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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  • PrinceGaz - Wednesday, April 29, 2009 - link

    Interesting certainly, but when I read Overclocking... to the max" my first thought that a large tub of LN2 would be used :p Reply
  • DerekWilson - Wednesday, April 29, 2009 - link

    heh ... i'd love to play with some liquid nitrogen. that'd be great fun. i don't think we're going there anytime soon though. Reply
  • Veteran - Wednesday, April 29, 2009 - link

    Why didn't you guys play with the fanprofiles? Added some VGPU with 3th party software? Just went to the realy maximum of the card. It would be amazing to see the results of that. Using 3th party software shouldn't be any limitation to overclocking if you ask me. Reply
  • DerekWilson - Wednesday, April 29, 2009 - link

    We did set the fan on 100% manually all the time. Sure, it's a leafblower at that speed, but we wanted to keep it cool. Sorry I didn't mention that.

    It is possible to get some 4890 cards higher, but this wasn't an article for the hardcore overclocker. Rather we wanted to talk about what the average user can do out of the box by clicking a few buttons in the driver. Which, in my opinion, is more impressive than if we'd gotten an extra couple percent increase in core and memory clock speeds.

    Not that even I wouldn't be interested in knowing how fast you could get one of these beasts ... It's just a different article than the one I wanted to write here.
    Reply
  • SiliconDoc - Saturday, June 06, 2009 - link

    It will be a nice day when you don't have to apologize ten times in every ati vs nvidia article for your massive ati biased BS Derek.
    --
    " We did set the fan on 100% manually all the time. Sure, it's a leafblower at that speed, but we wanted to keep it cool. Sorry I didn't mention that. "
    ---
    All you red roosters aren't sorry - the enthusiasts see your charts and head off to redland purchse while your lying CRAP misdirects them ! And you know it - and are sickeringly proud of it no doubt !
    It's been going on forver by you here !
    PERIOD!
    Reply
  • Veteran - Wednesday, April 29, 2009 - link

    The title just imply different things then this review. That's all, i enjoyed reading it and see how the card responds to Core and Mem OC's. But if you use the words 'extravaganza' (very special) and 'to the max' people start thinking about dry-ice/ln2, voltage modifications etc.
    The article is awesome, the title is a little bit wrong
    Reply
  • CyNics - Wednesday, April 29, 2009 - link

    to Derek: have you tried overclocking the GeForce GTX 275, or at least comparing an OC'ed gtx275 with an OC'ed 4890 before coming to such conclusion? Reply
  • DerekWilson - Wednesday, April 29, 2009 - link

    This is a pretty good question --

    These tests and the article took a while for me to put together. I am planning on doing a GTX 275 overclocking and seeing if anything interesting happens. If I get good results I'll put together an article on the subject.

    I tried pretty hard to keep this article on the subject of the 4890 itself and where I made comparisons it was to hardware outside it's price class with the GTX 285.

    No matter how well the GTX 275 does, the 4890 still did as well as it did versus the GTX 285 (and relative to itself).

    If I screwed up and made direct comparisons between overclocked 4890 and GTX 275 or something, let me know and I'll fix it 'cause I didn't mean to. Otherwise I hope that this article is as appropriate as I wanted it to be.

    Once I've also overclocked the GTX 275 I'll have something to say about it's relative value versus the 4890 in that regard.
    Reply
  • SiliconDoc - Saturday, June 06, 2009 - link

    THAT'S AN AMAZING BIT OF BS DEREK !

    " If I screwed up and made direct comparisons between overclocked 4890 and GTX 275 or something, let me know and I'll fix it 'cause I didn't mean to. Otherwise I hope that this article is as appropriate as I wanted it to be.

    Once I've also overclocked the GTX 275 I'll have something to say about it's relative value versus the 4890 in that regard. "

    First you say IF you used a non overclocked GTX275 and screwed up doing it - someone should point it out (because you obviously can't see it in your own charts - right red rooster?) - and if someone points out your massive idiots bias, you'll change it otherwise you won't... THEN YOU ADMIT YOU HAVEN'T OVERCLOCKED THE GTX275 YET ! PROVING ABSOLUTELY YOU DID IN FACT COMPARE IT NON OVERCLOCKED TO THE 4890 SPECIAL MANUFACTURERS EDITION SENT TO YOU !
    -
    SO WHAT THE HELL DID YOU MEAN BY " If I screwed up and made direct comparisons between overclocked 4890 and GTX 275 or something, let me know and I'll fix it 'cause I didn't mean to." ?!!???
    --
    YOU DID IT DEREK - YOU KNEW YOU DID IT, YOU DID IT "ON PURPOSE" THEN EVEN AS YOU DENY IT AFTER BEING QUESTIONED, YOU ADMIT IT INCRIMINATING YOURSELF !
    YOU EVEN ASK THE QUESTONER POINT IT OUT WHEN YOU DID THE CHARTS AND THE TESTS HERE !
    MY GAWD!
    --
    Dude, if you think your BS is even passable, THINK AGAIN !
    Reply
  • SiliconDoc - Saturday, June 06, 2009 - link

    Yes, our great masterous "fair" and "unbiased" reviewer Derek
    .
    DOESN'T EVEN KNOW WHEN HE IS COMPARING OC'ED SPECIAL MANU. TO STOCK !
    .
    .
    WHAT a genius! Keep that boy hired ! Must be worth a whole 50 cents an hour, if that !
    Reply

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