Diamond Viper Radeon HD 3870 Showcase
Overclocking Results
ATI's reference specs call for 777 MHz for the GPU and 1126 MHz for the memory, and that's exactly what the Viper Radeon HD 3870 512MB is running at. The 1GB model, however, not only has that extra 512MB of memory added to it, but its core is running at a sweet 830MHz, with the GDDR3 memory at 870MHz. Great overclock already on the GPU, but we would like to tweak things even further.
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We found that the range offered to us using the Overdrive section of the Catalyst drivers was quite stifling when running the 1GB version: only a mere 830-850MHz was listed for the GPU. Instead, we decided to install ATI Tray Tools and plug in some numbers ourselves. It turns out that Overdrive might not have been too far off as the best stable speed we could run at was 850MHz for the core, and 968 MHz for the memory. With the 512MB version, we weren't able to reach as high, but we still added 50MHz on the GPU, settling in at 827MHz. Memory speeds also saw a similar boost, ending up at 1170 MHz.
Diamond Viper HD 3870 512 MB Overclock - GPU=827 MHz, Memory=1170 MHz
Diamond Viper HD 3870 1 GB Overclock - GPU=850 MHz, Memory=968 MHz
Diamond Viper HD 3870 512 MB Overclock - GPU=827 MHz, Memory=1170 MHz
Diamond Viper HD 3870 1 GB Overclock - GPU=850 MHz, Memory=968 MHz
While both cards got a little boost by the GPU and memory speed tweaking, we found that the 512 MB version profited the most. Trailing the 1 GB model in both original runs through Quake Wars and Half-Life 2, the larger compartive increase in GPU speed coupled with the much faster operation of the GDDR4 put the Radeon HD 3870 512 ahead by one to three frames per second when overclocked.
