killnine

The use of DDR5's higher speed negates the need of the bit-width throughput of a 512-bit bus.

Both are independent solutions to the same problem: memory bandwidth.

You can get the same bandwidth by using a higher memory clock speed and a lower bit width OR you can use a slow clock speed with a higher bit width. You don't need both and its a waste of money to do both.

This is a fundamental manufacturing issue and right now its much cheaper to integrate ddr5 into boards than manufacture a 55nm chip with a 512-bit bus. You don't sound like you have any background in this issue and you don't sound like you understand the economics of electronics manufacturing. So before you go and spout every article on fud and inq, open an electrical engineering textbook (http://www.amazon.com/Computer-Organization-Design-Hardware-Interface/dp/0123706068/ref=pd_bbs_2?ie=UTF8&s=books&qid=1210992906&sr=8-2 or http://www.amazon.com/Computer-Architecture-Quantitative-Approach-Kaufmann/dp/1558605967/ref=pd_bbs_7?ie=UTF8&s=books&qid=1210992906&sr=8-7).

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QuickS

I am an electrical/computer engineer major actually. Nice try at trying to sound smart BUT I would put money on it that it cost AMD/ATI more money to get 512MB of flying fast GDDR5 than to have semi fast GDDR3 and a 512bit bus.

Melcar

Actually, it is expensive. AMD said so when the HD3Ks came out (comparing them to the HD2900s). It probably is not that much, and at this point I bet it's more expensive to stick GDDR5 modules in there. Also, it's been said that it's rather difficult to fit such a big bus on a small die.

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Halo2Vista

than put that major to good use, and go work for Intel, AMD, or Nvidia, or any other company that interests you.

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rx7racer

Well, by the time you figure up the increased layers to the PCB and the increased bit width on the die and implement it the cost all around actually would be a bit more than just a 512MB GDDR5 ic.

Killnine is right, and it boils down to efficient econimics on what will cost the least and produce the most. If they went 512-bit then the 4870X2 would easily be a $600+ card and right now they want to be a bit more competitive so they are making the necessary cuts while maintaining the incredible bandwidth shown by the 2900.

I can't wait, gonna jump on the 4870 asap

RayvinAzn

You don't sound like one. At least I like to think people with any sort of reasonable background in engineering would sound...well, not like you at any rate.

Everything I've read leads me to believe that a card using a 512-bit memory interface is much more complex and difficult (and consequently more expensive) than getting a decent amount of a new type of memory on a card. New memory involves very little tweaking on the part of ATI to support different types, so they can put out GDDR3/4/5 versions of these cards with a minimum of fuss, while a more complex overall architecture around a 512-bit bus is going to be more of a pain not only to implement at the higher end, but also to cut back on for lower end versions of the card. Given the flexibility ATI is trying to lend Crossfire, cross-compatibility is essential to their strategy, so designing two different architectures based around the different interfaces might also cause more problems than it's worth. There's also heat/power consumption, with a more complex PCB, more traces, etc. the card is going to run quite hot, something ATI seems to have steered away from since the X1800/X1900 and HD2900 series.

Just my thoughts anyway. If you have something more intelligent than bragging about something neither you nor anyone on these forums can prove or disprove and typing stuff that has no actual substance to it, I'd be more than happy to read it.

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Ikon

Qimonda is currently producing GDDR5 memory chips from 3.8-4.5GHz.
Who knows about others.


144GB/s bandwidth is probably more then enough.

Jay1ty0

will those cards be super power hungry?
Will a Odin 550W GT handle a HD4870??

The Duke

With 4x18a 12v+ rails, it should.

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QuickS

No offense but you don't sound too smart yourself.......
Please type in paragraph's, enough with the run on sentences. What I was trying to say is that the way that Nvidia is designing their GT200 card is the best way to go about it IMHO. A 512bit bus and fast GDDR3/4 would be much better than spending loads of money on new GDDR5 technology that hasnt even proven it's worth yet.

Also, who ever said anything about using a 512bit bus on their low end? That would be extremely foolish, they could always stick with the 256bit bus with their low end. Temperature's have never been a problem with the bigger 512 bit bus. The biggest contributer to high temperatures is the process that the core is built on and the heatsink/fan they choose to use. (duh!) Please do some reading before you go around flaming making yourself sound like an idiot.