When we first heard about the overclocking potential of the 4890 from AMD, we were a bit skeptical. At the same time, the numbers we were hearing were impressive and AMD doesn't have a history of talking up that sort of thing to us. There have already been some investigations around the web that do point to the 4890 as having some healthy overclocking potential, so we decided to try our hand at it and see what we could come up with.

We are testing review samples, which means that our parts may have more overclockability than off the shelf cards, but we can't attest to that at this point. What we do want to explore are the overclocking characteristics of the 4890 and how different adjustments may or may not affect performance. From what we are seeing around the web, many people are getting fairly close to the speeds we tested. Every part is different, but while clock speeds may vary, the general performance you can expect at any given point will not.

So what's so special about this AMD part that we are singling it out for overclocking anaysis? Well, the GPU has been massaged to allow for more headroom, some of which hasn't been exploited at stock clock speeds. This is the first time in a long time (or is it ever?) we are seeing multiple manufacturers bring out overclocked parts based on an AMD GPU at launch. With this as the flagship AMD GPU, we also want to see what kind of potential it has to compete with NVIDIA's top of the line GPU.

But it's more than just the chip. We also are also interested in how well the resources on the board are balanced. Core voltages and clock speeds must be selected along with framebuffer size and memory clock. These considerations must account for a target power, heat, noise and price. For high end parts, we see the emphasis on performance over other factors, but there will still be hard limits to work within.

Because of all this, balancing hardware specifications is very important. Memory bandwidth needs to be paired well with core speed in order to maximize performance. It doesn't do us as much good to have an infinitely fast core if we have slow memory that limits performance. We also aren't well served by really ridiculously fast memory if the core can't consume data quick enough. Using resources appropriately is key. And AMD did a good job balancing resources with the 4890.

Rather than just test the semi-official overclock (which is just a 50MHz core clock boost to 900MHz), we decided to test multiple core and memory overclocks (and one core + memory overclock) to better understand the performance characteristics of this beast. As expected, overclocking both core and memory saw the best results followed by only overclocking the core. Just boosting memory speed on its own didn't seem to have a significant impact on performance despite the large overclock that was possible.

So why not sell every chip at the "overclocked" speed? Well, it's all about yield. Our guess is that while the change that AMD made were certainly good enough to boost clock speed over the 4870 by a healthy margin that there were a good number of parts that couldn't be pushed up to 900MHz and AMD really didn't want to sell them as cheaper hardware. We haven't heard that endorsing the idea overclocked parts is really a policy change for AMD, so it might just be that previous layout, routing, and design choices provided for a narrower range of overclockability around the target clock frequency.

What ever the reason for it, we now have overclockable hardware from AMD. Our analysis starts with an in depth look at percent increase in performance, but if all you care about is raw performance data, we've got plenty of that in the second half. And with it comes a surprise in our conclusion we never expected.

Cranking GDDR5 All the Way Up
POST A COMMENT

61 Comments

View All Comments

  • Sylvanas - Wednesday, April 29, 2009 - link

    This is exactly the kind of review I like to see, overclockability is a major factor for me in purchasing new hardware. Better than the 4890 launch article, good job. Reply
  • SiliconDoc - Saturday, June 06, 2009 - link

    Better remember this then:
    " We absolutely must caution our readers once again that these are not off-the-shelf retail parts. These are parts sent directly to us from manufacturers and could very likely have a higher overclocking potential than retail parts "
    Reply
  • Live - Wednesday, April 29, 2009 - link

    I really liked this article. Covered everything needed and was very informative. Reply
  • GeorgeH - Wednesday, April 29, 2009 - link

    Interesting read, but I was a bit disappointed not to see the 4850x2 included in the benchmarks. The 1GB model is currently at very rough price parity with the 4890 and the 2GB model still cheaper than a 285. As such, it would've been nice to be able to more easily note the advantages of a multiple GPU card over a single GPU card cranked up to ludicrous speed. Reply
  • Minion4Hire - Wednesday, April 29, 2009 - link

    The numbers used for the 4850 in this article correlate to those in the Multi-GPU article from February. So all you really need to do is compare the 4850 X2 results from that article to the 4890 results in this article. The two are closely matched, although I'd be willing to bet that the perceived performance and fps range is tighter and more consistent on the 4890 than the 4850 X2, as single GPU solutions usually are. Reply
  • Tuvok86 - Wednesday, April 29, 2009 - link

    You'd better undervolt rather than underclocking.
    My 4890 manages a good downvolt at stock speed, resulting in low temps
    Reply
  • kmmatney - Wednesday, April 29, 2009 - link

    That is a good point. I have setup a 2D profile in ATT which undervolts the card (you can undervolt, but not overvolt with ATT) and that does help in 2D. I haven't tried undervolting at stock speed (although mine's a OC version, so it may need the full voltage). Reply
  • kmmatney - Wednesday, April 29, 2009 - link

    I have an HD4890 and it does overclock well. But it's just too damn loud. I've been actually underclocking it for most of my games, as its fast enough to run them fine while underclocked, and it keeps the noise down. It's just not fun running it overclocked and having your game drowned out by a hairdryer. Headphones help. Reply
  • Veteran - Wednesday, April 29, 2009 - link

    The title is a little bit stupid if you ask me, a 4890 can go way further then 1GHz on the core and 1.2GHz for the RAM. Why didn't AT go further then normal achievable clocks? The title says to the max, too bad it cannot make up the promise.
    Interesting read though, must have cost a tremendous amount of work.
    Reply
  • DerekWilson - Wednesday, April 29, 2009 - link

    Well ... it is to the maximum value the built-in overclocking features of the driver will let you set the card. So that's where "to the max" came from.

    Yes with 3rd party tools you can get higher on some hardware, but we didn't want to go into aftermarket cooling and not everyone can even make it to 1GHz ... We wanted this based somewhere in achievability.

    And I'm glad it was interesting :-)
    Reply

Log in

Don't have an account? Sign up now