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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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 :pDerekWilson - 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.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.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.
SiliconDoc - Saturday, June 6, 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. "
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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!
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
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?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.
SiliconDoc - Saturday, June 6, 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 !
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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." ?!!???
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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!
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Dude, if you think your BS is even passable, THINK AGAIN !
SiliconDoc - Saturday, June 6, 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 !
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WHAT a genius! Keep that boy hired ! Must be worth a whole 50 cents an hour, if that !