6600gt 2.0ns memory question

[Silversierra]

Ok, I have a 6600gt that has samsung 2.0ns memory. I read an article that said that you can use the ns rating to figure out a memory's max overclock. I figured mine should only go to 1000mhz with 2ns memory, but my memory can oc to 1.16ghz stable and I've had it as high as 1.21ghz with some artifacts. So how can the memory go that high? Shouldn't it be limited to 1000mhz?

Side note: How do you know when you've reached your core's limit for ocing? Does it just lock up? I went to 564 and had no problems.

 

[imported_Kensai]

It's fuggers up during GPU intensive applications. I also like to tone it down a little from it's max.

 

[Silversierra]

Kensai, what are you referring to? The core or the memory?

 

[Lonyo]

I find the GPU just locks up when it's been pushed too far.
Memory artifacts when it's gone too far.

If it locks up, you know you need to back off.

 

[Goi]

the 2ns rating is probably the cycle time, which is the clock period. Frequency = 1/clock period, so with that rating, the memory is rated to go to 500MHz, or 1000MHz effective since it's DDR. When you're exceeding that value, you're overclocking the memory, and nothing is guaranteed. With onboard memory, sometimes you won't even reach the rated clock speed due to board design and how the card manufacturers time the memory. Case in point - the early 9700 Pros which had fast rated memory but were clocked slower, and could not reach their rated clock speeds consistently.

 

[sellmen]

Originally posted by: Silversierra
Ok, I have a 6600gt that has samsung 2.0ns memory. I read an article that said that you can use the ns rating to figure out a memory's max overclock. I figured mine should only go to 1000mhz with 2ns memory, but my memory can oc to 1.16ghz stable and I've had it as high as 1.21ghz with some artifacts. So how can the memory go that high? Shouldn't it be limited to 1000mhz?

Side note: How do you know when you've reached your core's limit for ocing? Does it just lock up? I went to 564 and had no problems.

The 2.0ns is just a rating; Samsung "guarantees" that the memory can reach 1000mhz. It isn't much different than CPU ratings - a 2ghz AMD CPU may be capable of running at much higher clockspeeds.

It's hard to tell exactly how high you can overclock your GPU/RAM. When overclocking a CPU or system RAM, you can use programs like Memtest86 and Prime95/SuperPI to test stability - there are no such programs for video cards. There are "artifact testers" such as ATI Tool and a few others, but they aren't perfect tests of stability.

Most people test by looping a benchmark like Unreal Tournament or 3Dmark for a few hours and looking for artifacts. Again though, this isn't a perfect test - there are people who had their "stable" overclocked video cards artifact when playing Doom III, which apparently stresses modern GPU's in new ways.