Overclocking Extravaganza: Radeon HD 4890 To The Max
by Derek Wilson on April 29, 2009 12:01 AM EST- Posted in
- GPUs
Cranking GDDR5 All the Way Up
The first stop on our overclocking tour is in the memory subsystem. We will be increasing the memory clock frequency which reduces latency slightly and increases bandwidth significantly. The stock clock speed is 975MHz with 1ns devices (which means they are rated at 1GHz). AMD mentioned that signaling and interference (caused by the graphics hardware) are bigger problems with 1GHz GDDR5 than actually running the memory at that speed, which is why they went with the 25MHz lower clock speed.
Even with the 975MHz default clock speed, we already have a data rate of 3.9GHz. Which is pretty intense. We found in playing with ATI's built in overclocking tools (overdrive), we were able achieve stable performance at the maximum clock speed the driver allowed: 1200MHz. Doing the math gives us a massive 4.8GHz of data rate. This means, with a 256-bit wide bus, we're talking about almost 154 GB/s of bandwidth. This is more memory bandwidth than the NVIDIA GeForce GTX 280 and just a little less than the GTX 285 (which both use GDDR3 but on 512-bit busses).
So armed with 1.2GHz GDDR5, what can the 850MHz core of the Radeon HD 4890 accomplish now? Let's take a look at percent increase in performance per game when just increasing memory clock.
1680x1050 1920x1200 2560x1600
Apparently not that much more, even at 2560x1600.
Because our tests are not 100% deterministic, there is some variability in our results. Generally, this is very low, though it does vary from game to game and benchmark to benchmark. We have a hard time calling anything less than a 3% difference significant, as it could be due to fluctuations in the tests. These numbers may indicate some positive change in performance, but not one that would matter. At 2560x1600, only Call of Duty showed a performance improvement that mattered. And this is from a 225MHz overclock (just about a 23.1% increase in clock speed), which is pretty large.
There really isn't a huge need to delve into the raw numbers here, as they are just not that different. We'll hold off on that until it matters. Next up, we're going to look at increasing only the core clock speed.
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gold333 - Monday, May 4, 2009 - link
Guru3d has OC reports of both. The GTX275 seems to be clearly in the lead.SiliconDoc - Saturday, June 6, 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.
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...
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!
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).
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.
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.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.
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! :)
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.