The Radeon 4890
|Radeon 4870/4890 Comparison|
|Radeon 4870||Radeon 4890|
|# of Transistors||956 Million||959 Million|
|# of Stream Processors||800||800|
|Compute Performance||1.2 TeraFLOPS||1.36 TeraFLOPS|
|# of Texture Units||40||40|
|Texture fillrate||30 GigaTexels/sec||34 GigaTexels/sec|
|# of ROPs||16||16|
|Pixel Fillrate||12 Gigapixels/sec||13.6 Gigapixels/sec|
|Z Fillrate||48 GigaSamples/sec||54.4 GigaSamples/sec|
|Memory Clock Speed||900MHz||975MHz|
|Memory Data Rate||3.6 Gigabits/sec||3.9 Gigabits/sec|
|Memory Bus Width||256-bit||256-bit|
|Memory Bandwidth||115 Gigabytes/sec||124.8 Gigabytes/sec|
|Max Board Power||160W||190W|
|Idle Board Power||90W||60W|
Based on ATI’s RV790XT GPU, the Radeon 4890 is fundamentally very similar to the RV770 architecture launched last year with the Radeon 4850/4870. The chip boasts the same 800-shader architecture as RV770, with the same basic configuration as ATI’s previous offering: you’ll see that all the fundamental pieces of the chip (number of texture units, ROPs, memory interface, etc) carry over unchanged. The biggest difference between RV770 and RV790 lies in clock speeds: the Radeon 4890 is clocked 100MHz higher on the GPU than the 4870. Because they’re so similar, the Radeon 4870 and 4890 can be combined together for mix-and-match CrossFire, just like the 4850 and 4870.
ATI says they’ve completely reworked the ASIC to enable higher frequencies; some 3 million transistors have been added to RV790, and the chip boasts a slightly larger die than its predecessor. So where did the new transistors go? With RV790, ATI has added decoupling capacitors in order to reduce the signal noise you’ll inevitably encounter as you begin to crank up the clock speeds. A decap ring completely encircles the ASIC. ATI also says they’ve retimed the entire chip to run at the higher frequencies. Power delivery has also been tweaked to the point where RV790 actually consumes slightly less power than RV770 at idle.
RV770 (top), RV790 (bottom)
Looking at the design of the RV790 reference board itself, we can see that ATI has made a few tweaks to enable higher clocks. With the board’s higher clock speeds comes higher power draw at load, in order to address this ATI adds more powerful capacitors to RV790. It also looks like additional power phases have been added to enhance power delivery.
On the cooling front, at first glance it looks like ATI has adopted the same cooler first introduced on the Radeon 4870. Considering how hot the Radeon 4870’s stock cooler is known for running, in addition to the higher temps that are inevitable as you crank up the clock speeds, sounds like a recipe for disaster doesn’t it?
Fortunately this isn’t the case, if you look a little closer you’ll actually see that while the same all-copper heatsink/fan unit is carried over from the Radeon 4870, a third
copper heatpipe has been added to the mix for the 4890; previously the Radeon 4870 relied on just two heatpipes to draw heat off the GPU. With the addition of a third heatpipe, the Radeon 4890 actually runs cooler than the 4870, despite its higher clock speeds.
Finally, ATI outfits the Radeon 4890 reference board with 4.0Gbps GDDR5 memory modules from Qimonda.
Retail Radeon 4890 cards
In addition to the ATI reference board, so far we’ve managed to get our hands on cards from Sapphire and ASUS. Both of these cards are identical to the ATI reference design from a hardware perspective, with both companies electing to use the reference board design and clock speeds, although we’ve been told that both companies plan on offering more exotic Radeon 4890 cards with higher clocks in the near future.
Sapphire has two SKUs planned for the 4890 launch, the Sapphire Radeon 4890, and the Sapphire Radeon 4890 OC. The 4890 is the card we received today and operates at the stock ATI specifications, while the OC board is clocked at 900MHz core/1.0GHz memory, an improvement of 50MHz on the graphics core and 25MHz on the memory over the stock ATI 4890 speeds.
We have no doubt that Sapphire will eventually cook up even more exotic Radeon 4890 cards with special cooling. In the past the company has offered liquid-cooled cards, and we’re huge fans of their vapor chamber cooling technology found in their Vapor-X and Toxic cards.
Meanwhile, ASUS plans to differentiate themselves from other ATI board partners with their software. ASUS ships their Radeon 4890 boards with their Smart Doctor utility.
What’s special about Smart Doctor is that it provides the ability to not only OC the graphics core and memory, but you can also adjust these parameters based on usage. Three modes are provided: 3D (Smart Doctor automatically OC’s the card to the highest clocks when you boot up a 3D app), CPU (Smart Doctor will dynamically adjust clocks based on CPU usage), and by temperature (much like Overdrive used to do, Smart Doctor adjusts clocks based on the GPU’s current temp with four levels of OC’ing provided based on how cool the GPU runs).
Another neat feature that Smart Doctor provides is fan control. Like ATI’s Overdrive utility, you can manually adjust the fan’s RPMs with a simple slider, or you can go much further than that, with Smart Doctor’s Smart Cooling feature, you can define how fast the fan will spin at four different temperature boundaries. The temp boundaries can be as high or low as you’d like, with five different predefined fan speed settings to choose from: slow, medium, fast, and fastest, with fastest being 100% RPMs.
The ASUS box even mentions the ability to adjust GPU and memory voltages, although this feature unfortunately wasn’t working yet in our build of Smart Doctor, so we didn’t get a chance to test it. As anyone who has OC’ed a CPU can tell you, the ability to adjust voltage is crucial to getting the max OC out of your processor when overclocking. Once ASUS provides this functionality into Smart Doctor, you should theoretically be able to hit even higher clock speeds when OC’ing than you’d be able to reach with the standard GPU and memory voltage.
Smart Doctor also provides full hardware monitoring functionality, with the ability to set alarms if certain thresholds are hit.
In terms of price and availability, ATI has told us that Radeon 4890 cards will sell for as low as $229 after mail-in rebate. Cards will be made available starting today from ATI’s board partners, with two SKUs generally offered at launch: the stock offering with an 850MHz clock speed, and an OC SKU with clock speeds starting at 900MHz core and going up from there.
ATI says they’re binning RV790 GPUs, with the best chips going into the OC SKUs. Besides the 900MHz baseline, ATI hasn’t set any hard guidelines for their board partners when it comes to the OC SKU, so conceivably you could see some board partners go to 950MHz or even 1.0GHz if they’d like. It’s all up to them.
When it comes to OC’ing, thanks to the improvements ATI has incorporated into RV790, hitting 1.0GHz isn’t a pipe dream either. It’s a very real possibility with some chips. We’ve tested five different Radeon 4890’s so far, and managed to get one of them up to the 1.0GHz ceiling currently imposed by Overdrive. Two others hit speeds of 975MHz and 980MHz. Boards four and five hit GPU speeds of 940 and 960MHz. (All of them managed to hit memory speeds of 1.1GHz or more.)
These are much better OC’ing results than the 4870 could ever achieve.
As far as ATI is concerned, a Radeon 4890 X2 could be produced at some point if the demand is there. Right now they’re unsure if system vendors would be willing to put up with a card that draws up to 300W of juice; they’re polling them now to see where the interest level is. Obviously if the system builders won’t get onboard, the chances of a Radeon 4890 X2 ever seeing the light of day dwindle significantly, as it doesn’t appear ATI would do this without them considering where the economy is right now.
Cross your fingers enthusiasts…