ATI Radeon HD 3870 X2 Review :: ATI 3870X2 Features

02-13-2008 · Category: Hardware - Video Cards

By Ben Sun
  • Shader Model 4.1
  • 128-bit HDR Lighting
  • 2x320 Unified Shaders
  • 55 nanometer process
  • 2x 666 million transistors 1332 million total
  • Core clock 825 MHz
  • Memory clock 1.8GHz effective
  • Memory interface 256-bitx2
  • Memory type GDDR3
  • Memory size 1024MB
  • Interface PCI Express 1.1
  • Up to 16x AA and 16x AF

ATI’s 3870X2 is literally two of their RV670 video cards on one PCB (Printed Circuit Board). The 3870 was launched in 2007 with the intent of taking on NVIDIA’s mainstream video card the 8800GT. The 3870 was the first video card in the world to support DirectX 10.1 features which I just covered in the previous page, and was the first card to fully support the new PCI Express 2.0 standard. ATI uses a PLX PCI Express bridge chip to bridge the two GPUs. The 3870x2 offers 16 lanes of PCI Express 1.1 to each RV670 chip and 16 lanes to the PCI Express slot, meaning that there are 48 PCI Express lanes total. The 3870 is the first card on the market to support Shader Model 4.1, the center point of the new DirectX 10.1 feature set.


ATI Radeon HD 3870 X2 Review AF

AF

ATI Radeon HD 3870 X2 Review AA

AA

ATI Radeon HD 3870 X2 Review Adaptive anti-aliasing

Adaptive anti-aliasing

ATI Radeon HD 3870 X2 Review Software

Software

ATI Radeon HD 3870 X2 Review Hardware

Hardware


The 3870x2 has 640 Unified Shaders, which is 2x320 found on a single 3870. There are 1332 million transistors on the card, 666 million on each 3870 chip which is 34 million less than the 2900XT, ATI’s last high-end card. ATI was the first video card company to introduce chips on the 55 nanometer process with the 3870. The die size of the 3870 is 199mm2 which is ½ that of the 2900XT. The smaller die size and process contribute to lower power consumption and ATI says that the peak power consumption is 200W or 15W less than a single 2900XT from their last generation. As we’ll see in the performance area, this means that they’ve nearly doubled the performance for the same power requirement.

The card has 1GB of GDDR3 memory arranged in 8 32MB memory chips per GPU on each side of the PCB for a total of 1GB (16x2x64). The original HD3870 had a memory clock frequency of 2.25GHz, not a bottleneck on the card. The memory bandwidth found on the 3870x2 is 57.6GB/second per chip, with 256-bit memoryx1.8GHz effective memory clock/8 bits per byte being the formula used to calculate the bandwidth. This brings a total of over 115.2GB/second of memory bandwidth to the card, split into 2x 57.6GB/second per GPU. The clock speed on the 3870X2 is an impressive 825MHz, or 50MHz faster than the 3870 single card.

One thing that the bridge chip adds support for on the 3870X2 is the ability to run the card on a non-Crossfire supporting motherboard. I was able to run the card on a 780i SLI board which is an NVIDIA SLI board without issue. The other issue with ATI cards in Multi-GPU format was the fact that the cards couldn’t do multi-monitor solutions. The 3870X2 allows Multi-Monitor on the two 22” LCDs we use in our testing lab. The 3870x2 card does Crossfire natively, meaning that the card does not require enabling or disabling Crossfire via the AMD Control Panel applet as it’s just naturally on by default.