128-bit bus GDDR-5 vs. 256-bit GDDR-3

I've been browsing the forums for quite some time now and when I read about gddr-5 memory I got the impression that is was the almost the same thing as doubling the memory bus. I'd be grateful if someone could enlight me on this topic.

 

You are correct. It is the same since GDDR5 transfers twice the amount of data compared to GDDR3, hence it would equivalent to doubling bus width.

 

at the same clock rate...........

 

Yes at the same clockrate.. It's allright if you have a 128bit bus GDDR5 card but its awesome if you have a 256bit-bus card but sadly in the mobile world, there isn't one yet in a laptop although there are some cards which can use GDDR5 like ATI 4870..

 

If you have choice between exactly same specs except GDDR5 + 128 bit // GDDR3 + 256 bit, the former combination should have the same performance as the latter, but with lower energy requirements (increasing bus-width increases energy demands I think). Only GDDR5 I've heard of mobile gpu-wise is the GTS250m in a toshiba qoosimo or something like that.

 

So there are no disadvantages to gddr5 compared to gddr3, such as increased energy consumption? This makes the difference between gddr2 and gddr3 memory seem comparably small.

 

There are no cards that use GDDR2. And GDDR5 would consume less power at similar speeds than GDDR3.

 

oops! I did of course mean ddr2 memory, do excuse my insolence.

 

GDDR5 has higher latency, which will affect performance slightly, but I do believe it would be a very minimal difference. The advantages of using a 128bit bus such as lower power consumption and less heat far outweigh the maybe 2 fps that would be lost. Not to mention cheaper cards, since 128bit bus manufacturing process is much cheaper.

 

Avoid any graphics card with DDR2 memory at all costs. GDDR3 vs GDDR5 may not give much of a difference, but GDDR3 is miles ahead of DDR2.

 

... didn't everyong just say gddr5 is twice as fast as gddr3???

 

I think GDDR3 is twice as fast at same clock speeds as DDR2/DDR3 while GDDR5 is twice as fast as GDDR3 as same clock speeds... however I could have gotten that completely wrong

i.e. everything else being the same
200mhz GDDR5 = 400mhz GDDR3 = 800mhz ddr2/ddr3

 

Yes, but with half the bandwidth, so effectively, they are the same speed.

 

That part isn't true.
GDDR5 and GDDR3 are different chips. GDDR5 has double the bandwidth of GDDR3 per megahertz. To compare them, you could say GDDR5 is quad-rate even though it is not exactly the same, so you are correct.

On the other hand, GDDR3, DDR3 and DDR2 are another thing. GDDR3 and DDR2 are basically the same thing, GDDR3 has been modified (by ATI btw) to requiere less power and thus have a smaller heat output then DDR2, allowing higher frequency (1200mhz X2 versus 667 X2 on DDR2).

For a reason I have no idea why, graphics card manufacturers often write GDDR2 rather than DDR2 and DDR3 rather than GDDR3. GDDR2 has only been used on the Geforce FX 5700 and FX5800. I don't think DDR3 has been used on graphics card very much, except maybe the mobility Radeon 46xx

 

agreed. I think Geforce Fx cards are for professional use, so ddr2 is more stable (heat issue)

 

It's only half the bandwidth if you get a card with half the interface bandwidth.

YOU SIR ARE WRONG!!!!

 

Damn, I just got told.

 

In fact, the same card equipped with GDDR3 consumes less than the same one with GDDR5. That is the case of the 4830 and the 4860. The reason the Envy 15 uses the first with GDDR3 is because the heat and consumption is lesser on a GDDR3.

The 128bit is easier and cheaper to produce, but GDDR5 is much more expensive to equip.

The GDDR5 memory runs two times faster than GDDR3, considering that it is the same clock speeds and memory speeds and shaders.

If both cards only differ on GDDR3 vs GDDR5 the second gives double the performance (in theory).



Now, as for the OP's question.

A 128bit GDDR5 cards performs SIMILAR (not equal) to a GDDR3 256bit.
Depends on what you are doing that the difference will be bigger or smaller. On heavily textured areas IIRC the bigger bus sees an edge, on the rest the GDDR5 will match the GDDR3.

The power consumption differences are mostly on the architecture, if it is a 40nm card it will consume less than a 55nm one.

GDDR5 will add more heat and consumption than GDDR3.

A bigger bus consumes more than the smaller one.

