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
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  • gold333 - Monday, May 04, 2009 - link

    Guru3d has OC reports of both. The GTX275 seems to be clearly in the lead. Reply
  • SiliconDoc - Saturday, June 06, 2009 - link

    " Guru3d has OC reports of both. The GTX275 seems to be clearly in the lead. "
    --
    This is red roosterville. Compare the special edition from manufacturer ATI 4890 to the standard or sub OC GTX275, then spin it up more for the red roosters with special custom game profiles, resolution and game settings, and leave PhysX ON even if the game doesn't use it.
    Post the massively biased results and provclaim ATI the overall superking winner.
    Allow your red rooster fanbase and anyone else enjoy the fantasy, while lying as much as possible, and apologizing every time the bias is pointed out by a poster, claiming you didn't know, you'll fix it, that's a good question, you'll get to it, you didn't mean to compare Oc'ed ATI to stock GTX275 - etc etc etc .
    --
    That's why other reviews so often show the GTX275 way ahead. Not every single one - there are more red rooster stations about, but hey, some people like Derek just can't help themselves.
    Reply
  • joeysfb - Thursday, April 30, 2009 - link

    How to be fair?.. Overclocking is subjective in nature... So if Derek's card can overclock to 1G/1.2G and the one i bought can't do it. What's next?...

    This article is about 4890, GTX275 will have another article for itself. Beside, you are pretty fix that GTX275 is the better card anyway...
    Reply
  • ira176 - Wednesday, April 29, 2009 - link

    I've heard the rumor that the Radeon HD 5000 is around the corner, but will ATI incorporate 40 nm tech into the HD 4870 and 4890?

    Wouldn't it be a pretty neat card if Sapphire could get their hands on an HD 4890 with 40 nm tech and the Vapor-X cooling solution!
    Reply
  • Shadowmage - Wednesday, April 29, 2009 - link

    ... you could have presented the graphs in a much more readable manner. The only thing you were really doing was finding the Amdahl's Law curves for the part.

    Watch out for sentence fragments in the future too :)

    As an aside, usually mainstream hardware reviewers are absolutely horrible and incompetent at overclocking, so it's refreshing to see some results that actually match what end-users have been reaching on various enthusiast forums (~1GHz core clocks on stock air).
    Reply
  • DerekWilson - Wednesday, April 29, 2009 - link

    Thanks for the suggestions. Can you email me the sentence fragments :-)

    And actually we'd probably see more overclocking articles if I didn't take it seriously... I'm not the best at it, but I do what I can.
    Reply
  • corporategoon - Wednesday, April 29, 2009 - link

    Quite a few folks in here are talking about messing with voltages - how do you do this? I have a 4870 with a thermalright cooler and I'd love to mess with voltages to get some extra performance out of it, but have had no luck searching for a utility that'll let me do this. Reply
  • DerekWilson - Wednesday, April 29, 2009 - link

    the ASUS card we tested actually comes with a utility to tweak its voltage. there are some hardware mods out there as well ... if you're really hard core you can go check out mvktech.net and download some bios readers/writers and editors and really go crazy (and possibly destroy your card).

    but there are options.

    our tests were done without voltage mods.
    Reply
  • walp - Wednesday, April 29, 2009 - link

    Awesome test!

    I bought the 4890 for three reasons:

    -Its funny to overclock and see the range soooaaAAaaaar!

    -Its relatively cheap for top of the line performance (when overclocked to 1000\1150 @ 1.43V ^^) as you can clearly see!

    -Its totally compatible with the accelero s1 which currently keeps my GPU below the 64°C at full load furmark. And its soooo silent! Gotta love it! 19 bucks for a kick ass cooler!

    Enjoy the silence, and powah! :D

    And when the games become more demanding, I will buy another one! (hopefully a lot cheaper, and a lot more developed x-fire drivers!)

    Cause, I can play Crysis 1920x1080, very high, everything maxxed in Catalyst 8x AA, 16x AF etc. ~40-50fps AWESOME-O! :D
    (4.4GHz E8500, 4GB ram)

    Its a pity though that it costed me 2500kr incl. shipping (~300$) here in sweden, but its worth every Krona! :)
    Reply
  • kmmatney - Wednesday, April 29, 2009 - link

    Thanks for letting me know that it's compatible with the accerero S1! I would love this card if it were a little more quiet. Is this the one you have?

    http://www.newegg.com/Product/Product.aspx?Item=N8...">http://www.newegg.com/Product/Product.aspx?Item=N8...

    Where did you get it for $19? I see this one for $19:

    http://www.newegg.com/Product/Product.aspx?Item=N8...">http://www.newegg.com/Product/Product.aspx?Item=N8...


    With my HD4890, there's a lot of heat coming out the back vent, so I'm a bit leary about using something like this, but if it makes the card cooler and quieter, then I'm all for it.

    Reply

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