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4870 memory clock question

Last response: in Graphics & Displays
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September 17, 2008 6:18:41 AM

Greetings! Looking at purchasing all the goodies for a new build within the next couple days. Would Love to get the 4870x2, but not thinking i want to shell out THAT much ... After scouring the forums, several of the resident experts are recommending the 9800gx2 ... but some of the same experts have issued warnings of lack of driver support for x2 models ... so, being partial to single card solutions anyway, i'm kinda not liking that option.

Which leads me to my main question, since i seem to keep coming back to the 4870; of all the flavors, several have slight core clock OC's (780 - 800 vrs 750 stock) is that slight of an OC going to make a difference, and if i don't want to purchase a special separate gpu cooler setup, would i be able to achieve similar results just oc'ing it to that myself? (i know that will be influenced by my case and general cooling and other component selection, but in general...)

And secondly, i have not noticed any mention of Memory clocks. There are a HUGE variety of variations on this within the many 4870's out there; 900 mhz seems to be stock and it goes up from there to 1800 mhz, 3600 mhz, even 4000 mhz, ... and one listed @ 1100 mhz x2 ??? How big of a difference is this setting going to make? That seems like a LARGE gap in specs?

I got these from checking New Egg ... and i read several replies to a post about the 1 Gig versions of the 4870 ... which were anything but favorable it seemed ... but i must fall into the crowd of gullible people that will fall for that marketing ploy :whistle:  . i plan to game at a minimum of 1920 x 1200 and want eye candy MAXED, and memory seems like a huge factor in that (though, i recognize what one of you posted about being choked by the 256 bit, but i'm hoping the DDR5 will help with that).

Thanks in advance for your combined knowledge and input!
September 17, 2008 7:07:09 AM

Dude I own a saphire 4870 reference design (stock dual slot cooler) and I must tell you I'm very happy with it. About the frequencies of GPU/Mem, I'll give you the following. First of all, make sure the one you buy has GDDR5 memory (I think I saw somewhere a version with GDDR3). The clocks are 750 for the GPU (Which I uped to 820 without changing voltage and it runs like a charm. Higher frequency IS possible with a bit of effort). The memory runs at 900Mhz (effective 1800Mhz) but GDDR5 is effectivelly "quad pumped" so it has the bandwith and speed of 4 times the 900Mhz which is 3,6Ghz (which is not true as it runs at 1800, but it performs like 3,6Ghz).
I Oced the mem on my card to 1050Mhz making it 2,1Ghz (which performance-wise translates to 4,2Ghz) with no problem. I've seen ppl go as far as 1100 (4,4Ghz). With aftermarket cooler you can OC this puppy all the way to heaven!! Also, there are on the market 4870 with custom coolers which don't vent air out of the box. I'd recommend against that as this card runs pretty hot and will heat up everything inside your box unless it vents the hot air out. I game at 1920x1200 and although my sys sucks, I can play everything maxed (almost) except crysis. The 256bit bus might sound restrictive but when running Gddr5, the effective bandwidth is Huge, almost as much as as the GTX280. I'm not a fanboy as I also own Nvidia cards, but this card is impressive (for the price). Good luck making your decision!
September 17, 2008 10:11:24 AM

Yeah the memory speeds are just confusing because some places list the actual clock rate while others list the effective rate. 900mhz is stock, easily upped to 1100mhz through the CCC.
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September 18, 2008 1:25:29 AM

Thanks for the responses!

So basicly, if the memory clock is 900 mhz, or any multiple of 900 mhz, then it is probably just the data entry people not understanding, or perhaps purposefully misrepresenting, i.e. 1800 mhz, or 3,600 mhz?

But, the 1100 x2 is probably really oc'ed (but, again, they didn't actually understand how the DDR5 works, as that would actually be 1100 x4, or 4,400 effective mhz?) And the 4,000 mhz, is probably upped from 900 to an even 1,000 mhz?
September 19, 2008 3:16:18 PM

1100 is probably OC'd yes. You can OC it yourself to that speed with no problems, so I wouldn't pay more for a company to do it. I don't know about the x2 bit, maybe it was a 4870X2 you were looking at? It's essentially 2 4870 GPU's on one board.
!