It is a matter of balance. If you ask me, get GDDR5, more future proof, and the faster speed does pay.

 

No, this is incorrect. GDDR5 consumes less than GDDR3 - just like how DDR3 consumes less than DDR2 for system memory. Also, the cost benefit is higher since GDDR5 on a 128-bit bus is cheaper than GDDR3 on a 256-bit bus.

http://www.tomshardware.com/news/GDDR5-dram-hynix-gigabit-memory,6634.html

"Compared to the currently popular GDDR3 memory, GDDR5 memory running at 1.5 V already offered an approximate 20-percent improvement in power consumption."

 

On the 128 vs 256 I agree. It is cheaper.

But the reports we got from the GDDR5 vs GDDR3 on the HP Envy 15 Owners Thread (somewhere between 2xxx posts) it was said from an official source that the 4860 heated more than the 4830. Conclusion, they are the exact same GPU, built on 40nm, same shaders, same everything, different memory. Logic says GDDR5 heats more than GDDR3 due to the increased speed.

 

The clocks are a lot higher on the HD 4860. GDDR3 on the HD 4830 is supposed to be at 800MHz, but GDDR5 runs at 2000MHz effectively. Along with higher shader and core speeds.

 

Due to the increased speed on the GDDR5.

 

My previous post pretty much summarized the difference. The fact is that when you compare technologies at similar speeds, GDDR5 consumes less power than GDDR3. By increasing clock speeds across the board, of course there is an overall increase in power consumption. You can't compare the two (HD 4830/60) directly because the performances are vastly different due to the clock speed differences.

What would be a fair comparison is comparing the HD 4860 with an identically clocked version but with 256-bit GDDR3 (doesn't exist). But if it did exist, the 256-bit GDDR3 card would consume MORE power than the HD 4860 (128-bit GDDR5).

 

Yes. That is what I said. But I think my point came out not-well-explained. What I was trying to say is, considering all specs the same, GDDR5 consumes more than GDDR3, but 256bit consumes more than 128bit. So it is to look it this way.

In heat consumption
GDDR5>GDDR3
128<<256

So the 128bit is less producing, but not by THAT great difference, since the faster clocks of GDDR5 produce more heat. But there is a difference. And since no 55nm is available for laptops with GDDR5, only 40nm, the 128bit will win as less heat production, but this is achieved due to the smaller bandwidth and the smaller process, not because the GDDR5.

 

I get what you're saying and I disagree. What I'm saying is GDDR5 < GDDR3 with comparable clocks. If you have two identical GPUs in terms of manufacturing process, clock/shader speeds and everything except bus width/memory type, 128-bit and GDDR5 both will contribute to lower power than 256-bit and GDDR3. Why? Well just look at the power design of GDDR5 and compare it with GDDR3. None of your examples reflect this because there are many other factors that have been changed. Read the link I posted above.

 

Then I dont get it, if it runs cooler, consumes less, it is cheaper, it is better, faster. Why is it not fully used?

 

Production output is low. When more manufacturers switch their plants to GDDR5, then we'll really see it in all cards. Its cheaper to produce GDDR5 but costly to switch... in the long run it will be better, but companies can't just change all their production instantly.

 

So there are no downsides of the GDDR5?

WOW, I am terribly sorry for my argument that seemed pointless and non-based. My apologies.

And thank you sgogeta4 for correcting me, it is great to know that there is an actual technology that has no downsides...

EDIT: "You must spread some Reputation around before giving it to sgogeta4 again." I cant for the moment to thank you...sorry

 

Interesting. What doesn't make sense though, is that I've heard that the new 5750 and 5770 cards are going to use GDDR5 memory with a 128 bit bus while the 5830 will have a 256 bit bus but only GDDR3 memory.
I mean if that is what's going to happen who would want to buy the later?

 

If I recall correctly the 5830HD has more shaders if not mistaken. It is the GDDR3 version of the 5850HD which uses GDDR5. And both use 256bit.

 

No, they were the geforce 5 series, and kind of crappy against the competition. These were around about 6 years ago. I actually have a working FX 5800 and it uses GDDR2. Never caught on and was quickly replaced by GDDR3 because it sucked so bad.

 

http://www.gpureview.com/show_cards.php

Use this to compare specs of stock video cards.

 

I cant seem to find the 4000HD Mobility series on that website...

 

Weird, swear it was there before. Unfortunately it's focus is desktop GPUs though. Maybe there will be another resource (other than notebookcheck).