8600m GT: DDR2 vs. GDDR3

I'm not even sure I phrased that properly, but here's my question: I understand that the GDDR3 8600m GT is superior to its DDR2 brother, but just how superior is what I'd like to know. Please explain the performance increase that should be visible between them, and don't be afraid to get technical.

Thanks Guys (And Girls!)

 

Actually the thing is GDDR3 can go for higher memory frequency rates than what GDDR2 can and in addition to that GDDR3 consumes less power than GDDR2....

Having said that it is not quite easy to see any visible performance difference between a card running on GDDR2 and a one running on GDDR3 provided they run at the same memory clock (and GPU clock too) and same bus width too except for an increased battery life with GDDR3....

IOW for comparison of 2 GPUs it is the GPU clock, the memory clock and the bus width that really matters for any graphics card as such being all other factors equal

 

So is their really a substantial difference in performance?

 

Like I said - nope.... Always the higher clock rates are the better ones.... Only thing is better battery life with GDDR3...

 

Yes there is a 10-15% gaming difference due to the clock differences. THe gddr3 can overclock signifigantly more to leave the gddr2 in the dust.

 

Well if there is not much of an increase in gaming performance, then how come my Asus G2S-A1 w/GDDR3 8600 destroy my Inspiron 1720 w/GDDR2 8600?

 

well the memory bandwidth difference is quite significant.

the ddr2 is 12.8gb/s
the gddr3 is 22.4 gb/s

thats is the ONLY difference between the two cards.

 

where did you get that info?

 

And this means...?

 

It means gddr3 is more powerful by the amount I said. It will run your games marginally better than the ddr2 and will overclock alot moe than the ddr2.

 

Alright, Thanks!

 

The memory bandwidth is dependent on the memory clock I say it again.... I believe you got this info from the Geforce 8 wiki.... It is indeed correct only if the GDDR2 card runs @ 800 Mhz and the GDDR3 card runs @ 1400 Mhz which I believe are the maximum possible clocks that GDDR2 and GDDR3 respectively can acquire...

But usually notebook GPU memory clocks are not so higher and hence the memory bandwidth will be usually lesser than those figures.... I still can confirmly say that a 800 Mhz GDDR2 card and a 800 Mhz GDDR3 card have the same memory bandwidth.... But one advantage with the GDDR3 is you can overclock it easily and safely.... But with notebooks overclocking should only be attempted only if you have sufficient cooling mechanism....

 

actually i got it at gpureview.com, and of course they will be the same at the same speeds, but like he said you can attain much higher clock speeds.

 

Those are the stock memory bandwith's of each type, and are the memory bandwith's that are found on 95% of notebooks with those card types. Real world gaming difference is usually around 30% by all the figures I've seen, up to a maximum of 75%, though it will always be at least 10-15%. The only difference between the two types of memory are the achievable clock speeds (thus the difference in stock clocks) and the power consumption/heat output at identical speeds (which favors the GDDR3 as noted in previous replies).

 

Where did you see this?

 

Perhaps I should have made it clearer, that is the theoretical maximum if the game is completely bottlenecked by memory bandwith.

 

so, he should go for the gddr3 ?
because he can get easily the same performance with gddr2 if he uses stock settings

 

Hmm? No, the DDR2 at at stock settings will never give the same performance as the GDDR3 version at stock settings. I'd recommend going for the GDDR3 version if the price differential isn't too great.

 

I'm getting such mixed resposes here! Some people say there is virtual no performance difference an its all in the increased battery life, while some are saying there is in fact a notable performance gain... Who do I believe?!

 

There will indeed be a noticeable performance gain, the battery life gain may on the other hand not be noticeable (depending on what laptops you're looking at). What models are you looking at, or have you decided yet?

 

GDDR3 is not faster than than DDR2 by itself. However, since DDR3 can achieve much higher clock than DDR2, GPUs using DDR3 tend to have much higher bandwidth than GPUs using DDR2, resulting in performance differences.

In the case of 8600m GT in particular, DDR3 version has 700Mhz RAM while DDR2 version has 400mhz, which translate in 75% difference in bandwidth, which is a lot. This is especially true since 8600GT has only 128bit bus, and is heavily bandwidth-starved even with DDR3. Even though the actual GPU on DDR3 8600GT and DDR2 8600GT has the same processing power, slow RAM on 8600GT cannot feed information fast enough to fully utilize its processing power, resulting in significant performance delta between these two. DDR3 8600GT tend to perform about 30% better than its DDR2 counterpart in 3Dmark06. And remember, 3Dmark06 is more fillrate dependent than bandwidth-dependent - I expect the real world difference to be even larger.


I think we really need to do comprehensive benchmarks of various laptop GPUs.....

 

As Woodgypsy says if the GDDR3 version runs at a 700 Mhz clock it should definitely show a performance increase compared to the GDDR2 version which only runs at 400 Mhz...

 

I remember there was a source game test using both versions somewhere on the forum? The DDR3 version being about 27% faster with AA and AF - where the ddr2 really starts to take a kick in the nuts. I think with just high settings no AA/AF that the difference was more marginal. But I'm not fully sure. Personally I'm only going to be playing Dawn of War on my 8600GT so the DDR2 issue isn't even AN issue. But it'd be interesting to see the difference on titles like Bioshock and the like.

 

Yep, it was a CS:S source test, I believe done by mastercheif. It showed around 28% difference at 1440x900 I think with high settings.

 

It's a considerable loss, but not catastrophic - I think playing at lower res and without the AA and AF, the gap isn't going to be as significant. Though, of course, a 28% difference would be critical if you were hovering around the 25-30fps playable zone on the DDR3 model...but still.

All in all, considering the bargin price of the Vostros right now, I think it's a worthy trade off...

 

It is near the same performance loss of getting a 64bit version

 

do people still argue about ddr2 vs gddr3?!

 

No, it's not.

 

Actually, it is, as it's almost half the bandwidth, which is what a 64 bit memory bus would result in compared to 128 bit.

 

But you have levels of overclockability with the ram. Anybody would rather have a 128-bit DDR2 8600GT then a 64-bit DDR3.

 

Yes, the 128-bit DDR2 is slightly more powerful, however total overclocking is pretty much the same, as GDDR3 overclocks a lot better than DDR2.

 

Yeah I know it scales better but the point being there's zilch you can do with a 64-bit card, but with DDR2 ram at least you have the option of boosting performance...

 

Remember that your bandwith equals the memory clock speed times the bus width. I.E. you can make up for a 64-bit bus by overclocking the memory, just like if you have DDR2 you can OC to get better performance. So you can boost performance the same way in either situation.