The marking of the graphics core is just as vague as that of the Radeon HD 3870 core. We could only learn the manufacturing date from it: it is the 43rd week of 2007 (October 21-27), Taiwan. All the subunits of the GPU of the Radeon HD 3850 card are clocked at 670MHz. Die packaging has no protective frame.

There are no differences in the GPU configuration between the Radeon HD 3870 and HD 3850 except for memory controller settings for the use of GDDR4 and GDDR3 chips, respectively. The core incorporates 320 active ALUs grouped into 64 superscalar execution blocks with 5 ALUs and one branch unit in each. It also contains four texture processors equivalent to 16 TMUs, 4 rasterization processors (ATI calls them render back-ends) roughly equivalent to 16 ROPs, and a Compositing Engine for hardware CrossFire. Like the senior model, the ATI Radeon HD 3850 has two CrossFire connectors and can be used in a multi-GPU subsystem consisting of four such cards.

The card offers a standard selection of connectors: two dual-link DVI-I ports with support for DHCP and a display resolution of 2560x1600 pixels, and a universal 7-pin mini-DIN port responsible for analog video output in S-Video, Composite or YPbPr format. The card lacks VIVO functionality, like the Radeon HD 3870, offering no place for an appropriate chip. The more required feature for today is Audio-over-HDMI and it is supported fully by means of a DVI-I → HDMI adapter. Combining the best video-processor UVD, Audio-over-HDMI, the single-slot cooler form-factor and low power consumption, the ATI Radeon HD 3850 is perhaps the best graphics card for a modern multimedia system for processing HD content in VC-1 and H.264 formats.

 
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