ATI Radeon HD 3870 and 3850: 55nm RV670
The actual RV670-based Radeon HD 3870 and 3850 cards feature new PCB and heatsink cooler designs that are welcome changes from the Radeon 2900 XT.
The Radeon HD 3870 and 3850 are both about a half an inch shorter than the Radeon HD 2900 XT, and should have no clearance issues in any standard case. The Radeon HD 3870 pictured here features 512MB of GDDR4 memory clocked at 1126MHz (2.25GHz DDR), which results in just over 72GB/s of peak bandwidth. The card’s GPU is clocked at 777MHz – 37MHz higher than reference 2900 XT cards.
The Radeon HD 3870’s cooler is a dual-slot design, which thankfully is much quieter than the 2900 XT’s as well. We should note that when first powered on, the fan on the Radeon HD 3870 spins up and produces an significant amount of noise, but it quickly spins down and is near silent. Over the course of testing, it never spun up to top speed – even with two cards installed into a basic mid-tower chassis. We’re also told that some AIB partners are planning to produce single-slot versions of the HD 3870, but we have yet to see one for ourselves.
As you probably expected, the Radeon HD 3850 is based on the same PCB as the 3870, but it has lower GPU and memory clock speeds. The Radeon HD 3850 features a 670MHz GPU and 256MB of 830MHz (1.66GHz DDR) GDDR3 memory for a total of 52GB/s of peak bandwidth. Unlike the HD 3870, however, all reference-clocked HD 3850 cards feature a quiet single-slot cooler.
Something you may have also noticed is that both the Radeon HD 3870 and HD 3850 require only a single 6-pin supplemental PCI Express power connection. Thanks to the RV670’s 55nm manufacturing process and architectural tweaks, cards based on the GPU require much less power than the R600 and can get by with only a single additional power connection. Does that GPU look tiny by today's standards, or what?