AMD Radeon HD 4870

Written by John Yan on 7/17/2008 for PC  

AMD’s recent video card activity has been getting them back into the game as their recent cards have shown they are taking steps in the right direction. Well, if the next two cards coming out are any indication, AMD is back in a big way and giving NVIDIA a big run for their money. AMD’s launching the ATI Radeon HD 4800 series of cards and we have a look at their two initial offerings in the ATI Radeon HD 4850 and the ATI Radeon HD 4870.

First let’s look at what makes the 4800 series tick. For starters the cards are built on a 55nm fabrication process. Until recently with NVIDIA’s 9800 GTX+ launch, the ATI Radeon HD 4800 series were the only video cards to do this. As you know, smaller die equals less power needed and heat generated as well as decreasing the cost of producing the cards. AMD is able launch these cards at a very affordable price partially due to this.

The GPU codenamed R770 has been in the works for over two and a half years. Efficiency was one of the key goals and the engineering team worked really hard to make sure this was achieved with the R770. Deficiencies in the R600 line were studied, redesigned, improved upon, and incorporated in the R770. 965 million transistors, 800 stream processors, 40 texture units, and 16 render back-ends are just some of the processing power the R770 features.

Memory comes in GDDR3 or GDDR5 flavors. Data rates on GDDR5 can be up to 5X that of GDDR3 and 4X that of GDDR4. GDDR5 isn’t just about speed as there are new error correction mechanisms to help increase accuracy in calculations. There aren’t any other video cards using GDDR5 out there currently so the 4870 series of cards is the first out of the gate with it onboard. The 4850s use the lower rated GDDR3 and it helps keep the costs of the video card lower using the lesser performing memory. While the new NVIDIA card is using a 512-bit memory bus, the 4800s use a 256-bit memory bus. What the 4870 lacks in width makes up for with speed though with the GDDR5 ram. The faster ram will help compete with the bandwidth of a 512-bit memory bus in the NVIDIA cards.

TeraScale is what they call their new graphics engine. The name comes from the fact that there’s at least a processing rate of one teraflop or more. Compared to the ATI Radeon HD 3870, that’s more than double what the previous generation’s card is capable of.

DirectX 10.1 is supported of courses so you’ll be ready for the latest games on a Vista operating system. As with previous cards, CrossfireX technology is also in play allowing for multiple cards to be linked together for improved performance. We’ll be looking at Crossfire performance in a future article but recent reports state that you can get performance close to or surpassing NVIDIA’s single configurations of the GeForce GTX 260 and GeForce GTX 280 at a lower price point. Up to four GPUs can be linked together if your motherboard and power supply supports it.To help improve the quality of graphics in games, offers the basic anti-aliasing modes as well as their Edge Detection technology as well. Various filters are used to help improve the image as the AMD hardware detects edges and applies them in those areas. Theoretically, you will get three times the sample rate with the advanced filtering methods. The AMD 4800 series increases the speed at which this can be achieved. In some cases, you can turn up to 8X AA with a minor performance hit over 4X AA.

Video support has always been a big part of the Radeon series of cards and the 4800 set is no exception. Unified Video Decoder 2 helps process video and alleviates the CPU from doing the work thereby offering smooth video playback. Codecs supported include VC-1, H.264, and MPEG-2. When converting video, you can get almost double the speed of real time for high definition video conversion. The HD 4800 series can upscale content past 1080p resolution so it can even enhance DVD picture quality on big displays. With onboard HDCP you’ll be able to view all your HDCP protected content on HDCP supported displays. The series also features an HDMI connection so you can pipe both video and audio through one connection on the video card.

So in a nutshell, we have a very feature rich set for the ATI Radeon HD 4800 line of cards. Below is a quick rundown of features for the cards
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ATI Radeon™ HD 4800 Series - GPU Specifications

