Review: Just short of 1000MHz
The new addition to the Radeon family is called HD 4890 and it is AMD’s fastest single-GPU card at the moment. This card will let AMD catch up with the Geforce GTX 260 SP216, and it scores up to 10% better results than the HD 4870 1GB. Since these two cards are not any different specification-wise, the improved scores are a direct result of HD 4890’s higher clocks. It runs at 850MHz, which is 100MHz more compared to HD 4870’s 750MHz. GDDR5 got a boost as well and instead of 3600MHz now runs at 3900MHz.
The new card’s GPU is codenamed RV790 and it packs 959 million transistors. These two graphics cards, the HD 4870 and HD 4850 use the RV770 GPU, and it’s only the clocks that set them apart. We’re currently unaware of anything that’s changed for the RV790 besides optimization and increased clock speeds. There are still 800 stream processors in 10 SIMD clusters, and the 40 texture units and 16 ROPs have been left unchanged as well.
The card’s PCB however, went through some design changes, mostly to regulate additional power requirements, as HD 4890’s higher clocks require more juice to run.
Just like the RV770, the RV790 GPU is built in 55nm and offers 2.5 times more stream processors and texture units than the previous, HD 3800 generation. Additionally, you might remember that the HD 3800 generation lacked in antialiasing performance, and RV770 managed to fix that. With its higher clocks, HD 4890 has a processing power of 1360 GigaFLOPS, whereas the HD 4870 had 1200 GigaFLOPS.
The new card comes with surprising overclocking capabilities, enabling AMD to push the reference clock threshold to 850MHz, so we’re already hearing about partner card designs running at 900MHz. The story about good overclocking is true indeed, as GPU clocks can easily be pushed over 950MHz (1000+ MHz in certain cases), and the memory to over 1100MHz (4400MHz effectively). Overclocking Radeon HD 4870 cards was usually limited to the GPU 850MHz mark, which to HD 4890 is nothing but mere reference clocks, and it proves that AMD did a good job in optimizing the core. Although AMD touts the 1000+MHz core capabilities, we still advise you to be careful as overclocking of course isn’t covered by the warranty.
Note that Radeon HD 4890 starts at €215.
We’ll be seeing reference HD 4890 cards with 1GB of GDDR5 memory at 975MHz (3900MHz effectively), but many partners will opt on either 2GB or 512MB of memory on their cards. Sapphire announced Toxic HD 4890 with Vapor-X technology, and we’ll soon see some water cooled cards which will utilize the RV790’s overclocking potential to the max.
The memory interface is still 256-bit, but thanks to high GDDR5 clocks it has a bandwidth of 124.8GB/s.
Note that GDDR5 memory offers double the bandwidth of identically clocked GDDR3 memory. This means that 512-bit GDDR3 offers the same bandwidth as the 256-bit GDDR5, provided they run at same speeds.
Compared to the GTX 260, where 448-bit GDDR3 memory runs at 999MHz and offers a bandwidth of 111.9GB/s, the HD 4870 with its 256-bit GDDR5 memory clocked at 900MHz offering a 115GB/s bandwidth whereas the HD 4890 clocked at 975MHz scores a bandwidth of 124.8GB/s. Such high bandwidth is of course a direct result of the GDDR5’s speed, which on the HD 4890 runs at 3900MHz.
The cooler looks the same like on the HD 4870 card, but the area underneath the hood went through some design changes. The cooler design stayed the same, but it uses more copper than before, resulting in temperatures lower than on the HD 4870. Now we have three copper heatpipes going from the copper base to the heatsink whereas the HD 4870 uses two copper heatpipes.
Still, the “new” cooler is not significantly heavier as it uses one 8mm and two 6mm pipes, whereas the HD 4870’s cooling uses two thicker, 8mm pipes. Dissipation surface is still the same.
The fan is still the same, NTK Technologies’ CF1275-B30H-C004 DC12V 1.0A, and you can see it on the picture below.
The card is quiet in 2D mode, and while you can hear it in 3D mode, the sound is still not uncomfortably loud and your gaming audio will easily mask it. On the other hand, overclocking to more than 960MHz requires the fan to run at maximum rpm, which has proven to be too loud and your ears definitely won’t like that.
Only a careful observer will notice the difference between the HD 4870 and HD 4890, as an inexperienced eye will surely miss the differences on the back of the card.
The first picture shows the HD 4890 followed by the HD 4870. Notice the part around the green sticker, where the changes are most evident.
The power components have either been altered or replaced with new ones, and this card proudly boasts lower 2D consumption than its predecessor the HD 4870.
HD 4890’s maximum consumption is 190W, whereas the HD 4870 consumes 160W. Both cards require two 6-pin power cables. AMD still keeps the memory frequency at a maximum in 2D mode, which negaitvely impacts power consumption.
The good thing about the cooling is that it pushes the air outside of the case, thus surely making life easier for the rest of the in-case components. The fan is located towards the end and blows air trough the aluminum heatsink and towards the air outlets on the I/O panel.
RV790 offers 7.1 audio as well, courtesy of Realtek HD Audio processor which is integrated directly into the GPU silicone. There’s no need for additional cables, unlike Nvidia’s offerings where you’ll be using a SPDIF cable to bring the audio to the card if you want to send both video and audio to your HDTV device via one cable. This card provides HDMI via the provided DVI-to-HDMI dongle and the I/O panel features two dual-link DVI outs as well as S-Video out. UVD 2 video decoding engine will also provide benefits such as options dual-stream decoding and dynamic contrast enhancement.