What is it exactly that holds back video card ram from o/cing any further?

[kami]

Say you have some 4ns DDR memory, and you get to a certain point (let's say 550MHz) where artifacts start showing up in games, so you clock it down 5-10MHz for safety. Now, what exactly is causing this?

1. Is it heat? This would mean that a 4ns chip would somehow get hotter at 550Mhz than a 3ns chip would since the 3ns chip can go well beyond 550Mhz.
2. Is it the ns rating that causes the artifacting? If it's the ns rating, then what's the point of cooling the RAM?

I'm a little confused on the whole thing...

Also, does increasing the AGP voltage let you overclock more (and produce more heat I'd imagine). The mobo I just ordered supports it so I'm just curious.

 

[RedShirt]

Its both.

The hotter something gets, the more resistive it becomes. Signals may be able to travel freely at a certain tempature, but at a higher tempature, the same signals may not make it though, some will be lost due to the increase in resistance.

The speed rating of the chip is pretty much like a MHz "rating" for processor. For instance, a GigaHertz processor has a clock cycle of 1ns. For some reason, they rate RAM by the ns instead of hertz.

Processors can be ran faster than their rating and RAM can be ran faster than its ns rating.

And, I would leave the voltage alone It may help, but you could do some harm also... But I'll let someone else field that question since I've never done it myself.

 

[kami]

OK that's a good analogy and makes sense. 4ns = 500mhz ddr right? So how do ns ratings work? what would 3.9ns equal in MHz? (how much of a step per 0.1ns)

 

[zzzz]

what would 3.9ns equal in MHz? (how much of a step per 0.1ns)

1/3.9*10^-9 in Hz
divide by 10^6 to get Mhz

 

[kami]

Originally posted by: zzzz

what would 3.9ns equal in MHz? (how much of a step per 0.1ns)

1/3.9*10^-9 in Hz
divide by 10^6 to get Mhz

thanks