• 956 million transistors on 55nm fabrication process
• PCI Express 2.0 x16 bus interface
• 256-bit GDDR3/4/5 memory interface
• Microsoft® DirectX® 10.1 support
  • Shader Model 4.1
  • 32-bit floating point texture filtering
  • Indexed cube map arrays
  • Independent blend modes per render target
  • Pixel coverage sample masking
  • Read/write multi-sample surfaces with shaders
  • Gather4 texture fetching
• Unified Superscalar Shader Architecture
  • 800 stream processing units
    • Dynamic load balancing and resource allocation for vertex, geometry, and pixel shaders
    • Common instruction set and texture unit access supported for all types of shaders
    • Dedicated branch execution units and texture address processors
  • 128-bit floating point precision for all operations
  • Command processor for reduced CPU overhead
  • Shader instruction and constant caches
  • Up to 160 texture fetches per clock cycle
  • Up to 128 textures per pixel
  • Fully associative multi-level texture cache design
  • DXTC and 3Dc+ texture compression
  • High resolution texture support (up to 8192 x 8192)
  • Fully associative texture Z/stencil cache designs
  • Double-sided hierarchical Z/stencil buffer
  • Early Z test, Re-Z, Z Range optimization, and Fast Z Clear
  • Lossless Z & stencil compression (up to 128:1)
  • Lossless color compression (up to 8:1)
  • Up to 8 render targets (MRTs) with anti-aliasing
  • Accelerated physics processing
• Dynamic Geometry Acceleration
  • High performance vertex cache
  • Programmable tessellation unit
  • Accelerated geometry shader path for geometry amplification
  • Memory read/write cache for improved stream output performance
• Anti-aliasing features
  • Multi-sample anti-aliasing (2, 4, or 8 samples per pixel)
  • Up to 24x Custom Filter Anti-Aliasing (CFAA) for improved quality
  • Adaptive super-sampling and multi-sampling
  • Gamma correct
  • Super AA (ATI CrossFireX™ configurations only)
  • All anti-aliasing features compatible with HDR rendering
• Texture filtering features
  • 2x/4x/8x/16x high quality adaptive anisotropic filtering modes (up to 128 taps per pixel)
  • 128-bit floating point HDR texture filtering
  • sRGB filtering (gamma/degamma)
  • Percentage Closer Filtering (PCF)
  • Depth & stencil texture (DST) format support
  • Shared exponent HDR (RGBE 9:9:9:5) texture format support
• OpenGL 2.0 support
• ATI Avivo™ HD Video and Display Platform
  • Unified Video Decoder 2 (UVD 2) for H.264/AVC, VC-1, and MPEG-2 video formats
    • High definition (HD) playback of Blu-ray and HD DVD video
    • Dual stream (HD+SD) playback support
    • DirectX Video Acceleration 1.0 & 2.0 support
    • Support for BD-Live certified applications
  • Hardware DivX and MPEG-1 video decode acceleration
  • Accelerated video transcoding & encoding for H.264 and MPEG-2 formats
  • ATI Avivo Video Post Processor
    • Color space conversion
    • Chroma subsampling format conversion
    • Horizontal and vertical scaling
    • Gamma correction
    • Advanced vector adaptive per-pixel de-interlacing
    • De-blocking and noise reduction filtering
    • Detail enhancement
    • Color vibrance and flesh tone correction
    • Inverse telecine (2:2 and 3:2 pull-down correction)
    • Bad edit correction
    • Enhanced DVD upscaling (SD to HD)
    • Automatic dynamic contrast adjustment
  • Two independent display controllers
    • Drive two displays simultaneously with independent resolutions, refresh rates, color controls and video overlays for each display
    • Full 30-bit display processing
    • Programmable piecewise linear gamma correction, color correction, and color space conversion
    • Spatial/temporal dithering provides 30-bit color quality on 24-bit and 18-bit displays
    • High quality pre- and post-scaling engines, with underscan support for all display outputs
    • Content-adaptive de-flicker filtering for interlaced displays
    • Fast, glitch-free mode switching
    • Hardware cursor
  • Two integrated dual-link DVI display outputs
    • Each supports 18-, 24-, and 30-bit digital displays at all resolutions up to 1920x1200 (single-link DVI) or 2560x1600 (dual-link DVI)
    • Each includes a dual-link HDCP encoder with on-chip key storage for high resolution playback of protected content³
  • Two integrated 400 MHz 30-bit RAMDACs
    • Each supports analog displays connected by VGA at all resolutions up to 2048x1536
  • DisplayPort output support
    • 24- and 30-bit displays at all resolutions up to 2560x1600
  • HDMI output support
    • All display resolutions up to 1920x1080
    • Integrated HD audio controller with support for stereo and multi-channel (up to 7.1) audio formats, including AC-3, AAC, DTS, DTS-HD & Dolby True-HD, enabling a plug-and-play audio solution over HDMI
  • Integrated AMD Xilleon™ HDTV encoder
    • Provides high quality analog TV output (component/S-video/composite)
    • Supports SDTV and HDTV resolutions
    • Underscan and overscan compensation
  • Seamless integration of pixel shaders with video in real time
  • VGA mode support on all display outputs
• ATI PowerPlay™ Technology
  • Advanced power management technology for optimal performance and power savings
  • Performance-on-Demand
    • Constantly monitors GPU activity, dynamically adjusting clocks and voltage based on user scenario
    • Clock and memory speed throttling
    • Voltage switching
    • Dynamic clock gating
    • Central thermal management – on-chip sensor monitors GPU temperature and triggers thermal actions as required
• ATI CrossFireX™ Multi-GPU Technology
  • Scale up rendering performance and image quality with two, three, or four GPUs
  • Integrated compositing engine
  • High performance dual channel bridge interconnect

