Review: A great reference card
We've shown you what the Radeon HD 4850 is capable of a couple of times so far, and its price/performance ratio assured its popularity just days after the launch. This card features a crippled version of the RV770 chip, the full version of which can be found on HD 4870 cards priced at €200. Apart from the clocks and the memory type, the Radeon HD 4850 features everything that the more potent HD 4870 has to offer: 800 shaders, 40 texture and 16 ROP units, as well as DX 10.1 support.
MSI was kind enough to provide us with their reference HD 4850 featuring a single slot cooler, but before we move on to the results - let’s review the most important characteristics of the new HD 4800 generation.
You can see MSI R4850 in the picture below, and the only difference we’ve noticed in comparison to the reference card is a different sticker on the cooler. We still require one 6-pin PCI Express power connector and a single-slot cooler will keep the temperatures below 86 degrees Celsius.
ATI's RV770 core packs an impressive number of 965 million transistors and we already said that both HD 4870 and HD 4850 cards feature the same GPU at different clocks. While the older HD 4870 ran at 750MHz, Radeon HD 4850 runs at 625MHz (MSI’s R4850 also runs at these speeds). As far as memory is concerned, HD 4800 has a 256-bit memory bus, but in order to stay in the big league and fight with Nvidia’s latest offerings, ATI opted for GDDR5 memory. That way ATI managed to catch up with GTX 260 without expanding the memory interface. MSI's R4850 has 512MB of GDDR3 memory running at 1986MHz and features a bandwidth of 63.6GB/s.
The new GPU is built in 55nm process and brings 800 shader processors on both Radeon HD 4800 cards. Compared to the previous generation HD 3800 it’s 2.5x more shader processors and the same goes for 40 texture units (HD 3800 features 16). This is an important step forward because texture processor performance will no longer be a bottleneck. So far, we’ve had 16 texture processors grouped in 4 blocks, where each block had one filter unit at its disposal. RV770 features 40 texture processors grouped in 10 blocks, and each block has 4 filters at its disposal. Raster processors also went through a makeover. Just like RV670, RV770 has 16 ROP units but they are twice more effective in processing Z-buffers. RV770 can process 64 Z-values per clock cycle, and full screen antialiasing performance also improved.
Thanks to architecture optimization, ATI managed to build a card that’s not much bigger than the HD 3850 but it’s definitely more efficient. Although it doesn’t look powerful, this baby-beast is more than capable of taking on Nvidia’s 9800 GTX. The picture above shows two HD 4850 reference cards with a single-slot cooler, good enough to cool the GPU at reference speeds, but not for more serious overclocking.
MSI provides D.O.T. tool integrated into Catalyst drivers located on the driver CD. This overclocking tool will enable inexperienced users to increase the card’s efficiency by setting the core and memory clocks to predefined values. We got as high as 700MHz for the GPU and 1112MHz (2224MHz effectively) for the memory.
The card’s heatsink is made of an aluminum and copper combination, where copper is used for the cooler’s base. Its aluminum heatsink is quite large (almost identical to the one found on HD 3850 cards), but we’re quite sure that an even larger heatsink would come in handy in dissipating 110W off the GPU. The card is powered through a 6-pin PCI Express power connector, unlike HD 4870 which requires two. The following picture clearly shows the size difference between HD 4870 and HD 4850.
We’ve talked briefly about MSI’s HD 4870 here, and we’ll repeat that it’s an overclocked card running at 800MHz, compared to reference 750MHz for the GPU. The HD 4000 series features a new UVD (Unified Video Decoder) 2.0 Engine that enables dual-stream decoding and 7.1 channel (lossless) sound. Both dual-link DVI outs (supporting display resolution of up to 2560x1600) are HDCP enabled, whereas to get HDMI with sound you’ll have to use DVI-to-HDMI dongle provided by MSI.
The card’s left side is mostly uncluttered, from the memory all the way to the two dual-link DVI ports and standard mini-DIN port. The upper corner features a pair of CrossFireX connectors. Of course, CrossFire/CrossFireX is supported, so if your motherboard supports this technology you can chain up to 4 cards in CrossFireX.
The card comes in MSI’s standard packaging and within the box you’ll find a nicely wrapped HD 4850 (R4850) graphics card and a bundled copy of Colin McRae's “Dirt.”