HIS Radeon HD3870 Review & Crossfire Performance Preview

by Michael "SKYMTL" Hoenig     |     November 14, 2007

The New ATI Lineup…..blissfully simple

After going through a pair of reviews with the utterly confusing Nvidia naming process, ATI’s lineup seems extremely clear-cut and focused. AMD has chosen to use a very simple naming process for their new family of 3800-series of graphics cards: the xx70 designation is reserved for the higher-performing part while the xx50 is used for the intermediary part. Simple, no?

At the top of the spectrum we have the soon-to-be-discontinued HD2900XT with its 512-bit memory interface and power-hungry 80nm manufacturing process. At the lower end the HD2600-series stays with us for a little longer (as does the 2400-series) but both the XT and Pro versions get a pretty large price cut to an undetermined amount. According to AMD roadmaps, both the 2600 and 2400 series will be brought over into Q1 2008 and will not be replaced for at least the next few months.

Into this mix comes the aptly-named HD3870 card which is based on the new 55nm RV670XT core. This card does not represent a revolution in GPU design but it is rather the next step in the evolution of the ATI’s R600 architecture. That being said, the specifications do tend to look a lot like the outgoing and much-maligned HD2900XT cards. Fortunately for us, ATI and AMD have added so much more than a simple die-shrink; they have added PCI-E 2.0 compatibility, DX10.1 support, Unified Video Decoder compatibility and a host of other features. The DX10.1 feature is most definitely a stand-out since the HD3800-series will be the first graphics cards to support the new features which will be released with Windows Vista Service Pack 1. There have been a few leaks of DX10.1 “white papers”; one of which can be found here: http://www.pcper.com/images/reviews/...per%20v0.4.pdf

Personally, the one thing that interests me the most is the impact which the die-shrink will have on power consumption. The HD2900XT was a power hungry beast with its 80nm core and the 55nm core of the HD3870 will have a very positive impact on power consumption and heat production. There is an additional feature called Power Play which also impacts power consumption but we will look at that a bit later.

Overall, the specifications of the HD3870 give it quite a bit of credibility in today’s GPU market. The core is clocked at a whopping 777Mhz (interesting clock frequency, no?) while the GDDR4 memory is clocked at a face-slapping 2.25Ghz. Even with all that speed, you can still have a dud of a card if it is not equipped to handle high-texture scenarios which are found in many of today’s games. The HD3870 has very little to worry about on this account since it is equipped with 320 Stream Processors and 16 texture units. At this juncture I think it is important to call into account the difference between Nvidia’s Stream Processors and those on ATI GPUs. Instead of running the risk of sounding long-winded, I will direct you to this excellent article by Anandtech: AnandTech: ATI Radeon HD 2900 XT: Calling a Spade a Spade

While we are not reviewing the Radeon HD3850 in this article, we will touch on it nonetheless. This card is based on the 55nm RD670Pro graphics core and it is supposed to bridge the performance and price gap between the HD2870 and the HD2600XT. It is essentially and underclocked HD3870 with 256MB of GDDR3 memory instead of the 512MB of GDDR4 found on its larger sibling.

Power Play. No, not the hockey kind.

Now we come to one of the more interesting features behind these new cards from ATI: Power Play. Even though the 55nm-based core combined with GDDR4 memory should keep power consumption down, AMD has gone the extra step by giving these cards additional power management capabilities. The RV670 cards can now dynamically reduce their clock speeds and even voltage in order to increase efficiency by leaps and bounds over the older HD2900XT cards.

Imagine you have a HD2900XT or an 8800GTX and you want to work on a spreadsheet for work or an essay for one of your classes. I have done this before and no matter what, even in 2D clock modes the R600 and G80-based cards produce waves of heat from their heatsinks. There is nothing like working your butt off but you can’t concentrate because you are sweating like a pig because of the heat your graphics card produces. Well, with the HD3800-series you do not have to worry about this any longer since it drastically throttles back its voltages and speeds so heat and power consumption is no longer much of an issue when doing idle tasks.

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