The Radeon HD 4800 series looks to deliver performance in both games and video. AMD is looking to push multi-GPU setups rather than single high-end cards and having cards priced at a reasonable amount can help further this cause. I’ve been using NVIDIA cards in my main machines for the past few years so I’m anxious to see if the Radeon HD 4800 series can steer me back to the red side of things.The high end card for the 4800 series is the ATI Radeon HD 4870. The GPU’s core clock speed comes in at 750 MHz while the card contains 512MB of GDDR5 memory running at 900MHz. The brand that was sent to us to look at is from VisionTek and it looks to be a full retail version containing all the necessary connectors. While the 4850 has 1.0 TeraFLOPping power, the 4870 gets an extra 20% increase with 1.2 TeraFLOPS of goodness. The faster memory, increase in core clock speed, and other changes make this card retail for $299 which is a $100 premium over the 4850. AMD has positioned this card to compete with the GeForce 9800 GTX.



While the 4850 are single slot cards, the Radeon HD 4870 card is a dual slot solution with an oversized cooler. Those that have cards in slots adjacent to the PCI-E slot will need to keep that in mind. Two six-pin power connectors are needed to power the card. It’s slightly longer than a Radeon HD 4850 but not too much. Max power draw is rated at 160W.

The fan is quiet but the automatic settings AMD has it set at is pretty low. When you first turn on the computer, you are greeted with an incredibly loud whirl of the fan and it can be pretty surprising the first time you hear it. Even setting the fan to run at 65% capacity generated a pretty loud noise. Now most users probably won’t need to touch the settings but those that want to do some overclocking will want to push the fan speed be prepared to endure some pretty ear rattling noises.

Included with the card are a few connectors. For starters a DVI-HDMI dongle will let use one cable for both video and audio allowing for 7.1 surround sound to be passed to an audio source. Those stuck with VGA monitors can use the DVI-VGA convertor. Component cables will give you HD signals to a TV if you don’t have a DVI or HDMI connector on your display. The box also includes a flexible Crossfire connector to let you link up another card.The testing setup includes

• Intel E6400
• Biostar P45 Motherboard
• 2 GB PC-6400 DDR2 ram
• Windows Vista w/ Service Pack 1

For comparison, we’ll compare the AMD Radeon HD 4870 with a GeForce 8800GTX and an AMD Radeon HD 4850.

First up is the 3DMark Vantage from Futuremark.


Crysis is the current game that pushes video cards to their limit. The latest from Crytek, Crysis offers some of the most incredible visuals you see today on the PC. For the test we ran through a flyby around the island that lasted about 4 minutes and recorded the average frames per second. Resolution was set at 1600x1200.



Using the AMD Control Panel, I was able to overclock the clock speed from 750MHz to 780MHz and the memory from 900MHz to 1090MHz. I couldn’t get the core to overclock as much as I did with the Radeon HD 4850 but I was able to push the memory more than I did with the 4850. I had the fan running at 65% capacity when I did this and the noise generated by the fan was pretty loud. That said, here are the score comparisons below.


3D Mark Vantage saw a marked improvement of about 1000 in the GPU score while Call of Duty 4 saw a slight improvement with the new speeds.

So how does the card compare to a Radeon HD 4850 when clocked at similar speeds? For that I underclocked the Radeon HD 4870 to Radeon HD 4850 speeds in both clock and memory. Memory was off by 10MHz though just to clarify. In any case, let’s see how much of an improvement you’d get with just the different memory onboard.


In both games, the Radeon HD 4870 offers a slight performance gain over the Radeon HD 4850. While 3D Mark Vantage had a bigger delta, performance in games tell you that the DDR5 memory does do a little to help when clocked at the same speeds of a DDR3 card.

The Radeon HD 4870 will run you $299 and it’s still a pretty good deal. It was a better deal before NVIDIA dropped the price of their high end Geforce 260 and Geforce 280 cards but still a great buy nonetheless. It’s not the best bang for your buck as that award goes to the Radeon HD 4850 but AMD has done a great job at putting out a card at the higher spectrum of the midrange area. I’m anxious to see two of the GPUs on one card so we can get Crossfire performance without having to lose a PCI-E slot or more since the Radeon HD 4870 is a two slot card. While not as good of a deal as the 4850, the Radeon HD 4870 is still a great buy if you are considering on upgrading your current rig.